GB2339620A - Measuring real and imaginary components of electrical power - Google Patents

Description

I I 2339620 MULTIFUTNCTIONN A-DA-PTIVF 'CONT'I"RO:,S _FI_R TI-PSW7TCHES

CA-D BCVrIROUND or Tjl!V-PNTTON:

-.cad -a-,Dc'nangi-,.i_g transformers -ere n-giner vo-cages are q ss or; si-,bs- or.s w'.'- bf MS.

e ora suop- subtransm-issio-) S7Stel sutstaticns s up p 1 y 41 n a regulated n, tu e = ed _4 a t e v o I a c e s d -' s t r _i!D u t J_ c n 1, 1:,, e s.,_lternat_ivelv load somietinies used with fixed ratic voltage _-E-_Iuc_4n_g o' load 41_-a)changing ransfonmners at distrj - -t 4 e bu on stat-:o s h c o i-, -I) n a t i c. P. s u. n n 1 -i e s r e gu 1 a t- e d v o I Uq e s o e a c h a s 0 o a o g r) c w d s ihn u t I', o -. I i n e s Load ta.nchana_Jng --re""ators are also -- fo-nd I Z e -=A, E? a I a e " 0 1 n.- z s on 1 o n g e I- d _J s i b u t.L o in I i n e s for Z-e-ecu atio___ 0_ t,E.,70 i tageS, T_-_-ernediaza volzal-jes are stepped e-own to lower voltac:es, sen,--ing users of electric powe_r, ')-v a-iong the distributio.r lines.

i-Lu,to,t-rar)_sf,c,=,,.ers wit'n, switched. taps for von-, tE -s s-Lmcly --eferred to as Ire.c-diators7l. -lie ',ern transformer," is com-nionly used to distinguis-'- t_-,,7o w-indilng vcl- aae chang-ing transfornmers with switched taDs for voltage regulation from cnanginc. transformers. Ttese conven_tzo-s _xed ratio volaqe w_11 be --"o--,lcwed hereil n COntrols for load tap c-'anging transfo=ers a-nd atc,-s generallv have f-'eatures as called for in AN7Si standards C37. I 5-1_986 regula-10--r-s and C5"j.1-2. 10 -f-or LTC transformers. The standards re-,,:----s to settable bandwid-Lhs o---," uD to 6 volts tota-I bandwidth, around an also settable center voltace. One of two t-,rpes o' ou-c-hand timers 4 -enerallv sur)-olied, each having a time out value set-table -,.:ID -0 120 seconds a-'ter w,'L_-',ch a raise or lower tap posit-ion co=a-nL-'l _- _Ls made to 1"Dotor driven, tap's-witch-es. A -first type of --r.

-er times lineariv,;he-n7e or below the band and rese-s JmmedJately wenever voltage is abo returns to within the band. A second 'k-nown. as integrat-i-na zimen- --mes u.:) 1 -2,early whenever -he vo'i tage -s outside t-he band, and times dcwr, at the sa-me rate whenever the voltage is within the band.

SW4 tch life is -found to be denendent on Tap oceration and c n t l'i e S c u, a r e o f c ur.- e r. t e v e I s e a ch- t i -,. -3 th e s,.,,, f t c h a concern -for users of present art load or)erates. _4 s -h e r e f o controls (LTC's) to atte-mpt to set thle time out value and the bandwid-zh vaj_ues sc as to obtain satis-factorv voIt-aae reaulation vet not --apchanges Jr. a given time. Th' s 4 s cause more -.an a des-ired number of t 2 cftan -Found in practice to be a long, laborious andgenerally --r,s.=-jsfac-ory procedure. Preser-t- art c-Enzral Iv d-es not- take t'Le level of the current into account, except- to b-lock -he tapchanger ent-rey a-bove some selected current level.

Switched power factor correction CaDacitors are also used across t-he secondaries of substation 7 TC trans -_For-ners. Swil tching of these aC4 cap -tors is generally accornplished using cont-rols seoarated -Lrro,-,i LTC transformer controls. This reportedly often results in undesired inte-act--Ions between capacitor switchLng and the LIrC tapswitching operation.

Adaptive Capacitor Controls (ACC-'s) are now available using t-he inventions disclosed in the -oatents a.--d patent applications listed below whi1ch require no setpoints and no h=ltan control. ACC's are used to sitch poletop and padmounted power L L_L L w factor correction -capacitor banks located along power distributicn-l-iLnes. These ACC controls adapt to factors su--h as a) to the line irpedance at point of connection to the distribution line, and b) to the variation in electric customer loads nearby the point of capacitor connection to the distribution line. The result of ACC application to distr-Lbution 'Lines fed by dist-ribution power transformers is improved voltage regulation along the dJILstr 4 bution 4 lines and reduced VAr flow through the dist=_bution substation transf o=ers.

The ineustry has recently focussed on a problem co=.only referred to as "voltage collapse" in which the voltage decreases slowly, as comnared to a fault where voltages are affected suddenly.The ter,-Li s owly ind-ic ates a vc) I t age decay perl od maasu-l-ad in r,.- dinutss-rd --imes -Folows a -Faul-l- 'T,,h(7reaft.er Mai"ninr, Scrue- c ' rcuitz-y is unabl, e to carry ±-he ioad.,'t ot-he-r times vo Itage co! liaTDse aDpears to be caused by a gradual buildup of load -J.-, excess of a-,. 7ailable generation and power delivery cJLrcuit'_-r-y. It J_s genera-1 ly fou-nd that present art supervisory control and data acquisition (SCADA) systems provide i-n.sufficlent information to give any mozre than a. supe--f'icial explanation of the voltage collapse phe-ncmana. The A,,-"C Is hel,:., allev-at-e thils -problem by switcaing capacitors ON within one second as V01taces -10 colla-ose to a 1-init voltage generally set 5% Dclow nominal volzage.

Downsizilng of electric utilities has resulted in work burdens or), fewer personnel which, in turn, calls for nore autom.at-ed ecuJ'LDr,.e,-t- At the saria tirne competition between utililtias resulting fron z_'-e Policy Act of 1992 has lad to requ_-Lrements to carry raore i5 d1stribut-'Lo-n transformers and l-;'_nes. Agal', n. a greate,r use cf autcnaticn- is in-dicated.

-0 W4 U. S. Patent 5,422,561- issued L_ _-11-Jantsa-- a! describes a ra(_Jo I - - bu-ior. l-ne capacJtor contro-1 in trial contlro scheme c-F distrl -L C=14 Sout-hern -;_fornia. Th-Ls scheme reads voltaTes at lower vol-L-age locations and telerne-ters these readlngs, generally by zrac!Lo., to a cent--al location. At the central 'Location a 7..iathematical intodel o-F the d4 Lst-ribut-ion system is used to compute whettler o.- not each capacitor ca-n be connected or disconnected without having the voltages after switching ao cuts-Lde li-mits esta-bl--'Lshed by state statutes. This scheme has t_)e vv labor in-ensve requirement of es-abl'shina the na--hemat'cal model er- _L 4 0-oeration. Even ncra Uf.] ff cul s t'ne cor--J.nuing this mods! tl-iat- "S 'Dy the contln-jai --..ng of: lines syste-I Inas been reported in Itzhe press as having difficuit-y wiikt-'h I false operation of capac-Ltor switches as truckers -oass the capacitc-- locatio-s with their lcensee, radics i- use.

z 'k CROSS REFEREITC S TO RELATED rPPLIC;,TIONS

United States Patent No. 5,31-5,527, METHOD "-,'..D Ir-Pz-'QAr-L,US PR0VID--NG -HkLF-CYCLE DIGZITIZATION OF AC ST G-KALS BY;,S. ANALOG-TODI-I:-!T,,IZ- CCI-VERTER, issued to Robert- W. 2-eck',lk7JLth, the sane -'Inven-.o--r- -5 as in the Present application., d-scribes ap-aratus and rletliods for sensing on-'y positive half cyclas o--,': a-7t-rnating Current (-AC) igna."s.

U. S. Patent 5,544,064, kPPAR:,.rl-CS KNID 2NIETHOD FOR S.MsiPLTjZ; STGNALS SV'n-Zj:_,ICNCUS 'j-7 TH kNALOG-170-D 7 GTTA:- Co"a- 'ERTER, by Robert W. Beckwith, t-he same invent-or as -Ln the presentaDplic-t'.-':-on describes appa--rat-us and 'methods u-seful in adaptive wave synchronous with a free running analog to digital convert er (AIDIC The present in'vention ccrmbines use of half wave tachnoloc-gy u. S Patent No. 5,315,527 togetL.-her with the synchronous linear techn, - -he ojogy off U. S. Patent- No. 5,544,064 in greatly reducng hardware and software requirements and at the same t4me greatly -)erat;ng sneed of an ada-pt've T I- - ncreasing the o,, mul-iu-nc-ior.', control for use in an electric utility substation.

U. S. Patent No. 5,54-1,498, DISTRIBUTION CIRCUIT V.LR KdT_A_GEMENJT_ USING ADAPTIVE CA.PACITOIR CONTROL, issued to Robe'_rt. W. Beckwit-In-, ',-)e Jnventer herein, describes apparatus and methods of usn g T TC cont-1-ol annaratus having a VAr bias to beneficently influence the switching o-f adapt-live capacitor controls (kCC's'. This invention describes the ACC's j L_ - - ul.

and svsterm control of V.Lrs using a variable voltaue substation sou--ce h. e Use w n- -i c h -Influences t h e switch'-- ng o -f 7_CC ' s W i th 0 u t t corL-tiunIcat-ons The presen-L _JnventL"Jon fulffills the control of substa 4 CD -age as dsclosed in U. S. Patent 5,541,498 and adds vo-!L- U X _- u n C t -1 0 n 0 Z C 0 n t _70 I of' substation cappacitcrs so as to provide overall control o f an electrlic utility svstem by coordinated caDac_I_'_o__r s W I.IR_ T - E- 7 -Sy N.G "37 U. S. Patent No. 5,550,338, LOAD TAPCHI"I.NGER 7 IT LRISCN OF L,,Z).kD CURREITTS, issued zo Robert W. BeckwJth -he N COMP_ L 4nventer hereiln, describes a method of paralle-l-ina 'Load t a -D c h a n cT n a -=ansformers bv com::)a-ring ±-'.-J,.e -relative -ohase angles of pa; rs of ad-jacent, transformer load currents connected in daisv c1nain fashion a--round a - 1") - __ L. '71 - L - _' L -;.

Li-is iDatert requJres accurate comparilson of the re"atve iDhase of 6 a --eCrU4 two AC currents; ioe-,_ -n a an(f -.,..ery accurate way by the present -invention. Tnccrporation of -he daisv chain paralleling becomes an easily added function provided by nodest additions to the microprocessor.-rogram.

U. S. Patent applicatIon Serial No. 493,423, A METHOD FOR OBTAINING THE FUYDkvENT2-,-L kND ODD HAJUMONIC COMPONENTS OF AC SIGKLS, filed by Rcbe--L- W. Beckwit"h, the invente.- herein, on June 19, 1.995 describes ziethods Z"or obta-Ln--ng the funda-men't--'al com z) o n e n t and odd harmonics of a half wave AC sianal. The priInciples for current'- s and measurenent of the funda-m e n 4L--al conponent off AC- voltages are used in the 7Dresent invention.

U. S. Patent aTDplicat"ilon Serial No. _152,00I, -YTICRODCONTROLLER BASED T-APCF_kNGER EHIPLOYING HALF_-WAV, DIGIII71.ZATIONT OF AC SIGNALS, filed by Murty Yalla, Robert W. Beckwith, the inventer herain, e4L,- a! on Noverber 9, 1993 describes anDaratus for kee,)ing track of tap positions in tapciianging transfornezrs and regulators which requires sensing of AC voltage states. In certain usage the appara"Cus and 0 mehods desc-bed J.-LI Serial No. 152,001 cannot sense tapchanges by SCADA cor=unications not involving the apparatus and not changes of AC volt-age states. The Present invention inciudes different apparatus which circun.vents these problenas, and provides reliable keep track of tap positions of t-apchanging transfornme--rs.

U. S. Pat--ents No's. 5,315,527, 5,544,064, 5,541,493 and 5,530,3318 as well as applications Serial '-N'o.s 493,423 and 152,001 7 S!Tr,TY!ARY OF THE!YVEYTION A mult--Lfunczion control rela,,-, providing appa-rat-us and me-Chc::s for 4 implementing automatically adaptive switching o-E load tapchanginu transformers and -regulators, thereby decreasing the n umb e r o-L tapchanges, measuring and using VArs to bias the regulated voltage to cause adaptive capacitors controls to switch d 4 Lstribution line canaci-IL--ors, controlling the switching of substation capacitors, recording and communicating data externally.

The foregoing features and advantages of the present invention will The be apparent from the following more particular descr-iption. accompanying drawings, listed hereinbelow, are useful in explaining the invention.

BRIEF DESCRIPTIONS OF THE DRAWINGS

Fia. 1 is a drawing showing an ACC connected %to an electrical power distribut-ion circuit, together with an LTC transfo=er using the inventive control JLn a substation supplying voltage to XPICC's; Fig. 2 expands the substation portion of F 4 L -g. 1 to '4'_nclude the Controlled switching of substation ca')acitor banks; 0 4 to an ele Ctr4 - Call Fig. 3 is a drawl-ng showing an ACC connected t- power distributlon circuit, togethe-.- wilth a regulator using the in-"'entilve control in a substation su)plying voltage to ACC's; Fig. 4 is a dilagram of a system consisting of a potential device and a current transfo=er providing _Jnput-s to an LTC control, in turn having outputs to power syster. apparatus; 8 Fig. 5 -is a nore detailed diagram of a. sing"'e L chip ITC control hav-i--.-- a -"''n!P'-'t and a. cla.-r-ent transffo=er ir)-pu.--using a -3-2sistive burden; Fig. C- is a rore detailed diagram of a sJLng-1e chip LTC control having a voltage input and a current transformer input using a capacitive burden; Fig. 7 4 s a more detailed diagram of a single chip LTC control having a voltage input and a center tapped current transformer input using resistive burdens and provid4Lng two ADC inputs for measurement of the entire current signal; Fig. 8 is a dJLagram showing one cycle of AC voltage and current waves wherein the positive half cycle JLs sampled and the negative half cycle - zs suppressed and, if sampled, y-4--lds samples whose values are zero; SCr4 J- Fig. 9.4s a flow diagram de -b--'ng the SLINIII, progra.-','Uming method, useful in LTC contro.'s, for obtaining measurements of an AC wave, making computat-icns, performing tapchanges and co--rrjrunica-L.-ing to a coriputer.

network; Ficr. 10 shows voltage and current ti-me lines for raeasuring voltage an.pl-itude and combining with half wave current sLgnals using a resJLst- ive burden to obtaJLn watts and VA-rs; Fig. 11 shows voltage and current time lines for measuring voltage amplitude and combining with a half wave current signal using capacitive burdens to obtain watts and VA-rs; Fig. 12 shows voltage and current time lines for measur-ng voltage 9 amtp' ude and comb ining wi th a f u 1 'L w a v e u r r e n t- s gn a 1 u. s _J.7. c -Z L -esistive 1-is to obtai-n Watts and VArs; eT Fic. 13 illustrates a list of values of the sine of ar. angle arranged to be read in a circle divided into 12 sectors each having the same ni=,Lber of equally spaced values; Fig. 1-4 shows a first representation of AH as a funct4on_ of V - v L. L L for v between either V and VU or V and VL as useful Jrn explaining adaptive features of the present invention:

Fig. 15 shows a second representation off AH as a function oJE v - v io for v between either V and 'V77 or V and 771 as useful in explaining adaptive features of the present invention; Fig. 16 is a diagram useful in describing the inventive VAr management system wherein the substa-IC-ion voitage influences the 4 - C switching of d-L-stribution circuit IS,.

1-5 Fig. 17 contains diagrams useful in. describina the controlled switching of substation capacitor banks by the inventive control; Fig. 18 is a d-Jagram useful in explaining the comuLb-ined in-fluence on t4 or, ACC's together with switching substa capacitors using the inventive control; FLg. 19 is a one line diagram of a transmission line feeding a tapchanging transfo=er in turn feeding three distribution lines having line regulators, customer loads and ACCIs showing restricted -f-low VAr flow paths; Fig. 20 is a three line diagrar. of a transmiss-ion line feed-ing a steiD-down transformer and load tapchang-ing regulator in each phase of one distrill'ution line having line regula-L-ors, customer loads and ACIC's -'_llustrating furt.-ner restricted VAr flow paths.; F4 Ig. 21 shows automatic voltage reductLon for load management; Fia. 22 shows lengthening of the IIH?l timeout as a function of transformer load current; Fig. 23 is an isometric v-Lew of the inventive control having a two way infra-red port and using an external computer as the man-machine interface and also the addition of a wireless modem; Fig. 24 shows a test setup involving three single phase regulators; Fig. 25 shows an isolated 120/240 VAC service drop tothe ex-oerimental setup of Fig. 24; F-1g. 26 is a 24 hour plot of the output voltage of a regulator using the inventive tapchanging control techniques; Fig. 27 J',_s a 24 hour plot of the two m,_J,=Ce average values of VRQF of a reaulat-or using the inventive tapchanging control techniques.

DESCRIPTION OF IIIIHE PREFERRED EMBODIMENIL'S

A DAY OF WATTS AND VAR CONTROL in order to better understand the interrelations of the various asDects of the present invention JLs helpful to review the expected o)eration dur-Lng a typical day of a single adaptive tapchanger control (ATC) controlling a load tapchang-Lng transforner at a d--str-ihution substation feeding lines having a niuraber of capacitors switched by ACCIs spaced along the lines.

Starting at m-Ldnight, it is expected that the ATC will have raised J-1 the voltage approximatelv one volt above -the iniltial setpoin- value a,Id t- -2 -o s,,-Jzch i-s capacitor Tlne Cille ..,as J --F' uenced all bu -,-e LCC t s for -he nductive load of customer remLa-. ning CLOSED ACC correct. SuIpply transformers exciting currents and is located at the point which results in the least increase in voltage as ccrapared to other capacitor locat Lo, -,Is - The resulting VAr flow through the LTC transfc--mer is no greater than the VArs supplied by a single capacitor.

L Typically both Watts and VA_rs load builds up rapidly at about 7:0 0 ex-, this being a hot, dry day later producing a seasonal peak load io condition. The ATC sees the VAr require-ment-s ascending and being compensated by the ACC closing of capacitor switches. The VArs increase fast-er than the capacitors switch, however and the VArs reasured by the ATC increases beyond the size of a single capacitor. In response, the AT%- decreases the volta'-e approx-imately one volt to -he inizial setpoint U value. This decrease in voltage speeds the ACC response and CIIJOSES more capacitors thereby keeping the VAr -f-"cw through -he LTC t r an s f o rmne r generally less than that supplied by a Single capacitor.

At about II:C0am, -he VArs exceed the amount suDpl';_ed by a single capacitor and the ATC lowers the voltage approximately one volt below the initial setpoint value. This influences all AC(-_,'s 4C. o CLOSE the related capacitors thereby giving all available VAr support to the lines ed by the LTC transformer.

During this peak load day, however, hi S j S 4 to maintain- the VAr flow througla -.-he LTC transforne.- with-i-ri the range of ',,TArs supplied by a single capacitor. I-Phe ATC zna-intains a record of the 12 7 e ts de'ivered by -;--s and V -.31rs measured and thereby r t1ae peak Wat 7-1 trznsformar and -t'_I-ie peak Wk_rs "Ic-A7-n - k., L, L.L - cg i-arouc.-'C-11le --ra-lsf:ormer.

The ATIC a'-so maint.ains a record of I.-Ine voltage and voltage regulation q-,-, a 1 _J t y - -5 As the load builds up, the ATC reads the 'Cransformer temperature and further lowers the voltage in approximately one volt steps., thereby temporarily decreasing t1n.e Watts load. ThIs is sufficient to lim.it the transfo=.Li er te:mpe.rature.

At about 4:00 pri. a thunderstcrm occurs at abcut- the same n, tL e io Dec-_le leave factories SUppl4ed by the lines. The reduced air conditioning load together with the reduced indust-I"Lal load produces a _t4 rapid decrease in the -inductive VArs in need of corre _Lon. The r. educed load results in vcI-Laqe increases which cause some ACCIs to switch t_ --en so, "-e VIrs -hroLl-gh the transformer rapidly go capacito-s C-Ff. E, L f rom!a--.g4Lnc. to lead-J, na. In further support of the sudden chancre, -he y 4 ATC measures this sh-if t and quickly responds b -Lincreasing the voltage This Jnfluences further Z-o at,,Drcximately the init.'Lal setpoint value. L %_ -,',CC's to sw -ch the capacitors OFF where the voltage already higher that at other locations.

Because of the ra-id change in the weather, however, this Js st'll al -1 L _Fast enough and the PITC st;II sees leading V.krs 'lcw-ng through the _.L - - - _L %_ - transf ormer. The ATC responds by -increasing the voltage approximately one volt above the initial setpoint value. This now -influences enough of the caoac-l'-tors to swItch offf t-o br4ng the VA= 4low'ncr -h=u tl I - _ - - I_ - gh he transformer within the L'L.-iii ts set by the size of a single capacitor.

13 The substation voltage is naintairned at the one volt above set-Doint i A- 4- M value -4-7 urt-her influsr-cing capacilCors to swilt-ch_ OFF at locations wik..h L.1-__ highest, voltage during the evening until only one is left CLOSED as people go to bed leaving the supply transformer exciting currents to again become a factor as midnight approaches.

KnowLng that this was a peak day with a sudden charge in the weather at A time known to be critical, the next day a sys"Cem operator transfers data from this and other ATC's into Internet for study. The operator quickly finds the peak Watts and VArs. The Watts, added to Other readings gives the peak generator load. in addition the readings shows the spread of the load over the system.

Front the peak VArs the operator determines the shortage of capacitor correction and gives this information It---o the planning department for consideration of adding mcre switched poletop capacitors.

7 5 Ir ter- includes the da; ly voltage - The data obtained by In" net also profile from which the operator notes the minimum value and the rapid recoverv to the _41-n-itial setpoint value during the critical changes at 4:00pm. The quality of voltage regularklon is noted as well as the degradation in quality as required to overcome the changing conditions 2 0% during the day. 7he daily profile of Watts shows -hat the automatic U k- voltage reduction helped avoid transformer overload and averted the need W4 for a system -Lde voltage reduction.

Since the weather condition was state wide, operators throuahout the state are able to obtain data from neighboring utility substations and study the intercompany flow of power during the day.

14 THE INVENTION IN DETAIL Please refer to Figs. 1 and 3. 7hiS invention discloses inventive apparatus and methods useful in ATC's 62 for load tapchanging switches im on electric power LTC transformers 100 and regulators 15o.

Transformers 100 and regulators 150 are hereinafter referred to collectively as 'controlled devices'. Although certain differences exist in practice between controls for LTC transformers and regulators, ATC 62 will be considered herein as being usea-ble with either LTC transformers or regulators for the purpose of illustrating the present invention.

Tie operation of an adaptive capacitor control 139 (ACC) controlling pole top capacitor banks 119 on distribution lines is shown in Figs. 1 and 3. it has been found that the inventive adaptive methods of U. S. Patent 5,541,498, cited above, can not be matched bv manual operation of the controlled capacitor switches 120. This has led to use of inventive extensions of the adaptive methods in the present invention of ATC's 62 for use with controlled devices. The presenz invention reduces to a minimum the number of setuoints to be entered into the ATC's at time of installation. The present invention also eliminates the need for ongoing manual operation of tapswitches and in fact requires that such operation generally be blocked as being disruptive to optimum use of the tapswitches.

The voltage regulation quality factor, VRQF, by a controlled device is defined herein as the square root of the average of the sum of the squares of voltage deviations AE above and below a setpoint voltage ES.

is See equation 1) below.

1) VRQF \ZE'! - JIES 2)IYMI,); where 2) AE EM ES where ES is the voltage setpoint and EM is any voltage measurement.

The deviations AE are measured as often as once per AC cycle in ATC,s 62 which sense voltage only. The deviations AE are typically measured 20 times per second in the ATC,s 62 measuring both voltage and load current. The average of the squares is obtained using short term and long te= recursive equations. The short term equat-Lon has a time cons4L-Iant in the order of minutes and is useful in displaying the variations in VRQF during a day, as shown in Fig. 27. These short tern, values of V.RQF are then averaged using tinne constants preferably in the order of one week and used with counts of tanswitch operations to adaptilvely bring the number of tapswitch operations to a desired weeki-y -5 Jty o-I - Laverage per day or alternatively to br-41 ng the qual-L voltage control to a desired vaLue.

A count of cycles of the input AC voltage signals is useful as measures of time by the microprocessor procram. Descriptions of this - 4 method of L.-Inekeeping is given herei.n.under.

4 Fig. I shows a power distribut-ion substa-Lion circuit ":,roV 4 L I- -1-d-ing adaptive control of load tapchanging transformers 100 (shown for simplicity in single phase form). Transformers 100 have three phase primar-y windings 101, often at hilgher voltages of 69, 115 or 1-32 Kv, -ohase to Dhase. Transformer 100 secondaries consist of main windings 107 and tapped windings 102. Windings 102 are connected by switches 118 16 o buck or boost t'--,Le voltages of -he main wind-ngs 107.

Wizid-ings 102 have -"-.aps 113 on each of three p1nases selected three phase tapswitches 104, in turn dr 4 ven by motors M having drive counter contacts 108 closing mechanisms 105 with counter contacts 108; L. _L briefly when each tapchange _Js me-chanically committed. The motors M drive mechanism also may include contacts 142 which are movable so as to be closed only on a tap position selected as one being often used and therefore suitable for frequent- correction of a tap-change keep track procedure. Motors M are powered by single -chase transformers 103 having io primar-y 116 receiving voltages from phase 1 to neutral 143 of the voltage controlled outputs of transfo=rers 100 via secondaries 117 generally at 120 or 240 Vac. Mot-ors M may have windings 114 which, when Un 4 T powered, causes motors M to r _1_1 the direction of increasing tap Dosition and having a winding 115 which, when powered, causes motors M to run in the direction of decreasing ta-- pcs_-';-;Iio-Li. In any instance, motor direction is obtained by use of one or the other of two contact closures, R and L.

T, r ansformers 106 provide 120 Vac from secondar-y windings 141 to the ATC,s 62 in response to primary 140 connections between phase 1 and neutral 143. The ATC,s 62 provide output raise (R) contacts and lower (L) contacts which correspondingly operate motor starter relays RR and RL. Contacts 109 on the m-otor starter relay RR cause the motors YZI to move in the raise direction when the relavs RR are operated and contact on the motor starter relays RL cause the motors M to move in the lower direction when the relays RL are operated. Isolated motor starter 17 FIR co;r-t-act 11-1 cl-oses upon operation of the start-ers RIR conmectirig the 2 _i-ilar 1 A3 an' -so' ated raot-or sta-ter RL Y 0 D.- e UZ. r a c o n t a c s 11. 2 close u-,)o-,)- cneration of starters RL connecting ATC 62 binar-y -inputs LR to neutral 143. The A71C, s 62 sense closure of contacts 111, -f-ollowed bv closure of counter contacts 108 and increases the ap _OS4 record of -. _Ltion by one The ATC,s 62 further sense closure o-F contacts 112, followed by closure of counter contacts 108 and decrease the record of tap position by one. Adjustable switches 142 selectively are set "Co a t"requiently used tap position and are connected to the ATC, s 4 62 b-nary ter-minals SC. The identities of the freq-uently used tap T n-os - s are en-±ered int TC controis 62; and, ATC,s 62 correct the _L - L_ L_ L are on records of tap positions, Jf neces- azyr, each time -he tapswitches the frecnie-ntly used tap positions.

Tanswi-t-c'n knowledge is used aereinhelow to determine VP, the VArs fiowing I-n or out of an LTC -transformer primary. See discussions -refarri-ng to F - _g. 16.

Fi a. I f urther shlows typi. --a! -p-ole-top capacitor _J.Ds tallations toget'll-ler with phases 1, 2 and 3 and neutra-2- 143 conductors 0 - P 0 w er distributio:)_ lines 'Led from the power distribution substat-Jons. Phases 1 a-Lid neutral 143 conductors are shown connected ap-prcpriately to the substation circuitri. Phases 2 and 3 are not shown connected to transformers 100; tor simnlilcitv transformer 100 is re-oresented in single -hase form. ACCfs, 139 receive power from 7phase 1 through stapdown tra-ris-LI-ormers 1-38. Ncte that at other capacitor locations, transformers 138 7may alternatively be connected to phases 2 or 3. Note that ACC 139 has termnals designated N, H, 0 and C representjing Ye,_,tral, Hot, Onen and ',',lose. 'Hereimafter th.-_ e-_panded expressions for t-hese terminals; Neutral, Hot, Open and Close will be used. The state of the capac-itor switches 120 will 'Le referred to as OPEN or OPENED and CLOSE or CLOSED. Power factor correction capacitors 119are show--,I connectable through switches 120 4%.-o distribution circuits phases 1, 2 and 3. The ACCfs 139 selectively close circuit-s from the ACC 139 terminals Hot to Close to operate magneti-c devices 121, thereby closing switches 120 and connecting the capacitors 119 '11--o the distribution 0 -14 C 4 3Dowe. _nes and closes _Lrcuits from the ACC 139 terminals Hot to Open to operate magnetic devices 122, thereby opening switches 120 and disconnecting the capacitors 119 from the distribution powerlines.

e4_ Af ter the devil ces 121 have perf ormed th _L_ closing f unctions, they latch closed and contacts 124 open, re-movinc power fro.-.1 the devices 121.

fter -he devices 122 L. - f A.;- - L have perfo=ed their opening functions they latch open and contacts 123 open, removing power from the devices 122.

U. S. Patent No. 5,541,498 describes methods whe--r-e-in the aploaratus shown in Fici. 1 JLs used to control VArs flowing through transformer 100.

The present invention pro V4 -des add 4 ticnal adaptive features for ATC, s 62 to reduce the nuziber of tapswitch operations both in fUJ44'ji_g -he V.k bias reau-irentents described in U. S. Paten"'_- No. 5,541,498 and for other regulation of substation outlDut voltages where VAr bias is not used.

of Fig.

Fig. 2 e=ands the subsat-lon portion i to show -he switching o-f substation canacitor banks. Three phase bus 151, shown in 2 5 single phase form, feeds power to transformer 100. Bus 151 voltage is 19 crenerally at higher voltages of -765 to 230 kilovolts at a transraissiop substation ar-,d 11 20 to 69 I-,Ilovclts at a Istribution sta---cr-. Three -onase bus 152, shown in single phase fo=, is connected to the regulated output voltage of transformer 100 so as to feed more than one line radiating outward. Secondary lzus voltage is generally at higter transmission station and at voltages of 230 to 69 kilovolts at a intermediate voltages of 4 to 34 kilovolts at a distr-ibution L station.

The te= "wheeling of electric power" refers to the practice of electric utilities to competitively sell power to customers not directly fed by the selling utilities, transmission lines. The 1994 Energy act encourages utJL-lities to wheel power through their transmission lines.

Capacitors 169 are often used at transmission stations to supply the VArs required by the wheeling c power through transmission stations.

Prior art practice has been to switch the capacitors CLOSED and OPENI as

L 1 -1 L required to maintain the voltage level whJch other-w-se tends to lower as the result of power wheeling. Prior art LTC controls then cor-r---cted -- For the voltage increase as the capacitors 169 switched OPEN and -for the decrease -in voltage as capacitcrs 1-69 switch CLOSED. Under prior art practice, coordination of capacitor 169 switching control and LTC transfo=er control is difficult and leads to excessive LTC transfor-mer switch operations. The present inventive ATC 62 solves the problem by 4 comb-Ining the control of capacitors 169 switchJng with the control of L L.

tapswitchs 104 switching (as descr-Lbed -Ln greater detail here-inunder.) Capacitors 169 are switched OPEN by ATC 62 outputs 0 operating switches V4 160 -a sequencing apparatus 161. Capacitors 1169 are switched CLOSED by -s C operat4ng switches 160 via sequencing aDDaratus 161.

ATIC 6 2 output aC4 Cap _Ltor banks at transmission substations generally he.ve mor than one section of capacitors 169 which are sequentially switched OPEN and CLOSED by successive operations of ATC 62 output contacts Open and Close. Often feedback contacts 165 are provided to ATC 62 which are closed when all capacitor 169 sections are CLOSED. In addition, feedback contacts 164 are lDrovided to ATC 62 which are closed when all capacitor 169 sections are OPEN. A capacitor section sequenc-Ing apparatus 1-61, as known in the art, is utilized.

The combined control of tapswitch 104 and distribution substation bank capacitors 169 is accomplished by ATC 62 in the same way as described above for transmission substations. Selectivelv ATC 62 also provides the inventive raising and lowering of substat-ion output voltages to influence ACC switching of capac,;Ltors 119 J-ocated on distribution lines fed bv the distribution substation. The joint control of t-apswitches 104, substation capacitors 169 and distribution line capacitors 119 by ATC's 62 is described in greater detail hereinunder.

Fig. 3 shows a power distribution substation circuit providing ATC 62 of regulators 150. Note that one regulator 150 is shown in detail regulating voltage Ein to phase 1 of distribution powerlines with two additional regulators 150 shown in abbreviated form, regulating voltages on phases 2 and 3 of the distribution powerl-ines. Regulator 150 has an input voltage Ein, typically 7800 VAC phase to ground, with the output regulated upwards and' downwards by single phase tapswitEch 104.

21 Reg-ulators are generally used in sets of three, one per phase, cand each wit-IL separate ATC's 62, as shown in Fig. 3. These may be applied 1-0 the output of a distribution substation feeding each of several three phase distribution feeders or may be placed midway on long feeders to reregulate the three phase voltages beyond that point. Tapswitches 104 are driven by motors M having drive mechanisms 105 with counter contacts 108; counter contacts 108 closing briefly when each tapchange is mechanically committed. Motors M drive mechanisms further have contacts 142 closed only on a neutral tap position where the voltage Ein is equal to the phase voltage leaving the regulator. Motors M are powered by eiV4 single phase transformers!03 having primaries 116 rec ng voltages from phase to neutral 143 of the voltage controlled output of regulators via secondary 117 generally at IL20 Vac. Motors M may have windings ii,, which, when powered, cause motors M to run in the direction of 1 5 J ncreasing tap positions and having windings 115 which, when powered, cause motors M JL--o run in the direction of decreasing tap position. Tn any instance, motor direction _Js obtained by use of one or the other of two contact closures, R and L. Trans -formers 106 provides 120 Vac from secondary wIndings 141 to the LTC ATC 62 in response to prinarry 140 connections between phase 1 and neutral 143. The ATC's 62 provide cutpu-IC raise (IR) contact and lower (L) contact which corresponding lly operate rqotors M. Transformners IL06 are often included in regulators 150.

Fig. 3 further shows a ±yp4ca' pole-top capacitor installation of ACCIs 139 together with phases 1, 2, 3 and neutral conductors of power 22 distrilbution lines fed from the power distribut-Lon substations. Neutral nected to the substation -r-und circuitry. conductors are s-o-,,Tn cc--iL Phases 1, 2 and 3 are shown connected to regulators 150. ACC's 139, as shown, receive power from phase I through stepdown transformers 138.

Note tt h a "C. at other capacitor locations, transfo=iers 138 may alternatively be connected to phase 2 or phase 3, however it is general practice to switch all three phase capacitors with a S4 ngle ACC sensing one of three phases.

Power factor correction capacitors 119 are shown connectable through switches 1-20 to d 4 stribution circuits phases 1, 2 and 3. The ACC 139 selectively closes circuits from the ACC 139 terminal Hot,'_ (H) to close (C) to operate magnetic devices part one 121 thereby closing switches 120 and connecting capac-itors 119 to the distribution -Dowerlines. Selectively the ACC's 139 close circuits -from the ACC 139 'Cerm, inals H to 0 to operate magnetic devices part. two 122 thereby opening switches 120 and disconnecting the capacitors 119 from the distribution powerlines.

After devices 121 have performed their closing -function, they latch closed with contacts 123 and contacts 124 open, removing power from the devices 121. After devices 122 have performed their opening -function, they latch open and contact-s 123 open, removing power from the devices 122. ACC's close contacts Close and open for sufficient time -for the latching to occur.

Fig. 4 illustrates ATC 62 having self-contained microprocessor 1 including central processor unit (CPU) 7 with on board memories 4, 5, 23 and 5,see Figs. 5, 6 and 7) and also including an analog to digital converter (ADC) 2. Note that the use of on board memories is for descriptive purposes only; the memories may selectively be separate chips. "Power supply 18 obtains inputs from potential device 14 and supply power to microprocessor 1. CPU 7 provides outputs to operate relay 17, which is connected to controlled devices. Potential devices 14 also provide input voltages for the ADC's 2 for the purpose of digitizing alternating current (AC) voltage signals from devices i4. Current transformers V furnish input current signals to ADC's 2 fro--I.

io one phase of the AC circuits. The current inputs to ADC's 2 are for the purpose of digitizing AC current signals.

All other parts of Fig. 2 are described hereinabove in relation to Fig. 1.

The present invention includes a program used by microprocessor i i5 for the multiple functions described herein. Fig. 5 is a more detailed circuit diagram of ATC's 62 using single chip microprocessors i containing ADC 2; in turn having protective diode!D!, and having the ROM 4 containing programs, RAM 5 and EEPROM 6 memories; further having CPU's 7 and ports B and C 10 respectively driving raise output contacts R and lower output contact L. External crystal 9 and self contained oscillator 8 provide clock frequencies for the microprocessors 1.,,nalog to digital control logic (ADCTL) 12 controls flow of digital samples from ADC 2 to ADC registers R1, R2, R3, and R4 collectively numbered!I. Power supplies!8 supply +5V for the VDD supplies as well as the high ADC references VRH of microprocessors 1 and also neutral 24 returns for VSS and lo-,,,, ?.DC referen-ce of nticroprocessors 1. T.ne i- ,Inu,-- I voltages are reduced by resistors R70 and R71 to signal E connect L - -e-d to inDuts AO of A-DC 2. AC currents I from current transformer 16 (see F- Lg 4) flow through transformers T2 having secondaries TSI feeding -ors R78- Voltages across R78 are dJvided by current to burden esist resistors R72 and R73 so as to yield current signals!I in turn connected to inputs Al of the ADC 2. Diolde D70 and D71 provide overvoltage protection for ADC inputs AO and Al. The circuits of Fig. 5 prOV4 des half wave dig2tization of the voltage signals E and current L. -L - - I'L - signals I! -In accordance with referenced patent No. 5,315,527. Fig. 5 4 illustrates use of resistJLve burden 78 providing a positive half wave signal I! to ADC - Lnou, Al. Use of resistive b,=-dens R78 provides sjgr.alS TI which a-re -r phase with signals E.

Fig. 6 is ident,Lcal to Fig. 5 with the exception of the re-p-lacement -1-5 of resistive burdens R78 of Fig. 5 with capacitive burdens C! of Fig. 6.

T'l-le voltage across C1 due to current I is 900 leading with respect to Vojage 4 signal E. T,he.1-s divided by resistors R72 and R73 as in the circuit of Fig. 5 forrming signal!I. Use of caDac-itive burden C1 on current transfo=.,er T'-- gives 6 decibels per octave attenuation of current signal ha=,,onics so as to more nearly respond to the fundamental component of the current signal when desired. Other conponents shown in F-;:_g. 6 function as described above in relation to Fig. 5.

Fig. 7 is also identical to Fig. 5 except that voltages across 4 windir-g TS! are dv-Lded by resistors R74 and R75 forming signals III in phase oppos41-tion to signals 11. Signals III are protected from o-vervo-l'-tages by 6-Jode D72 and to ALC]Lnputs 2.2 thereby prcvidinq -; =or ane. vs s o if both po 1 arit" i es o f curre rt T Fig. 8 s"LLmm-,arizes the sarpling of the pcsit-Lve half cycle, a, Of AC current and voltage waves 195 as described in referenced U. S. Patent No. 5,315,527. Positive half cycles of wave 195 are sampled by ALDC 2 and samples 196 are output to CPU 7 of microprocessors I (Fig. 5, 6 and 7. iqegative half cycles, a', of wave 195 are suppressed by TD11s nrotect AJDC 2 and any ADC samples taiklen during these periods are zero.

Vae half wave teclimology of U. S. Patent No. 5,311.5,527 and ---.he synchronous programming (STTM) technology of U. S. Pat-ent No. 5,544,064 are ut-L.I.-Lzed in the present invention to obtain the benefits of the in.proved resolut-ions of signals E, Il and I!'; the reductions in -he resultant Jrprovements 4._T1 reliability and cort-oonent's needed; and, L. L. L. _L - the re6uctions in cost. Fig. 9 summa--rizes the SLIM technolog,- showing that subprograi,-, 41 takes samples from A-DC 2 (Figs. 5, 6 and 7 herein) in svnchrcn_is.-,n with a free-runnJLng rate of: signal conversions by A_DC 2.

When not ta'King samples, preferably during negative half cycles o-f input AC signals, the progra--ni progresses linearly (one task at a t_me) via paths 45, 46, 47 and 48, as required for computation by subprogram 42, C) to ccninunicate via subprogram, 44 and to control tapchang-ing and C4 capa _Ltor switches via subprogram 43.

Use of the SL7M technology is preferred since it makes possible -he use of ruc7aed, although relatively slow, TP.JLcroprocessors as used in the aut-omotive industry. The SLIM technology results in programs that a I- e 215 ve--?-y short so that even at microprocessor clock speeds in the order of 26 e are o:.D±- ned due L jahertz, 240 sa-mp! es per half uvc to the -1a __ - L r a-m e vely quick running t-Ine of the short prograzms. The ent' re prog- 4 the..riventive 2.TC's requires from 5000 to 10,000 bytes of RO4 for storage. The prograr, loops run cont 4 nuously withou-C. interrupts and each loop lases but a portion ofa the total program, at a ti-me.

The various features of this invention utilize the program, described herein. Comparable programis using prior art. technology may require 10 to 20 ti-nes the memory space and run 10 to 20 tiries slcwer in terms of clock cycles. it is to be understood other microprocessors and larger programs, are useahjle to obtain the inventive apparatus and methods described hereinbelow. However, the technologies d-J'sclosed in U. S. Patent-s 5,31CZ,527 and 5,544,046 are preferred a7--d are -Lsed hereinbelow in describing the invention.

J:Z MEASUREMENT Figs. 10, 11 and 12 show the measurement- of the JLE-Lirdamentai coimponents of voltage signal E during one half cycle designated as time iDeriod EI, the measurement of the real (P) component of a cul:-rent signal ii during the next full cycle designated as time period ?I, the measurement of the quadrature (Q) component of the same current signal ii during a succeeding full cycle designated as ti-me per-Jod Q1, with a final half cycle designated as ti-me period CALCULATE COMMUNICATE SEEEK ZNZ for coimputation, co.Tmmun i cations, and resynchronizing with the next zero to non-zero (znz) transition of voltage signals E. The programs runs synchronously with t'--)-e A-DC's from the initilal znz detacticn of, 27 4 volt-age s-gnals E to the end of 2 cycles. The only instru, ct ion 4 recrul-ired from. the program to the ADC 'is to change from, signal z -0 signal i at the end of time period -E-E'-->. These measurements and the tire slot for cormikunicat ions occur at the rate of 20 per second for a 60 Hz power frequency.

The expected values of P range from a positive maximum to a negative maximum. Negative values indicate a reversal of power f low and is useful in reversing the operation of ATC's 62 should there be a reversal of power flow as sometimes occurs when regulators are used at io midpoints of d1stribution lines alternatively fed from either of two points The possible values of Q also range from a - 'tVe DOS-,,aX4r,,un, to a - _L -.4- L_ negative maxiMiLm. At a distribution substation, negative values indicate an excess of caDac-itive correction of inductive loads.

Computed values of power factor from P and Q obtained using the inventive measurement described herein are found to be an order of m - L_ h agni tude more accurate than obtained by present tec 'nology method using 15 samples per cycle.

A second current not shown can be added and alternatively switched in place of current Ti. This provides measures of real, P, and reactive, Q, power from t1ne second current. For example, P and Q can be used to obtain -he phase relation between the current and voltage E as a reference.

P and Q determinations from two currents may be processed to establish -he relative -ohase relation between the two currents as 28 4n referenced U. S.

requIred for the daJLsy Chai paralleling disc'osed P a t _- n 5 f 5 3 0, 3 3 8 most conveniently, the r=--o P/Q s cornputed u-,zing a first current is compared to the ra--o p/Q computed using a second current. The algebraic sign of the difference in -It--he two ratics -ion of wh;ch current 'eads the other in phase relation to is an ind-icaL_ L_ the conimon voltage E. When the ratios are equal, the two currents are pa4 in phase with each other. When all _rs of currents are in phase a-round a ring of transformers operating in parallel, as indicated by equalit-y of P/Q ratios, the paralleled transfornners are operating with io minimal losses introduced by paralleling as disclosed in greater detail in reference U. S. Patent No. 5.530,338. The equalitv of P/Q ratios as the indication of most efficient operat-Lng point- is generally true with secondaries of the transfo=ers in -Parallel even though the pr-imar'Les are not.

3 Ncte that imeasurements related to each of two currents are available at the rate of 10 3Der second by programs alternating between the two currents. The comnunications t-inne windows, however, are provided after each current measurement and therefore at the rate of 20 per second for a 60 Hz z-,'.C frequency. Note that with either one or two 0 currents, extended per-Lods of time can be meas-dred by JLncrament-ing a count during each of 20 computation times per second, providing a tire 4 op U _S of the ATC Is measurement resolu- 'on of three AC cycl es. ir ap-ol i ca where only voltage need be measured once per cycle, cycles may be counted giving a tJLming resolution of one AC cycl e.

In the follow-Lng discussion of Figs. 10, 1! and 12, the voltage 29 wave E is shown only in the firs ha" cycl e of tire 7,,.7hpre its aniolitude s rie asu red. Current waves are s' own n -he next t-,,70 fu' 3 CVCles of time where P and Q are measured. values fron the circular table of Fig.

J-3 are shown along time line marked fol by lines fcllowng the profile of values as they are used in measuring P and Q as described in greater detail hereinunder.

Fi--s. 10, 11 and 12 illustrate three var-ations of an inventive L L.

method of directly measuring Watts and VArs without the conventional -F a vol-age, the amPI4-ude o-r necessitv of measuring the am,,Dlitude o- L current and the phase angle rel-ation between them and then using trigononetrIc computations to calculate Watts and '\Tkrs. Fias. 1-0, 11 arid 12 relate to c3_rcu.Lts of Fias. 5, 6, and 7 respectively. By connecting an AC voltage and current to an A_DC as sh-own in F-41glTs. 10 ancd 1-1 only the positive half cycle cf each signal- is sa-m-pled by th, e kDC in accordance with reference U. S. Patent No. 5,315,527. T17ie a,-n.D'L i t u d e o -f the -Fundamental component of s,'Lanal E is measured by first -,'--'nd-ng the zero:non-zero (znz) tran S4 "jop indication of the start of a Dositive half cycle of silgnal E. The measureiment _Js accomplished in one half cycle time (marked <-E'--> on Figs. 10, 11 and 1-2) recognizIng that due to the expected ol even har-monics of the voltage signal, the negative half cycle -is a m il rror image of" the iDosi- tive half cyc1e and therefc--re contains no additional info=at_cn to th-at obtained in measurina the iDositive half cycle.

Fig. 12 illustrates inventive methods of directly measuring Watts 2_ 3 and VArs using the circuitry shown in Fig. 7 with the variation ofE D -0 d 1 s n a n YD'hase current i and signal 1!' 1800 ou- O-P phase with current I. By connecting an AC voltage and these current signals to an A.DC as shcWn 4 Ln Fig. 7, the full wave of the current is sa.rzipled as shown in Fig. 12. Use of resistive burdens R78 provide measure.ments responding to current signals including all harmonjLc components when required.

BV switching from one half cycle to the other (from ADC inputs Al to A2; see Fig. /) and using timing obtained by a previous sampling of _1tage E positive half cycle, the entire current wave of both a vo 1. polarities of current is analyzed.

Use is made of the ring of SN values of the sine function shown in Fig. '3. Using a Dreferred factor S = 12, the ring is sho-wn divided i7-to twelve 300 sections having N equally spaced values each section.

These are divid 4 ng points ge,-nerallly selected as desirable to ef fect -PIL-Lase shifts of the sine function relative to signal E as a phase reference. Such Phase shifts are required to compensate for placement 4 O-L pozential devices for obtaining voltage signals and current trans-Ecrmers used for obtaining current signals. when used on a three phase system such placement may create the need to correct for a fixed C phase shift generally falling in 300 increments. An advantage of use of S-0.0r)j.L g p04 the table with selecta-ble star-L-Lng and I nts is that no distortions or errors are caused by the correction o-.;' phase angles as offften occu.-s in prior art analog means for such correction.

Note that any starting and stopping points located half way around the circle from each other provide a half wave function; when starting 31 at any 300 -,,o.int and -oi ul Ij -rig comple around the circ e provi des a wave. f-unction; and o,,hen starting at- e.-2,y 30^- point -,and CC) 4 ng twice around the circle provides a two cvcle function.

By using the methods of referenced U. S. Patent No. 5,544,064, a i-arge nuj7qber of samples, preferably 240t may be taken during positive portions of signals sampled. This number of samples Der half cycle will be used hereinunder in illustrating the principles of this invention.

The nu--,nber of values i-,,-i the circle corresponds to the expected number of sarriples of 60 Hz AC signals, that is 480 values for the complete circle full cycle of any signa' sa-rip'ed.

0 corresponding to a L -I - I Note that the nu-r,ibe-.s of samples per cycle and matching values of the table for use on 4 C a 50 H.z elect-r-1power system Pay differ fror. the numbbers used at 60 Hz. To properLy provide the 300 sections it is --riecessary that t'he T - 4- - 'ble by 12. The case of the iumber of values Jn the ring be divis--- ives N 40 values -5 exa-r..iple used of -match-Lng 240 samples in a ha" cycle g per 300 segment.

The -.--Lng table wit'l,. entry and exit points at every 300 is entered into ROM memory 4 of the microprocessor 1 (see Figs. 5, 6 and 7) and values are -read in a counter clockwise direction starting at a first selected point a.-nd ending at second selected point around the ring as reau-ired by anv comT)ut-ation. By "starting at any selected 300 poinl, ::11, hat the 'irst value o-F the -able read is he next one falling one means L. L_ L - - - counterclockwise arcund the ring IL r c r. -the selected point. By "ending at any selected 300 poin-;C-11, one means that the last value read is the one just clockwise around the ring from, the selected pcint.

32 Note that skilled programners can generate the ring. Zrom a snialler 4 table by using known program rninJLmization technology. The Mventive concepts are best described herein, however, by assuming existence of a complete ring of values of the sine function.

It is well known that most measured cycles of voltage delivered to users of electric power in the United States will have a distortion of one percent or less. in addition, the voltage output from a controlled device is exPected to be essentially at the voltage setpoint value. In light of these observations, values from the ring of sine functions are io used in place of actual voltage samples in the inventive process off mT easuring P and Q. on the other hand, it is known that current signals may have 'Large amounts of harmonic distortion sormetimes causina more than the expected f the signals. However it is --urther well T L. -I - - iu.m.ber of zero crossings o 1-5 -n that currenl- signals at the output of power transformers are - know unlikely to have signi-icant amounts of even harmonic components. I n general, therefore, only the positive half wave of curren-L signals are used for non-zero samples in the inventive measurement of P and Q. (An inventive process for using both half waves of current signals is given 0 for exceptional cases where both even and odd harmonics are expected in current waves.) It is further recognized that the accuracies required in measuring VArs for controlling the switching of power factor correcting capacitors is not great since capacitors are either connected or not connected.

L_ This further justifies use of inventive measurement and computation 33 a4" --echr---'Lc,rues th. may have small theoreticai errors.

s -ecessa"Ir, to measure the funda-mental components of voltages accuratelv, however, since voltages are used as the means of direct communications between ATC's and ACCIS.In both ATCfs and ACC's the -C 4 fundamental component of voltage s-g-nals are used as being unaffected by ha=onics and the changing distrIbution of ha=onic components of voltages as capacitors are switched.

During periods <-E'---> of Figs. 10, 11 and 12, the znz transition of sicmal E is first detected. Thereafter products of 240 samples of signal E and 240 values from the ring starting at 0/3600 and ending at 4 v 'I to 8011 are sumnued forning a alue proportional t the fundamental component of signal E.

Th'e computation of E is stopped aftez- 240 multiplications whether cr not a non-zero [to zero (nzz) transit-ion occurs in the voltage wave E. The 7measurement is.--ext switched f--om measuring the -L'undamental component of voltage to measuring the power (P) co-m-;Donent of controlled Unit Output.

Tn Fig. 10 it is assumed that transform, er T2 of Fig. 5 has a resistive burden R78 and it therefore is assumed thalE the real (P) S 4 0 comiDonent of current _Ln phase wJLth voltage signal E. Also since s known that voltage signal E is being regulated by the ATC 62 to rather close tolerances, an approximation oil the real (P) and quadratu7e (Q) components of power are made by Jnventively using the Fig. 13 ring of sine functions in lieu of actual samples of voltage signal E.

+_ 4 Therefore during -,T.e period <-P,--> samples of signal I are 34 mu _iP 1 -ied by 480 values from th;e rilng start-ing at 1800 and endi- ng:at and sunumed forming a value approxiniating the P comiponent of output from the controlled device.

Duiediately after obtaining the approximate value of P and during time period E-Q'-> samples of signal I are multiplied by 480 values from the ring starting at 900 and ending at 2700 and su=ed fo=ing a value approxi-nating the Q component-- of output from the controlled device.

For greater accuracy, during the <-CALCULATE COITTIUNICATE SEEK ZNZ-3 period, the values of P and Q may be corrected for the amount. the previous -nieasure of the fundamental cori-ponent of signal E departed from its, expected value. Ths is done by multiplying -he neasured values of P and Q by the ratio of the jDrevicus measurement of the voltage a-raplitude by --he voltage control- set-poiTnt.

In F 41 cr. 10 the current signals I are ass,=,.ed to be severe'v S distorted and having extraneous zero crossings. Note that durinq the fc=.L,._ing of suns for P and Q that approximately one half of the products are zero. This represents the portions of the save of signal I where due to the assumed symmetry of signal i having, only odd harmonic components, no information as to the value of P and Q is lost. For example, portion b giving only zero increments to the value of- _P and Q is the milrror image of portion b, where true increnents are obtained.

7 i-jikewise portions c imirror c' and portions a mirror a,.

F-Ja 11 is s-im-ilar to Fig. 10 except that a capacitor is used as theburden for current transformer T2. The starting point on the ring is displaced by 900 to compensate for the phase displacement wher. using a capac"tive burden C1 as shown in FiCT.

I I- - 6. The starting points for con-Dut-ations of Q are always off'set by 900 froin.l t1ne starting point s selected for computations of P.

The measurements of E, P and Q are performed the same as described under Fig. 10 above. Note that in this example, however, that the current wave I is essentially a sine wave due to the 6 decibels per octave attenuation JLn harmonics provided by the use of capacitive burden C1.

Fig. 12 shows the measurement of full waves of current wave I/!, as Drovided by the circuit of Fig. 7. The program alternates between A.DC =pul:--s Al and A2 upon detection of a zer-o s_zmple in either input. Due to the use of resistor burdens R78, it is assumed that -he real (P) component or current is in phase with voltage signal E. Dur-Ling time period <-P, > samDles of signal I/T1 are multiplied by 4SO values from the L j::; ring starting at 1800 and ending at IL800 and su=-ed forming a value approximating the P component of out-out.from the controlled device. As shown in Fig. 12, the values of the ring are shifted 900 by starting at 900 and ending at 900 for use in measuring Q.

COMPUTATION As described,"I"n referenced U. S. Patenz No. 5,541,41-98, Fig. 14 to '10 starting with 1 at shows the assignment of integer values from L. L. - the upper edge of half deadband DB and ending at an upper voltage limit VU. Fig. 14 also shows the assignment of integer values from I to 10 starting with I at the lower edge of the de-adband DB and ending at a 36 limit VL. -ical scale shows the squares of these -ower voltage The ver, li are used to 2ncreraent a t4- n,-egers whic', 7ariable H upward hV an amount AH following each measurement v of voltage signal E (see Fig.

15) whenever v is between the absolute low voltage limit VILI and the bottom of deadband DB (see Fig. 15) and when a raise in taD Position may be required should timing variable H accumulate to greater than HI, an adaptive time-out limit as described hereinunder. Fig. 14 also shows the use of squares of int-egers to increment timing variable H upward by an ar.ount AH -following each measurement of voltage signal v whenever v is between the upper voltage 1-imit V-U- and the top of deadband DB, when - 4 a lower of tap position may be required should L--Lming variable H - he accumulate to greater than HI Note that the voltage ranges betweeft t edges of band B and the linits VL and -VF. need nolk- be equal. These ranges are referred to herein as "non-!_-;Lnear ranges".

i5 Fig. 14 shows voltages between half deadband DB and either VU or 4gital VL. As is necessary in any dj- - process, this voltage range, which is fundanentally analog in nature, is d 4 vided into discrete increments. For clarity Fig. 14 shows the voltage ranges divided into 1.0 -increments with corresponding values of AH shown ranging from 1- to 100. This number of increnents of AH is arbitrary, however, and generally will be much larger than 10, say 100, and is given bv the term 1--i-I in the equation:

AH m X/Y where:

X v (V - DB) and denominator Y = V-0 - (V +;DB) when voltage v is above the deadband DB, and 37 X = (V - -DB) - v and denominator Y = (V -;jDB) VL when voltage v is below the deadband DB, where V is the voltage at the center of band DB and v is any measured voltage E (see Figs. 10, 11, and 12).

In order to reduce the size of a microprocessor program using these equations, it is desirable to avoid floating po--'Int mathematics and use only integral numbers. Note that X/Y will range from 0 to 1 in value.

Since integer numbers are rounded down to the next lower integer, the integer value of X/Y will be zero except at the limit value where An X/Y = 1. For this reason the product m X is computed first.

examination of the function m X/Y so calculated shows that either m or Y will determine the number of integer values obtained for AH, depending on which is the snaller, m or Y.

Now X and Y are obtained from values of voltage from.a measurement process. The measurement described herein and --"n referenced patents and patent applications provides a typical resolution for Y of 27100 discrete integer values. With a choice of n = 100, n will there-fore determine the resolution of the graph of Fig. 14 into 100 bars for most positions of v between V'Lj and VU. only where v is very close to either VL or VU 4 S will the number of bars be determined by a value of Y which smaller than -m.

Thus an integer, preferably starting with 1, is assigned to each increment, nrogressing from the bandedges to VL or VU. Whenever the voltage, v, is measured within a nonlinear range. Timing variable H is incremented upward by the square, AH, of the integer number of the 38 increment.

Ihis invention is not limited to the use of" the s7uare relation betwec-n AH and the increment number. A second choice is the cube or another power, not necessarily an integral power. A third choice is to double AH in each progression upward in the number of the 4 _Lncrement, A fourth choice is to have a table of values Of AH c1hosen with no particular mathematical relation to -the number of the increment. The 4 invention is not limited to these choices.

Whenever the measured voltage, v, is within the deadband DB, t-Lming io variable H is decremented by a selected amount per calculation period.

The inventive process improves its speed of response to volt a g e deviations non-linearly as the deviations approach operating 11 1 r. _J t. S. T n contrast to the invention, prior art controls generally have a flzed time response to voltages outside of a deadband.

Tn other embodiments of the inventive ATC 62, AC current inputs to the ATC are required along with related measurements of the currents and a voltage.

As illustrated by Fig. 15,. a timing variable H increments by AH after each voltage v measurement computed as the square of the integer assigned to the voltage Av deviat-Lon from the top of the deadhand DB zo the upper voltage limit VU or whenever the voltage v measurement is between the bottom of the deadband DB and the lower voltage limit VT-. Timing variable H decrements whenever the voltage v measurement is within the deadband DB but timing variable H never decrements below zero. Timing variable H resets to zero whenever the voltage v passes 39 through the deadband DB and after out-put raise (R) and output lower (-I) operations. Whenever time-oult occurs by H III the ATLC 62 -issues a raise command (R) if -,-.he t4me out occurs for voltages v below tile deadband DB and e. lower command (L) if the time out occurs for voltages v above the deadband DB.

The inventive ATC 62 is capable of maintaining a given quality of voltage regulation with less switch operations than prior art LTC controls. Conversely, using the same average rate of tapswitch changes, the inventive ATC 62 4 S capable of better voltage regulation than prior art controls.

The time out limit HI adapts daily to a value producing a desired balance between the rate of tapswitch operations and the voltage regulation quality factor (VRQF). This desired balance is selectively accomplished in one off three ways:

a) a voltage regulation quality factor VRQF is chosen to satisfy user reauirements, such as to meet state statutes limiting voltage varia-C.Lon. The VRQF 'Ls then input to the ATC and the resultant rate of tapchanges is accepted as an operating requirement.

b) a desired daily number of tapchanges as averaged with a time constant of one week is input to the ATC and the VRQF accented as adequate.

C) by considering the cost, T$, of tapswitch operations, by considering the cost, R$, of poor quality of voltage regulation and by then minimizing the total cost.

Note thatE several volts are often allowed between the voltage .1.1easured at a ATC location and the lower statute voltage li,-Iit _L L_L (generally 114 VAC) 'o take into cons'deratJon the voltage drop between the electric utility distribution lines and the actual customer loads.

The ATC's digitally increments timers, H, as the square AH of deviations Av of sensed controlled device output voltage outside of a deadband DB. The timer, H, is decremented linearly whenever the regulated device output voltage is within the deadband DB. Timing variable H is reset to ze-ro and 'IC-he control function changed from raise (R) to lower (L) as appropriate whenever the sensed voltage passes entirely through the deadband DB. A 1--apchange is made when the value of timing variable H reaches or exceeds H' Limit H' is adaptively set higher or lower, preferably once per day, so as to produce the selected one of the aforementioned balances. With a), equal VRQF, as the cho.'ce the ATC has been found to reduce the average rate of tapchanges by a factor of 40% as compared to prio-'r art tapchanger controls. See the test results given at the end of t-his docu-ment. This extends the t 4 opera Ang life of the switches thereby decreasing the number of times transformers and regulators must be taken out of service for maintenance.

SYSTEM VAR M-kNAGEMENT Using both the controlled voltage and the load current as inputs, the ATC's directly measure the regulated output Watt-s (P) and V-P%r (Q) components. The ATC's then lower the voltages as necessary when used at a distribution substation to induce ACCIs, to switch CLOSED to provide a 41 J lagg4ng reduction in the VA_-s out o-I' the cont-rclled device. The ATCs also raise the voltage as necessary to induce ACC's to switch OFF so as to provide an increase in lagging VArs out of the controlled device.

The net effect of this action is to automatically maintain the vArs passing through the controlled device within an established VAr deadband. These inventive means and methods are described in greater detail hereinbelow.

As revealed in above referenced U. S. Patent No. 5,541,498 an LTC transformer voltage is biased upward to influence distribution io capacitors to switch OPEN at locations where the voltage -is the highest and biased down to influence the capacitors to switch CLOSE-D at locations where the voltage is the lowest. This desirable effect is obtained without the requirement JL-or external commun 4 -,cations t-In-rough --he interaction of ATCIs disclosed herein at distribution subs-La--.'cns and the use of ACC's disclosed in referenced U. S. Patent No. 5,541,498 on dist-r-J.'o-ution lines supplied by the substation. The followIng describes the further inventive methods by which ATC,s provide the trans-ffo=er voltage bias and includes the switching by the ATC's of, additio-nai capacitor banks located on the low voltage output of LTC transforme-rs at distribution substatIons. The ATCIs also provide coordinated control of SS4 tapswitches and capacitor banks at transri -,on substations. The s, abstation capacitor banks may consist of several individually switched sections of power factor correcting capacitors.

42 I' N7 7 T L7NE CkPACIT,,-.,R SWIT HING TO CONTROT. STA TO!.- V RS -,.LUENCT--NIG rr, - N k Please refer again to Fig. 11 showing a. sing'e distribution line canacitor bank 11-laving control 139 and an LTC transformer having ATC 62.

Fig. I is useful in Illustrating tl,,Le use of a voltage bias in ATC 62 as influenced by the VAr flow out of transformiter 150 as measured by ATC 62.

F,I.g. 16 has a horizontal axis of transformer 100 secondary voltages or, which ATC 62 voltage setpoints are shown. The initial ATC voltage control band center is ES as shown in Fig. 16 and having a band width DB along the horizontal voltage axis. Assume deadband DB is fixed at one -,0 volt AC. The ver ical axis is the capacit4ve VAr flow measured as either going into trans forimers 100 secondaries 107 (above line Vs) or leaving the transformers 100 prirna,-y 101 (abcve line Vp). The VAr flow S a function of the auto-matic connection and disconnec-ion of capacitors 119 by switches 1-20 (Fig. 1) as controlled bv ACCIs 139.

Transformer 100 seconda.-y voltages are used as first VAr references VS and transformer 107 primar-y voltages used as second VAr references VP. V7,r reference VO I's the average of VP and VS is used in determining actions by ATC's to sw--"tch capacitors so as to control VAr flows through transfo=ers 100.

4 L L_ Voltage ES is the initial AI_TCIs 6" voltage set-point. Th4s se--ro'-t moves automatically down to voltage ES - 1 and up to voltage ES + 1 to effect switching of distribution capacitors 11-9 as described in great-ar dietail hereinunder. The deadband around any setpo-int voltage position is - DB and is assumed to be one volt hereinunder. This must be set higher when using LTC transformers with greater than one volt maximun, change per step of the tapswitch.

Deadband area A of Fig. 16 is bound by DB in width, and verticaiLly on the bottom by the size of the largest switchable distribution line capacitor 119 in VArs plotted downward from VC. Areas below VO also represents lagging VArs 1--lowing out of transformer 107 secondaries.

When the measured VArs leaves area A at the bottom (with an adaptive time delay), open capacitors 119 (if any), located at some point on the distribution system having the lowest voltage, switch CLOSED after an adaptive time delay in the ACC controlling such switciing, improving the L_ t age VAr flow by the actual VArs produced by the switching. As the vollalong the distribution lines decreases further, more capacitors 119 switch CLOSED. This has the effect of improving the voltage regulation at the capacitor locations and reducing the VAr flow through the transformer.

i5 When the distribution circuit load builds up --Faster than capacitors 119 close, the VAr load may extend below line VC. The area below line VC is divided into quanta j.Z of VArs (convenient to integer math) preferably by approximately 1/8 of the VAr deadband from VO to VC (equal to ti,-e size of the largest distribution line capacitor). A sun, Z is 2. m Z exceeds Z', an adaptive tire out limit formed of AZ When this su as explained below, the ATC 62 automatically changes thevoltage setpoint downward by DB herein assumed to be one volt, to ES -1 entering area B. Z I adapts to a value that produces a desired daily average number of transitions between areas A, B and C. Generally one expects one transition to area B in the morning and one to area C in the evening. Weather and other condit-icns ray change this from day to day, however. Therefore Z' is varied, say 10% each day, in the direction to bring a weekly average of daily transitions to a desired setpoint. The adaptive daily adjustment is very similar to the adaption of HI to obtain either a desired VRQF or selectively to obtain a desired daily number of tapchange operations.

The slum Z is reset to zero when the measured VArs go above line vC. and also after each change of the voltage setpoint in going between areas A, B and C.

-'0 The previously described adaptive fea ures oE the voltage control will then operate 44--apswitches 104 to bring the voltage within area B. operation remains in area B until the measured VArs move above line VC for an adaptive period. The area above Vo is also divided into quanta Az computed as described above. A s-= Z is --Formed of LZ2. When this sum Z exceeds Z', the ATC 62 automatically changes the voltage setpoint. upward by DB herein assumed to be one volt, to ES reentering area A. in a S4 _J_ mil lar way, when the measured VArs go above line VO from area A the voltage setpoint increases to ES + 1 entering area C.

The adaptive features of the ATC's then operate tapswitches 1-04 0 L L -' t- (see Figs. 1 and 2) to maintain the voltage wJ-hJn the voltage range of 14 area C. The higher voltage influences distribution ine capacitors controlled with ACCIs to switch OFF bringing the VArs measured by t1le ATC's to fall below Vo. Operation remains in area C until the measured VArs move below line VC where acain the s=. Z Of AZ2 is formed and compared %to Z1. When Z' is exceeded the oDeration returns to area A completing a loop of control action. 7 X_. curved arrow bel:Dw area C indicates the transition that occurs as area C expands downward; that is, the operation goes from area C to area A. The su"m Z is -eset zero when the change is made to allow time for the tapchanging operation to seek the voltage ES at the center of band A. An arrow below area A J ndicates similar move to area B. Arrows above area B show -%he transition to area A and above area A show the transition to area C. Note that operation does not change above area C or below area B but waits until time of day and other external factors bring the VArs within the control range.

A history of operation in area B is kept. Long periods in area B during Peak load times is an indication that all available capacitors are switched CLOSED and there is a need for additional distribution line capacitors.

COOR.DIINATED CONTROL OF TAPSWITCHES AND SUBS7ATION CAPAC7TORS Substations using LTC transformers to control output circuit voltage sometimes have power factor control capacitors switchable to the voltage controlled secondary outputs. Present practice is to control the switching of these capacitors with controls independent oz': the LTC voltage control and the distribution line power -factor capacitors. This is generally unsatisfactory because of the interaction of capacitor switching on voltage control. The present invention extends the ATC control of the LTC transformers voltages and interactive control of distribution line capacitors described hereinabove to further include 46 the switching of the substation capacitors.

At transnission stations having secondary capacitor banks on the output of LTC transforners it is desirable to control both the tapswitches to regulate voltage and the switching of capacitors to control the VAr flow through the transformers in order to avoid the improper action that can result from the use of separate ICI-apsw4Ltch and capacitor controls.

The control operation described in this section is also used at distribution substations having no lines feeding switched line io capacitors.

Fig. 17 in relation to Fig. 2 illustrates the -Lnven-L---Lve method of switching station capacitors 169 ON and OFF using ATC's 62'. The VArs flowing through LTC t-ransfor-mers 100 controlled by the ATC'c 62 JLs The measured by the ATC's 62 and forms the vertical scale of Fig. 17.

left hand portion of Fig. 17, marked 'SECONDARY VOLTAGE', shows the VArs as measured b-yr the ATC's 62. The range in VArs from VE to -VE is equal to the size of one sect-Lon of the station capacitors 169 and is imeasured each time the capacitor 169 switches as the changes in VArs from just.

before the switching to -ust after the switching.

The portion marked ITRA.NTSFORYIER LOSS DUE To VARS' ind'Lcates the variation in transformer losses with flow of VArs. Since no V.rs flow at point VO, the VAr loss at that point is zero. The capac.-JLtors are switched CLOSED and OPEN using ATC 62 outputs C(Close) and O(Open) respectively to sequencer 161 at the points indicated. As the requirement for VArs changes either up or down, the operation points as 47 measured bv ZITIC's 62 move u- and down betweeT-I- the po-J'_nts on Fig. - 17 marked CLOSED and OPEN. The choice of the points equally spaced about point VO produces the lowest-- average transformer 700 loss Over a Period of -Cime as limi-'Ced bv the size of the capacitor 169 sections. Other -1 ts may be required by system operating caiDacitor 169 sw tching poir, conditions but are expected to produce greater transformer losses.

As explained hereinabove under the discussJLon of Fig. 2 capacitors 169 may have several sections as sequentially connected and disconnected by state of the art-control 161. The in-,.7entive process illustrated by C) til al" are CLOSED Fig. 17 adds sections of capacitors 169 unk- _L as preferably is indicated by a closed contact 165 inDut FC to ATC 62.

S4 -Pilarly sections of capacitor 169 are OPE-,TED- until all are open as preferably indicated by a closed contact 164 input FO to ZkTC 62.

T'ne areas above -77E and belo-,,7 VE are adaDt_ively used to prevent is hunting due to smaller changes in measured vArs during a general trend in VAr flow requiring capacitor switching. Measured VArs, when wi-h4n 4 the areas, are _Lntegrated to a value adap-.ed to produce a selected weekly rate OIL capacitor switching and the integrals reset when the T measured VArs pass into the deadbands established between VE and -VE.

when the VArs measured by the ATC's move out of the deadband rhe itors are switched CLOSED and OPEN as indicated bv Fig. 17.

capac The areas above and below the deadhand are divided into quanta AZ of VArs convenient to integer math preferably equal to 1/8 of the VAr deadband. A sun Z is fornmed of LZ2. When ±his sirr, Z exceeds Z', the ATC 62 switches the capacl-tors CLOSED or OPEN as appropriate. The limit 48 Z' Is automatically adjusted daily by the ATC's so as ', 0 Produce a deS4 SW4 _.red weeklx-r ave-rage =7,ber of capacitor _tch operat-ion3.

The ATC tapswitch operation adapts as it does where capacitor 4 SW.tchl-ng is not used as described above in relation to Figs. 14 and is.

The non-linear timing brings the voltage change resulting from the capacitor switching quickly back one step towards the setpoint and more slowly back each succeeding step required. In other words, t-e ATC tapswitch operation responds to the voltage change caused by capa-itoz switching in the s;-:zme way as to any other voltage change and adaptiely .0 changes the speed of response so as to hold down the tapsw_J ch operations required yet maintain a desired quality of VRQF. Prio-r- a--t capacitor controls switch on small changes -in voltage and therefore ark-, , prone to switch incorrectly as a result of the tapchange control oDeration. The VArs sensed by the ATC for capacitor control are much i 5 less effected by the small regulated chances in voltage by the ATC's.

Furthe=.ore, the nonlinear timing c'L':: the ATC's adant to eliminating extraneous capacitor switching operations.

COMBINING TAPCHANIGER CONTROL, STATION AND LINE CAPACITOR SWITCHING Fig. IS is similar to Fig. 1.6 but adds substation capacitors 169 switched by swItches 160 as shown in Fig. 2, the switches opened by device 161 bv out,,)u-s 0 of ATC 62 and closed by device 161 operated by output C of ATC's 62.

Note that canacitors 169 may be a single section as shown in which case devices 161 merely opens and clcses switches 160 as directed by 49 output contacts 0 and C. Alternatively capacitors 169 may have more than one section in which case devices -1161 will have therequired external logic not shown for switching capacitor 169 sections CLOSED and OPEN in sequence. Several types of switches 161 and means for sequencing are in general use. The contact 0 and C action required to effect the sequencing of section of capacitors CLOSED and OPEN is well known and will not be described in greater detail herein.

Fig. 18 is similar to Fig. 16 but adds the VAr limit VE placed below VO by a value set into the control as equal to a multiple m (generally 0.5) of the size of one section of a capacitor 169 located at the substation along with transformer 100 and swiltchable by switches 160 to the transfo=er 100 secondary.

The portion marked 'TRANSFORMER LOSS DUE TO VkRS" ind-Lcal-es the variation in transformer loss with flow of VArs. Since no VArs flow at point VO, the VAr loss at that point is zero. The capacitors 169 are switched CLOSED and OPEN at the points indicated. As the requirement for VArs changes -ither up or down, the operation points as measured bV the ATC's move uD and down between the points marked CLOSED and OPEN.

The choice of the points equally spaced about point VO produces the : time as limited by ti7i e lowest average transfo=er loss over a period oj_ size of the capacitor 169 sect-4Lons. Other capacitor switching points may b required by system operating conditions as obtained using selected values for multipl-Jer M, but are expected to produce greater trans-former losses.

The existence of the substation bank implies that there are insuff--icient distribution line capacitors 119 to compensate for all distribution circuit load generated VaAs- Therefore after operation in area B no longer holds the VArs above limit VD, it is assumed that all line capacitors 119 have switched on. That being the case, as the VAr load grows, area B extends downward to 'Limit vE. The substation capacitor 169 is then switched CLOSED and OPEN as described above as described in the section titled "COORDINATED CONrLr1ROL OF TAPSWITCHES AND SUBSTATION CAPACITORS".

It can be assumed that the interaction of the added substation 0 capacitor 169 with the series impedance of transformer 100 will increase the transformer 100 secondary voltage. Therefore -it is expected that the inventive adaptive tapswitch operation will soon operate the tap sw4-1-ch L - - 104, if necessary, to return operation to region B. The resulting Vkrs are expected to be above VO by about one half the rating of the switched capacitor 169. Note that the previous switching on of all ava-i-lahle distribution line capacitors 119 plus caT)ac.4,-to"-?- 169 indicates a heavy load condition. It is very unlikely, therefore that any of the VArs JEed out of the primary will reach a generator where an unstable condition could result. operation within area A with increasing load can be 0 expected, in time, to fall below limit VD t-hus switching the setpoint to ES - I as before. With further increased load, VArs falling below VE will again produce an outputs of contacts C adding a sections of capacitor 169. This process cycle between areas A and B until all sections of capacitors 169 are connected if the increase in VAr load so requires.

51 As the load decreases the operating point moves above -VE and after an adaptive time contacts 0 will operate so as to rer.ove one section of capacitor bank 169 at a time. When all the sections are removed operation is transferred to area A by changing the voltage setpoint back to ES Note that operation remains in the lower voltage region B so long as any sections of substation capacitor 169 are connected. This line capacitors 119 that remain maximizes the number of distribution closed. In fact, the voltage may be lowered even further in response to transformer loading as described hereinabove. This further assures that all distributicn line capacitors 119 remain closed to correct power factors and to prevent distribution line load locations having less than minimal required voltages.

Assume the load decreases -Lowa--ds evening resulting with removal of all of caDacitors 169. Operation then continues in area A throughout the night, using area C as required to assure removal of distribution capacLtors 119 by operation of ACC's. Note that present praclCice often ibut-Jon capacitor to compensate the induct ve uses a single fixed distr, 41 exciting current of distribution c1rcuit step down transformers. Use of the -Lnventive methods described herein, iDer-mits use of all swltched dist-1-ibution line capacitors permitting the bank havi=. the lowest voltage to stay on at night for user step-down trans form er excit-ing current compensation and helps prevent excessive volt:ages that can occur during light loading conditions where fixed distr-ibution line ca-pacitors might have been used. The point where a capacitor can cause excessive 52 voltage may move from time to time as determined by nighttime loads and possible switching changes in the distr-Lbution circuit con-figuratior-1. with all capacitors switched by ACC's, this movement is of no concern.

Note that the above first scheme has the disadvantage that 'the control of VArs occurs during the daily peak load. An alternate second scheme is to switch the substation capacitors 1.69 on first and off last. This has the disadvantage of having the coarsest VAr control all of the time, even on days when, say only one section of the substation bank is needed.

The preferred scheme described in detail hereinabove has the advantage ofleaving the ACCIs available during the day to produce the best customer voltage profile and the least distribution power losses.

TYPICAL APPLICATIONS Figs. 19 and 20 compare the restricted VAr flow resulting from use of a load tapchanging transformer at a substation and ACC's along distribution lines fed by the transformer as described in Fig. 1 and the further restricted VAr flow resulting from -he use of load tapchanging regulators on each phase of a distribution line having ACCIs and -fed by reaulators as shown in Fig. 3.

In Fig. 19 transmission line 151 feeds load tapchanging transformer which then feeds three distribution lines 152. Each distribution line has three midway load tapchanging regulators 150, only one of which is shown. Many inductive loads 148 are shown along the distribution 1'Lnes. Three capacitor banks 119 are shown on each line 152 between the 53 transfo=er 1-00 and recullators -1-50 a.-).d three more capacitor banks between each of th_ree regul-at-ors 150 and the ends of the lines. Note that although one regulator 150 is shown rAdway in each of three lines 5, actually three are used in each locat ion, one onn each phase of lines SUlt4 152. Each of the re I-ng nine regulators is equipped with a,-.i inventive control 62., only one being shown at each of the three 4 flow Of 4 regulator locations. Many arrows 153 illustrate nducive VArs from loads 148 into capacitors 119 for correcti, on. Note that while no VAr current flows through regulators 150 due to the VAr control -features of associated controls 62, VAr current does flow through the co=on distribution circuit 152 connecting transformer 1-00 to the three rad 4 a! distribution lines.

Note that the capacitors numberea 119 in Fig. 19 are actualiv b a r "-.s of three; one for each phase with only one show-Jing due to the nature Of I Fig. 19, therefore does not 1 5 the single line representation used.

i ndicate which phase controls are connected to. For ci-_rcu4Lt-s fed by a three phase load -1--apcnanging transforrmer 100 as In F-Lg. 19f J- js preferred that all capacitor controls 139 be connected to the same phase PTC 62 so that any unbalance in phase voltage will not interfere with a s -_ - - L L - W_ the inventive relation of the VAr bias fl-_- -,T n. transfornaer 100 to the voltage sensed by ACCIs 139.

Fig. 20 shows, in 'Lull three phase fo=r, one of many radial lines at a distribution station fed from trans-,Liission lines i5l through fixed ratio step down transformers 149 and --egulato.7s 150 using iniventive controls 62, to each of three phases of: the linE. 152. Line 152 has a 54 midway regulator 150 bank of three regulators, one in each phase and each having an JLnven-4Ve control 62. VAr flow 'Lines 153 show load VArs flowing to the nearest capacitor 119 and not th-rough regulators 150 due to the use of VA.- b-Las techniques in each ATC 62 and the resultant response of ACC's 139. Note that no VAr flow is permitted (w-Lthin the discrete nature of the banks 119) from lines 152 a-Lid similar lines supplied by transmission lines 151 within the same substation as was possible in the system described by Fig. 19 above. Note that in practice, however, controls 139 on one phase may drive capacitor switches switching all three phases even though conL-rol 139 senses only one phase.

n 4 For circuits having each phase regulated by a -L-ndividual load tapchanging regulator as in Fig. 20, however, it is preferable that the controls be rotated between phases in a progression of capacitor is locations as further shown in Fig. 20 so that each regulator 150 ATC 62 will directly effect at least one capacitor bank. If there are less than three capacitor banks, then the VAr bias is only used on the regulator ATC 62 mat-ch-ing the placement of a capacitor control 139 phase connections. 20 AUTOMATIC POWER REVERSAL OF LINE REGULATORS.

The possible values of P range from a positive maximum to a negative maximum. Negative values indicate a reversal of. powe-- flow and is useful in revers:-na the operation of ATC's 62 should there be a reversal of power flow as sometimes occurs when regulators are used at -From eJ ther of two d, pcJnts of distribution iines alternat-vely fed Doin-ts Reference U. S. Patent applicat-ion Serial No. 152,001 describes a control useable with single phase regulators installed at a midpoint on d-Lstributior. lines as illustrated in Fig. 18. The reference patent describes keeping -track of the rec L_ _pulator tap positions and using a mathematical model of the regulator together with measured 'Levels of regulator load currents, computing voltages on what is no=ally the unregulated input of the regulators. The patent describes a method O.L low requiring a change in the control 0 dete=,.,-Lning a reversal of power ILE action. In the reverse condition it is necessary to reverse the raise and lower tap response to measured voltage. The line drop compensation action is also reversed so that it is functional in the new direction of power flow.

in this invention, the direct- measurement of P fo=s the basis of in-itiat-Jing the required control action upon detection of power reversal.

This involves two factors. Since P is measured 20 times per second (fo-T a 60 Hz frequency), the first factor is to average P using a recurs.-Lve equation of sufficient time constant to reduce anv f-ast jitter of the measured values of P. The second factor is to establish a small deadband either side of P = 0, where the sign of P changes Indicating a reversal of power. This inventive use of the direct measure of power -flow, P is used in olace of the method disclosed in U. S. Patent No. (M 2001).

The inventive determination of P provides an order of magnitude 56 improvement in -resolution of power reversal as compared to prior art methods usina 16 samples per cycle of AC waves.

Note that the internal impedances of regulators is much smaller than for LTC transfo=ers. For that reason the variables VP, VO and VS as used in determining VAr control as described in reference to Fig. 16 may reasonably be assumed equal to each other. The measurement of VArs related to the normal direction of power flow through regulators L therefore need not be reversed upon reversal of power flow through the regulators.

Since the ATC does not normally use 14 drop compensation but L g Drelera-bly uses the inventive changing of the regulated output volta e to influence the operation of ACC's, -Lh 4S operatC-ion is reversed so as always to influence ACC's on the power outpu-L side of the regulators.

Often it is adequate in practice -for a control to block a tapchange-r upon change in direction of power flow. This avoids hunting c- E the control since the control action changes from, degenerative to regenerative upon power reversal. This blocking action is easily accomolished in the ATC by a simple sub program responsive to the change in polarity of P.

CONTROL OF WAT"LIS LOAD ON DISTRIBUTION TRANSFORMERS when a power system becomes overloaded, it has been found that the Icad can temporarily be lowered by reducing -he voltage to the users of electric power. Since many appliances, such as air conditioners, may operate less effic"Lently at reduced voltage, the benefit of -reduced 57 voltagle may only last for a few hours; enough to relieve a load Peak caused by a weather condition. Once the load peak has passed, it is desirable to bring the voltage back to normal.

Furthermore, when load conditions permit it is desirable to raise the voltage. The increase in voltage may benefit users Of electricity in operating appliances whose efficiency increases for a small increase in voltage. The increase in voltage also produces added revenue to the electric utility. A carefully controlled increase held within the 5% range generally permitted by most state statutes is generally desirable under permissive conditions. An inventive strategy is to set the ATC operating setpo-int at, say 124.5 VAC. At this level the combination of the ATC operation disclosed he-l-ein together with the action Of ACCIs C 4 used to switch distribution circuit capa -Ltor banks holds the voltage along the distribution lines just below the upper 5% limit of 126 VAC requLred by most state statutes. In greater detail, the voltage regulation quality factor, VRQF, is defined herein and can be set into the ATC for a value of error voltage which when added to the setpo- intvoltage of 1.24.5 VAC suggested above will not exceed 126 VAC. For much of the year, especially in the spring and the fall when heaL---4Lng and air conditioning loads are low, these voltages can be maintained without exceeding generator or distribution transformer capabilities.

under conditions of heavier load it is desirable for ATC1s to automatically bring down the substation output voltage in small steps atindividual distribution transformers to prevent their overload whether or not a totall system overload load condition exists which could 58 possibly 'Lead to a voltage collapse power outage. This automation -e reduction made possible by the present invention sLa--Ls taking 1. t a Ij 4- 1 effect as a load increases in anticipation of a possible system overload. The cumulative effect of individual transformer adaption may correct a System overload condition avoiding or at least delaying use of the present practice of reducing the voltage at all substations as an emergency correction whether or not all individual distribution substation transformers are overloaded.

Individual transformer ATCI 62 sense, say, a load equal to the -.0 voltage by na-meplate rating of a transforme, and decrease the setpoinL.

a selected amount such as one volt. With further overload to, say 110% of rating in spite of the f 4 rst reduction, the ATC's 62 decreases the voltage an additional amount. Additional reductions to a lower limit, say 115.5 VA-C are automatically put into effec-L as the load increases indicates. Since the number of points of reduction in the inventive ATC's 62 is but a matter of the microprocessor program, no cost is created by the fineness of voltage reduction in response to transformer overload. Prior art controls are lim-ited by overall cost to one, two or three steos of reduction because of the additional hardware required.

'."he ACC's coo'cerate by closing capacitor s"17itches when the voltage reduction occurs. This improves the power factor as is generally reauired during an overload condition. When so switched on, power factor correction capacitors also tend to hold the voltage above the lower 114 VAC limit required by most state statutes at distribution circuit locations far from substations.

59 As the peak load decreases, generally iln the afternoon and evening, t4 Cally increased un-i 1 it is back, to e s,,iostation voltage J-s automa the original setpoint level.

Fig. 21 shows a nominal 120 VAC setpoin4C with 5% ( 6 volts) range permitted to the electric Utilit4 Les by most state statutes. Note that in Figs. 16 and 18, operation utilizes a three volt band. FJLg- 21 shows such bands with the centers marked 1 through 10 in one volt steps starting with ste'o 1 at 124.5 volts and ending with step 10 at 115.5 V"ts. The inventive control determines the temperature of the OL -'0 transformer and lowers the operating voltage center point from step 1 down to step 10 as required to reduce transformer over-temperatures. As the transformer goes below a set temperature, the operation moves back to position I thus minimizing variations in loading of the electric power system.

i5 With the lack of this automatic system, the reaction to overloading is of"ten delayed unt.-Il a system wide emergency lowering of voltage is This is often too late and power interruptions result. Preferably the trans"Ll'or-Laer temperature is measured direc±I tly and 'Led into the 7 TC control as an electrical analog or digital sJgnal. When such measurement is not available, the LTC control measures P. Th'Ls watts reading P is integrated using a thermal model of the trans-rZormer and the transformer temperature estimated. A measure of a-mbient temperature is required which is self contained within the control which then is preferably mounted outdoors with the transformer.

ADDING A FACTOR PROPORTIONAL TO THE SQUARE OF LOAD CURRENT Transformer load current flowing through tapswitch contacts causes deterLoration to the contacts generally believed to vary as the square of the current flowing when a tapchange is made. It is desirable, therefore, to make ATC's 62 respond more slowly to voltage deviations when the load currents are high and faster when the load currents are low. It is also desirable to block the tapswitch operation entirely for load currents above some limit IMax" This preferably is set just above a short. term overload rating of the transformer; typically 120% of the "transformer nameplate rating".

Fig. 22 illustrates an inventive method of accomplishing these current related factors using the following steps:

a) Increment and decrement timing interval H as described in greater detail in relation to Figs. 14 and 15.

b) Before comparing H to HF multiply H by:

3) i = (1 - (I/T max) 2)) C) If the new value of H is greater than H', then initiate a tapchange.

Fig. 22 shows how the time required to correct a voltage error varies as a function of transformer load current. Note that at load of 50% of Imax, the factor JLs one, assuming 50% as a weekly average load about which the limit HI will adapt. At no load, the response time to voltage variations decreases to 75% of the time at 50% load. At a load of 80% of T max' the response time to voltage variations increases by a factor of 4. At Imax the value of the H multiplier (equation 3 above) 61 becomes zero and currents at this value and above will block the tapswitch operation. Currants over I indicate a syst-em fault or a r max serious abnormality at which time the loss of a transformer tapsw4tch L would greatly compound an already difficult condition. Blocking the S tapswitch operation is therefore acceptable at overload currents. In contrast to the present invention, prior art systems generally use an overcurrent relay which has no effect until the pickup value of current is exceeded.

Computations are performed just following the measurement cycle.

io when compu-L--- at ions are complete, communications is performed if a request has been received or if the progran, within ATC 62 calls for a communication outward. Communications is preferably done at high bit rates with a single packet of data.

CoIiDIUNICALTTONS Fig. 23 is an isometric view of the inventive ATC's 62 illustrating the use of palm top and lap top computers 903 as the man-machine interface (MI). In addition to eliminating all but a few infra-red diodes 904 for indication of ATC operation, these man-mach-ine interfaces selectively uses two way J'Lnfra-red ports available on palm top and lap top comDut- ers. These are matched with two wav infra-red port 901 on ATC's 62.

Alternatively communications is prov-Lded by way of a plug in wireless modem 902 using PCMCIA receptacle 900. This is discussed further hereinbelow in the discussion of the use of Internet.

62 A third alternative is the use of an adapter responsive to weil known selected SCADA protocols.

RECORD KEEPING Use is made of the computing power of external computers using one or more of the alternative communications means to replace ATC programming wherever possible, thereby further reducing the size of the ATC programs.

While the adaptive features of the ATC virtually eliminates the t 4 io need for communica _Lng to the ATC, the inventive LTC control is capable of generating vast amounts of data, often far beyond the amount capable of human examination and use. The data is most useful, however in analyzing a system disturbance such as a voltage collapse event often resulting in loss of service to parts of an electric power network. An inventive system is described hereinunder 'An which data may be held JLn the LTC control until requested.

Data is recorded in memory of the LTC control at many equaliv spaced intervals RT during a day, the intervals preferably being one to four minutes. Preferably the data includes:

* File A. Averages EMA of AC voltage measurements EM calculated over periods equal to intervals RT. Preferably the average EMA _Js obtained from a recursive equation:

4) EMA' ( (NM - 1) EMA) + EM) IN"MI where EMAI is the new average voltage after obtaining measurement EM and EMA is the average before obtaining measurement EM, and where INM 63 is the nu-mber o-E measure.-Lp.ents in time period RT.

Not-e that external con.puters receiving files of EH3, data -aay compute Voltage regulation quality factors VRQF over intervals RT by:

5) VRQF = ((Z(EM - ES)2)/NM);l where ES is the voltage setpoint.

File B. Average measured Watts WMA over time period RT preferably using equation 6).

6) WIMA = ( (NM - 1) WRA) + EM) INMI File C. Average measured VArs VMA over time period RT preferably io using equation 7).

7) VMAf (NM - 1) VIKA) + EM) /IZIM Preferably this data is recorded in non-volatile memory -in blocks of a single day's data. Preferably the day starts and ends at midnight with the dav's, date entered at the start. of each dav's block-,.

-"a are saved for selected =-Lbers of days. -he process Blocks of daL.

is described here-inbelow illustrating the use of eight blocks for one week of data.

The blocks are identified for purposes of illustration as follows:

Block 0:' today's data from midnight to time of request for the data.

Block 1: yesterdays data.

Block 7: data for a week ago today.

At midnight block 7 is erased and reidentified as block 0 with other blocks moved up by adding one to the old number.

64 This data is accessed upon demand using the IR port with a compu.er having an IR por"Z_, by use of the wireless modem as described here inbelow and by use of a SCADA interface device.

A selectively alternate or additional recording is to record fine grain voltage, Watts (P) and VA_r (Q) quantities with integrating time periods in the order of one second and for periods in the order of, say minutes. This data is particularly useful in substantiating reasons for the previously mentioned voltage collapse failure of electric power service. There is an unsubstantiated theory that such failures may -io result from the cascading of induction motors stalling due to low voltages. As is well known, fully loaded inductions motors will st-op turning at voltages typically 70% of rated voltage. A stalled motor will draw heavy lagging current further contributing to lower voltages along a power distribut'Lon line. Thus one motor towards the far end OIL j and so on. lany motors may a line may cause an ad acent motor to stall, M remain stalled for several seconds until over-temperature relays --emcve their -owe-source. The protection is sufficiently slow that a do-mi-no effect of motor stalling may overload a distribution line branch until a iffuse blows. wide spread repetition of this effect may theoretically bu L. L 4- - - con r, -e -o a voltage collapse interruption of power over a wide range. No data has been reported to the industry, however to ei-I-Inier prove or disprove this theory. The inventive recording of the data as described here may provide understanding for the correction of voltage colla;Dses caused by motor stalling.

This fine grain data recording is best done using timing intervals convenient to the microprocessor programs and to the use of the microprocesscr memor-y. Integrating times need not be precisely one second and is varied to best pack the data into blocks of memory as required for the type of the memory chosen. Such data Packing also contributes to the com::iunicating of the data in serial digital strings compressed with little or no wasted space.

Preferably the fine grain data is stored in flash or other non volatile memory so as to be available after a power interruption that may follow a particular pattern of variation of voltage and P and Q components of power flow. in addition the length of time before the fine grain data is overwritten is a function of the efficiency in the use of the memor-Y and the amount of memory available. Pre-ferablLy this data Ls communicated automatically, using one of the ways described above, following a power interruption of greater than a selected time.

2. 5 This automatic communications prevents useful data -L;- r o m teing over-written as the power returns to normal.

COMMUNICATING DATA TO THE INTERNET The data is entered into Internet via a wireless modem where it is 0 L then available to computer users at many locations in the effected network desirable of analyzing the system disturbance so as to minimize effects of a reoccurrence of the disturbance.

The digital data is sent from the LTC ATC 62 via wireless modem 902 (see Fig. 23) using radio signals between the ATC 62 and regional radio towers capable of sending and receiving digital signals over a radius of 66 some 20 miles. From the regional digital signals are exchanged with a central digital signal dispatching station capable of entering data into Internet as messages accessible to users of Internet.

Modems 902 available for the radio signaling include a Motorola 100 D device. These plug into PCMCIA receptacle 900 in the LTC ATC 62 using parallel interfaces with the microprocessor 1 (see Fig. 5).

Alternatively Motorola Envoy devices not shown are used for the radio signaling devices using a serial interface with the control 62.

The regional means and the central dispatching station are -ions Network in turn using a typically provided by an Ardis ComnunicaL. Rad-iomail interface with the Internet.

A master user of Internet may request all blocks; any one block; and any file A through D as described hereinabove. This master user determines the comm unic at ions costs in the selection of data to be transferred. once transferred, other users of Internet can use the data With nore minimal Internet charges.

ADAPTIVE TAPCHANGER CONTROL TEST SETUP Adaptive capacitor control (ACC) production equipment that is patterned along the lines of the invention disclosed in U. S. 'Patent 5,541,498 has been successfully tested on Florida Power Corporation distribution lines.

A test setup was installed which included controls connected to 120 volt outlets at locations served by Florida Power Corporat'Lon distribution lines. These controls sensed, and responded to, the 67 voltage variations created by Florida Power customers as they turned roorm the=osta"C-s up a.-Lid down, as air conditioning equipment responded to daily and seasonal fluctuations in temperature. It was found, for example, that whether or not the sun was shining was a major factor on the voltage a.-Lid in turn in the operation of the adaptive capacitor controls. The test setup involved the varying of scaling factors and other details of the non-linear adaptive process so as to properly respond to the very complex behavior of many persons living and working in the area served by the distribution lines from which the controls received their power.

Adaptive tapswitch controls were combined with the inventive technology disclosed herein, and the following additional tests were carried out using the utility customer generated voltage variations on a Florida Power Corporation distribution line.

i5 A 120/240 volt service was connected to the test setup from a 25 KVA transformer on a 13 kv circuit service. This service was free from loads other than the test connections to be described. In this way the test setup responded to the fluctuations in the 13 kv distribution voltage virtually independently of the load on the service transformer since the test equipment load was kept very small and nearly ncri variant.

Fig. 25 shows this service and Fig. 24 shows in the test setup to measure the improvement resulting from the inventive adaptive LTC control described herein.

In Fig. 25 transformer 201 steps down the nominal 7,500 VAC of the 68 1.3 Kv (phase to Dhase) distribution line 200. This distribution line feeds 3 phase power to a customer throug-h. three transformers 204 via conductors 205 to entrance 206. The single phase 120/240 volt service for the test setup work is carried over conductors 202 from transformer 201 to entrance 203.

Fig. 24 shows entrance box 175 for the single phase service feeding voltage via conduJLt 174 to regulators T1, T2 and T3. This provides for tests with three single phase regulators.

Terminals 176 of the regulators are the neutral terminals, terminals 177 are the unregulated input terminals. In this setup terminals 177 are supplied with unregulated nominal 120 VAC from the experimental supply shown in Fig. 25. Terminals 178 are the regulated output terminals of tl,-Le regulators.

Regulator TI is controlled by tapchanger control 180 which comprises a Beckwith Electric Co. M-0067 control as described in U.S. Patent 3,721,894. Control 180 senses the regulated 120 VAC directly from -Cernzinal 178 rather than from a step-down transformer normally used. Control 180 is set at 120 VAC with a two volt bandwidth, secondL time delay using the standard timer and non-sequential operatJI-on. In th-:Ls way, the timer resets after each tap change, integrates upward when the voltage is out of band and resets when the voltage is in band.

Regulator T2 is controlled by tapchanger control 171; a Beckwith Electric Co. M-2001 control which is described U. S. Patent (S.N.

08/152,001). Control 171 senses the regulated 120 VAC directly from 69 terminal 178 rather than from a step-down transformer normally used.

W4 Control 171 is set at 120 VAC Lth a two volt bandwidth, 120 second time delay using the integrating timer option and non-sequential operation. In this way, the timer resets after each tap change and integrates upward when the voltage is out of band and downward when the voltage is in band.

Regulator T3 is controlled by the inventive ATC 339 as described herein. Additional ATC's 139 and 239 are connected to regulators T1 and T2 to gather data only. All three controls 139, 239 and 339 measure the voltage each half cycle and compute two recursive averages of VRQF; the first having a short term and a second being a recursive average of the first recursive averages having a long term. In addition, a third recursive average of voltage having a short term is computed. The first and third short term averages are recorded for study of the ATC's behavior.

Equation 5) hereinabove is used in computing the first and third averages VRQF using chosen time constants which are binary numbers providing a tine constant of approximately two minutes. Binary numbers are chosen for convenience in dividing by shifting the binary point in the control 139 microprocessor program.

In using equation 5) AE is the difference between the measured voltage and the band center voltage, which for all controls in this test is set to 120 VAC. Note that the squaring process produces only positive answers, independent of whether the voltage error is above or below 120 VAC.

The ATC 62 computes the second recursive average providing a one week time constant referred to as the weekly average available for readout using computer 73 whenever requested. In early stages of the tests, HI was adjusted manually so that ATC 339 gave the same weekly average VRQF as the M-2001 control 171. In later stages of the tests H, is adjusted adaptively to produce a VRQF of 0.4, that being the value obtained in the earlier stages.

The binar-y number 8192 is proper to use in equation 5) in a control which is measuring only voltage. In such a control, using the SLIM' technology disclosed in U. S. Patent No. 5,544,064, every cycle of the AC wave is measured and used in the first equation 1). In a control using both voltage and current in making measurements, computations such as of equation 1) are made every three cycles giving 20 measurements per second; 1,200 per minute and 2400 in two minutes. T.I-.e binary number, 2-048, is then used in place of 8192 in equation 5). Note that in the SLIMtechnology, the samples of the AC waves is synchronous with the ADC for greatest efficiency of the sampling process, the computation and communications period is accomplished within one half cycle so as to make the packets of measurement, computation and communications synchronous with the AC frequency. The counting of AC cycles then becomes the prima-,y method of measuring times such as the two minutes and one week chosen for the short and long term recursive averages.

Adaptive controls 139, 239 and 339 located on regulators T1, T2 and T3 compute the same recursive averages of the voltage error squared and communicates these to computer 73 where the short. term average is a-'lable as a time plot and the -Iong term average available as a va L for all three regulators T1, ntu-iber- Note that the measurement of VRQF T2 and T3 are obtained using identical ATC 139, 239 and 339 hardware and programs and identical computer 73 processing of data so as to fairly compare the rates of tapchanges of the three regulators.

Controls 1391 239 and 339 have set deadbands of 1.0 VAC and set voltage limits 6 VAC above and below the band center voltage (herein 120 v,kc). when the voltage is above the deadband DB of Fig. 15, "H" times upward nonlinearly and when the voltage is in the deadband DB, "HII times downward at a selected rate. This adjustment of IIHII occurs after each synchronous measurement interval until either:

a) IIHIII is exceeded in which case the tapswitch is moved down, (T3 only) or b) the voltage moves below the deadband DB in which case IIHII is ro reset to ze?,.

When the voltage is below the deadband DB, IIHII times upward nonlinearlv and when the voltage is in the band, IIHII times downward at a selected rate. This adjustment of IIHII occurs after each synchronous measurement interval until either:

a) "Hr, is exceeded -Jin which case the tapswitch is moved up (T3 only) or b) the voltage moves above the band in which case IIHII is reset to zero.

The non-linear process substantially identical to the one disclosed in U. S. Patent No. 5,541,498. while the present invention discloses 72 the fundamental concepts for making adapt to a desirable value, the test setup provided data to refine the deta 4'ed adaption algorit,,Lms for IIH I IT therefore in earl-Jer stages of the test "HIT' was adjusted -manually.

The VRQF is obtained using computer 73 and HI changed daily in ATC 339 on regulator T3 until the measures of voltage quality from regulators R1 and R2 is equal to the voltage quality from regulator R3.

Ncte that the voltage quality from regulators R! and R2 was found to be nearly equal with the settings chosen for them as described above.

operations of regulator R1 by the M-0067 control and regulator R2 by the M-2001 control were found to produce very nearly the same VRQF.

HI was varied in control 339 to match and the daily average number of tapchanges in the three regulators were compared. The rate of operations of regulators T1 and T2 were found to be nearly equal and the rate for regulator T3 was found to be approximately 40% less when a value of HI was found giving the same VRQF in all three regulators.

Fig. 26 shows a 24 hour plot of the regulated voltage Produced on July 10, 1996 by a ATC sell--- for a weekly average VRQF of 0.4 volts rms.

The tine scale is for a 24 hour period starting at midnight.

Fig. 27 shows a 24 hour plot o'E VRQF's with two minute tine constants corresponding to the voltage plot of Fig. 26.

The following table gives additional test results corresponding to the data shown in Figs. 26 and 27. The weekly average of tapchanges per day Ls for the week preceding July 10, 1596. Note that Hf of the ATC was adjusted manually to bring the weekly average VRQF of the M-2001 and 73 the ATC together. The M-0067 was adjusted for the same bandwidth and timeout setting as the M-2001 with no further effort to balance the VRQF produced by the M-0067.

CONTROL WEEKLY AVERAGE NUMBER OF TA.PCHA.NGES WEEKLY AVE VRQF DAY OF FIGS. 26&27 TA.PCHANGES PER DAY -0 M-0067 0.512 27 23.0 M-2001 0.413 26 21.7 ATC 0.408 14 14.8 ADVA.NTAGES OF THE INVENTION 1. Reduced number of tapchanges required to obtain a desired quality 04L voltage control.

2. improved voltage control resolut 4L o n 3. measuring and minimizing VAr flow by voltage bias influence on distribution line ACC switching.

4. Coordinated control of substation capacitor banks and LTC transformer taDswitches.

5. Adaptive algorithms are superior to, cannot be duplicated by human control and eliminate most human control.

-.5 6. Provision of selected -oeriods of high resolutJI-on data on da--';. -',y voltage control with any days data callable on demand such as i-n-to Internet for wide distribution.

7. Fine grain voltage data collected and following a power interruption held for recall within a selected time for analysis such as following a wide area voltage collapse blackout.

8. Correlating fine grain data with library of voltage templates 74 to determine need to trip load shedd---ng circuit breakers.

n While the invention has been Particularly s,_ow and described with reference to a preferred embodiment thereof, it will be understood by those skilled in the art that various changes in fo:m, and in details may be made therein without departing -from the spirit and scope 0-f the invention.

i 5

Claims (6)

CLAIMS:

1. A method of ufIlizing many samples of alternating current (AC) voltage signals and AC current signals to directly measure the P and Q components of the flow of AC electric power, the method consisting of the steps of a) taking predetermined numbers of digital samples during positive half cycles of AC voltage signals, b) providing tables having double said predetermined number of values of one cycle of a sine wave equally spaced 'in angle and arranged to be read as a ning starting at any selected point in said ring of values, _ 9) obtaining the fundamental component of said voltage signals by summing products of said samples with values from said ring starting at the point where the values change from negative to positive and ending at the point where the values change from positive to negative, d) taking double said predetermined number of first samples of current signals, e) continuously summing products of said first samples of current signals h 0 t values of the sine wave starting at a first poffit on said ring selected to give the P component of power, f) taking double said predetermined number of second samples of current signals, and g) continuously summmig products of said second samples o.,L'current signals with values of the smie wave starting at a second point on said ring spaced 90' from said first point to give the Q component of power.

2. A method as in Claim I further including the steps of a) obtaining values for P and Q using a second current, and b) comparing ratios of P and Q for the two currents and determining which current is earlier 'in phase sequence.

3. A method as in Claim I further Micluding the step of using the change in value of P from positive to negative as an indication ofIr,--versal of power flow.

0

4. Apparatus for the direct measurement of the real, P, and imaginary, Q, components of alternating current (AC) electric power using AC voltage and currew signals comprising in combination, a) microprocessor means Micluding central processors unit (CPU) means, memory means, analog to digital converter (ADC) means, result register means, and analog to digital control logic (ADCTL) means, b) ADC means for providing diolital samples of positive half cycles of said AC signals, c) program means for setting said.ADCTL to continuously sample said AC voltage signals and place results in said result register, d) measurement means operating synchronously with said continuous sampling, e) means for providmig values of sine functions from a ring of an integral number of sectors of N values per sector with the total number of values equaling the number of samples expected from one full cycle of said AC signal at an expected power frequency, f) means for multiplying values from said ring over a selected range of 180 of said ring with samples from said result register as they are taken and summing sid samples to measure the filndamental frequency component of said AC voltage al -D signals, g) means for setting said ADCTL means for continuous sampling of said AC current and placing results in said result register, h) means for multiplying values from said ring over a first selected range of 360'of said ring with samples from said result renster as said samples are taken and summing said products to measure the P component of said AC power, and jJ) means for multiplying values from said ring over a second selected 360 ranae rotated 90 _4-om said first range with samples from said result register as said samples are taken and summing said products to m%easure the Q component of said poyver.

5. Apparatus as in Claim 4 further comprising in combination:

a) means for connecting a second current signal to said.ADC means so as to obtain digital samples of positive half cycles of said second current signal, b) means for obtaining second P and Q cor--ponents using said voltage signals and said second current signals, and c) means for comparing ratios of said first components to ratios of said second components and thereby determining which current led the other in time phase relationship.

6. Apparatus as in Claim 5 ftirtlier comprising in combination- a) means for controlling voltage tapebanging switches on LTC I.-.-ansf-b- inner means with secondari-es paralleled and with each transformer controll sensing, said transformer load current touether with load currents of next paralleled transformers 'in dalsv chain arranaement around I-Migs of said paralleled transformers, b) means for sensing first P and Q components of said transformer load current, c) means for sensing second P and Q components of said next paralleled transformer load current, and d) means for controlling said tapchanging switches so as to maintain ratios of sai first P and Q components equal to said second P and Q components whereby losses introduced by parallelmig are ml'nlmlz%-,d with or without having transformer primaries in parallel.