CA1285615C - Electrical power line and substation monitoring apparatus and systems - Google Patents

Abstract

Abstract Of The Disclosure Disclosed herein are individual sensor modules for mounting directly upon energized electrical power conductors and systems employing such modules, with principal emphasis upon the provision of both data transmitting and receiving means in each sensor module and at an associated ground station. The modules sense the instantaneous values of all parameters necessary to perform complete metering functions and, in one embodiment, are synchronized by a signal transmitted from the ground station and received by all modules so that the values are measured simultaneously on all conductors at a substation. The signals are transmitted by the modules in a time-synchronized manner and are in

Description

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This invention relate~ to apparatu3 ~or mea~uring operating parameter~ of high voltage power conductors and, more particularly, to sy~tem~ employing sen~orq which are mounted on overhead power tran~mission line~
~or measurin~ all parameterq nece~ary to monitor operation o~ ~ingle pha~e circuits, three pha~e circuits, and an entire electrical power sub~tation.
The ~ensors normall~ derive their power aq a reqult of current ~lowin~ through the power conductor, and the invention ~urther relates to back-up power mean~ ~or operating the ~enqor~ ~hen there i~ little or no current flow through khe conductor.
Varlou~ power line ~en~ors have been diqcIosed in the prior art. For example, the sensor~ of United State~ Patents Nos. 3,428,89~, 3,633,1915 4,158,810, 4,268,818 and 4,384,289 have been propo~ed f~r dynamic line rating o~ electrical power tran~mi~ion line~. The power line qen~or ystem~ a~ailable in the prior art mea3ure certain quantities a~jociated with the operation of an indi~idual overhead conductor, namely, current f}ow in the conductor, conductor temperature and ambient temperaturel The limited information gathered by a , . . .. ___ .

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, ' ' s ~ingle ~enqor module i~ transmitted to a local ground ~tation dedicated to that ~ensor module. Data ~rom various ground receiver~ i3 transmitted to a central control ~tation where the in~ormation i~ analyzed.
Sen~or module~ of the prior art, although providing a means o~ measuring certain operating parameterq of individual conductorq, do not provide a mean~ ~or simultaneous measurement of multiple parameters and communication of data ~rom several ~en~or module~ to a ~ingle ground receiving qtation. Thus, prior art ~en~ors ~or monitoring tranqmis~ion line~ have not had the capability o~ ~imultaneously and accurately mea~urlng voltage, current and phaqe angle on a single phase or cooperatively on all conductors of a 3-phase circu~t. Likewise, prior art ~ystems employing line-mounted sen~or modules do not have the capabil~ty o~ mea~uring and communicating all operatin~ parameterR
involved in monitoring an entire substation through a single, microprocessor controlled ground 3tation receiving data from a plurallty of ~ensors. It ha~
there~ore remained neaes~ary to pro~ide ~ub~ation :
: ~ monitoring in the conventlonal manner, i.e., by ~eans o~
ndlvidual current and potential transformers on each conductor at a ~ub tation where each tran3~0rmer is hard-wired to auxiliary transformer~ on the ground whereln the signals are oonverted to a level compatible with various tran~ducer Individual transducer3 are ~ ~ .

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required to mea~ure each parameter, ~uch a3 voltage, current, kilowatt~. These 3ignal~ then pa~s through an array o~ te~t ~witche~ and terminal blocks which in turn are hard-wired to a Remote Terminal Unit (RTU).
It i~ a principal ob~ect of the pre~ent invention to provide a ~en~or module for mounting directly upon an energized power conductor and capable o~ measuring simultaneously the voltage, current, frequency, pha3e angle and other parameters on the a~sociated conductor and communicating khe value~ thereef to a rece~vin~
station. The received ~ignal~ may be Purther proce3sed to provide other data a~30ciated with a single pha~e or with one or more 3-phase circuits.
It 19 a fur~her ob~ect to provide an integrated ~ystem ~or monitoring parameters a~sociated ~ith operation Or an entire electrical power ubstation u~in~
only line-mounted modules, each capable o~: :
~imultaneou~ly ~en~ng the voltage, eurrant and pha3e angle on the a3~0ciated conductor at a predetermined time and communicating the mea~ured quantitis~ to a single ground ~tatlon microproce~or. The ~ensor module~, of cour~e, are o~ a type which may be mounted dire~tly upon energized oonduotor~g requir~ng no ~hut do~n of the circuit during in~tallation. Furthermore, th~ signal~ communicated ~rom the modules to the ground station are in a conditlon ~or u~e directly by the ieroproce~sor, thereby eliminating the need ~or __ . -- ~ ,~ :. , .. ~ .. _ _. _.. ,_ .~ . . , . _.. _~ ._ .. _.. .. .. __ .. _ .. .. ... .... _ _ _.. .. _ ,_ _ __ ____ _ ...:. .~. .- ~ -: :
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': ' auxiliary tranq~ormerY, transducer3, and the like, nece~ary for ~ignal conditioning and proce~ing in prior art sub~tation monitoring 3y3tems.
Prior art 3ensor modules, such as the toroidal~haped modules of previou31y mentioned Patent No. 4,384,289, derive thelr operating power dirsctly from the conductor~ upon which they are mounted.
Con~equently, they are operable only when the line current of the oondu¢tor i~ at or above the ~inimum value neces~ary to power the ~ensor electronics. In a ~ub~tation monitoring ~y~tem of the type contemplated by the present lnvention, it l~ neceq~ary that the ~enqor module also be operable when line ¢urrent~ are below the threshold level, i.e., ~or monitoring very low current oondition~ or detection o~ energized condu¢tors with zero ourrent flo~. Therefore, It i~ an ancillary ob~ect o~ the invention to provide a reliable power baok-up y3tem, requirlng es~entially no removal and/or replacement o~batterie~ for recharging, ~or operating line-mounted 3en~0r modules.
In a sy3tem wher~e a plurality of modules tran~mit data to;~a slngle receiver it 1~ desirea~le to provide meanq for in8uring that more than one ~ensor i3 not .
tran3mitting at any given time. It has been proposed to ~ran~mit ~i~nal~ in bur~ts of finite duration at random imes, but there is qtill the pos~ibillty that more than one sensor will be tran3mitting at a given time. It i9 ~ ~ :

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' : . , ~: . , : ' ~_~.d ~ 5 an additional object of the present invention to provide mean~ ~or time synchronizing data tran~mi3~ion~ ~rom a plurality of ~ensor module~ ~o that no two modules are tran~mitting at the same time.
Furthermore, lt i~ an ob~ect o~ the invention to achieve this through sel~-contained mean~ within each module precluding need for communication between module~
or requiring a ~yn¢hronizing signal ~rom the ground ~tation, called the combined CRTU~
Other ob~e¢t~, related to the foregoing, will in part be obvious and will in part appear hereinafter.
Summary 0~ The_Invention The pre~ent invention contemplate~ a po~er monitoring system compri~ing a sensor module capable of ~imultaneou~ly measur~ng the voltagej-: current and phase angle and other parameter~ o~ a power conductor (or in its vicinity e.g. amblent condition~) upon which the module i5 mounted and ~or communicating such data to a ground ~tation. The invention may be expanded to include ~y~tems wherein one ~uch module i~ mounted upon each conductor to be monitored at a power su~station .
wlth qelP-contaLned qynchronization means or mean~ ~uch : a~, RF reoei~ers of po~er line carrier coupling provided ` to oause all ~en~ors in the ~y~tem to meaJure the value~

: ~ oP voltage ¢urrant, pha~e angle and ~requency, on the ~ a~sociated condu¢tors simultaneously at predetermined : ~ times. The sen~or module~ are conneoted by a ~ __ . . . _ . _ _ _ . _ _ . _ .. _ .. . .. , .. .. : :.. .. , . .. __. _.. ....... .. . ..... .... . _ .. . . . .. ... _ _ __ _ . ... , . . , . . _ . _ __ .

~ 5 communication~ link, such as RF transmitters and receiverq, to the ground ~tation and are adapted to convey qignals commensurake with the mea~ured parameters qequentially to appropriate qignal receivlng meanq on the ground. The ~ignals in their a~-received condition are ~uitable ~or supply to a micro-processor wherein all de~ired quantitle~ which may be derived from the values of voltage, current and phase angle o~ the various conductorq, ~uch as, megawatts, me~awatt-hours, megavar~, power ~actor, etc., are developed and the re ulting in~ormation is communicated with other in~ormation in a manner similar to a conventional ~TU
but employing a single microproces~or. Thus, the invention eliminate~ the need not only ~or current and potential tran~former~ wired from the re~peotive oonductors to auxiliary transPormers on the ground, but al~o an array o~ tran3ducers, te~t switche~, terminal block~ and hard wiring repre3enting literally tons o~
equipment pr~viously required for monitoring operation of an electrical power substation.
: The ~en~or module~ alqo pre~erably include electrostatically or electromagnetically line powered, rechargeable battery back-up ~acility ~or powering the module electronios when there i~ minimal or zero current on the conductor upon which the module i3 mounted.
Current qenslng circuitry in the module monitorq the level of current on the conductor to e~tabl~sh whether ~ .

_;. ... _............. ~ 6 ~3S~;~5 rhe curren-t is above or below a predetermined threshold value.
When current is above this value, the sensor is powered by electromagnetic induction from the conductor, which also serves to float charge the battery. When line current is below the threshold value, or when the conductor is energized but current is zero, as determined by voltage sensing circuitry, power is supplied to the sensor by the battery. If the zero current condition persists beyond a predetermined time limit, battery control circuitry and a processor in the sensor module operate to reduce the frequency of data transmission from the module to the ground station receiver, thus conserving battery power. If battery voltage drops below a predetermined level, all battery-powered transmission is stopped until the batteries are sufficiently recharged. Also, when current on the conductor i5 at or above zero but below the threshold level, the battery is float charged electrostatically between data transmissions.
Generally speaking, the present invention may be considered as providing a system for monitoring a plurality of ~ parameters associated with each of a plurality of energized - 20 electrical power conductors, one of the parameters being conductor voltaye, on power system circuits operable over a load range between predetermined minimum and maximum conductor currents in either direction for complete installation and removal while the conductors are energized, the system comprising: (a) a plurality of sensor modules each having a metallic housing, one of the modules being mounted upon each of the energized conductors, the housing being conductively isolated from the conductor at least for frequencies below the ~J:lcm 7 :

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~35~5 niyhest fre~uency of conductor voltaye to be measured, whereby the surface of the housing continuously collects the charging current due to the electrostatic field associated with the conductor; (b) means connected between the conductor and the housing for measurement of conductor voltage from the charging current; (c) means contained within the housing for continuously sensing the current through the conductor over the entire loan range; (d) means carried by each of the modules for establishing the phase relationship between the sensed values of conductor voltage and conductor current; (e) means carried by each of the modules for identifying, processing and storing the sensed values of conductor voltage and conductor current and the established phase relationship; (f) means carried by each of the modules for transmitting a sequence of encoded signals commensurate with each of the sensed values and including the established phase relationship and sensor module identification;
and (g) means remote from the modules for receiving the signals from each of the plurality of sensor modules, decoding the signals and calculating voltage, current and power ~actor of each of the conductors.
Furthermore, the present invention contemplates a system for monitoring a plurality of parameters associated with each of a plurality of energized electrical power conductors for complete i.nstallation and removal while the conductors are energized, the system:comprising: (a) a plurality of sensor :; .

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~ ~5~5 modules, one of the modules being mounted upon each of the energized conductors; ~b) means carried by each of the modules for sensing values of a plurality of parameters of the associated power conductor; (c) means carried by each of the modules for identifying, processing and storing the sensed values; (d) means carried by each of the modules for periodically transmitting a sequence of encoded signals in data bursts of predetermined duration from each of the plurality of sensor modules commensurate with each of the sensed values; ~e) means carried by each of the modules for controlling the starting times of the data bursts by the transmitting means of each of the modules to avoid simultaneous transmission, with consequent data collisions, by any two of the modules; and (f) means remote from the modules for receiving the signals from each of the plurality of modules and decoding the signals to provide the parameter values at the remote means.

Brief Description O~ The Drawin~s Figure 1 is a diagrammatic illustration of a typical electric power substation incorporating the present invention;
20Figure 2 is a view of a p~rmanent or semi-permanent : sensor module embodying the present invention being mounted on : a transmission line;
Figure 3~ is an enlarged, perspective view of a ~ : , :~ 7b ~ ~ JJ:lcm :~ .
~ : ' , S~5 ~en~or module mounted; on a conductor;
Figure 4 i~ a view of the sen~or module of Figure 3 in a oro~s ~ection through the plane of the conductor;
Figure 5 iq a general block diagram of the senqor module electronic~;
Figure 6 i~ a ~chematic diagram illuYtrating the power supply and rechargeable power back-up ~y~tem of the pre~ent lnvention;
Figure 7 is a ~chematic diagram of` the voltage ~en~ing mean~ of the invention;
Figure 7A i9 a ~chematic diagram of an alternate voltage ~en~ing mean3;
FiBure 8 i3 a detailed block diagram of portion~
o~ the ~oduls ~hown generally in Figure 5;
Figure 9 iq a graphical d~piction of the voltage wavefor~s of She three cycle of each o~ a plurality of circuit~ ~onneated to a ~ub~tation bu~;
Figure 10 ind~eate~ the relation~hip o~ the ~heet~
containing Figures lOA and 10B to Porm a single block diagram;
Figures 10A and lOB ~orm a compo~ite block diagram of the ground qtation electronic~; and Flgures 11A and 11B provide a diagrammatic compari~on of the monitorlng sys~ems o~ the prior art and the pra~ent inventionO

Re~erring now to the draw~ngq, in Figure 1 i~
~hown a diagrammatic repre~entation of an electrical power ub~tation enelo~ed by ~tation fenoe 9 ~ employing ,.. _, .. .... .. :, .. _ .. .... . . .. .. .. . _ _: . ., .. .. .. . __ _ _ . _ _ . _ . ~ _, . . ._ _ _ _ _ _ _ _. _ , the pre~ent invention~ A plurality of three pha~e circuit~, numbered 1-8, are fed from a common buq compri~ing three pha~es 10, 12 and 14, each connected through circuit breaker 16 to tran former bank 18. The latter is fed by an lncoming three-pha~e power circuit comprising three conductors denoted collectively by reference numeral 20. Sen~or module~ indicated generally by re~erence numeral 22, and having a structure and operaSion desoribed later in more detail, are mounted upon each o~ the three pha~e~ of line 20, and o~ l~ne 24, çonn~ctlng transformer bank 18 to breaker~ 16. Conduator~ for each phase of all 3-pha~e circuits emanating from the sub~tation are equipped with a line-mounted sensor module 22. Conventional circuit breaker3 26 are lnterposad in each circuit between it~
respective connection to the common bu~ phaqe and the a~ociated sen~or module~ 22.
In one embodiment each ~ensor module i~ programmed to tranqmit data in a 4.5 millisec burqt at ~ay the po~itive zero cro~ing of the voltage waveform for each pha~e o~ a circuit. Data transmis~ion~ are repeated at ~ay every 7th cycle. On the ~ame tran~mlssion frequency other circuit modules tran~mit on the 9th, 13th, 17th ¢ycle et¢. To a¢commodate larger number o~ circuits and 1 qec data re~re~h interval~, alternate circuit module~
oould be made to tran~mit on a ~econd frequency in a 4.5 :mllli-~ec. bur~t with respect to the negativa voltage ~, . _ .. --~: .. .. , .. , ., .. , .. ,,,,,, . _, . , . .. ._ _ _ , .... _ . __ _ __ .. , . ,,.. _ . . _ .. , ._.. , _ _ _ _ ___, _~ _ _ _ __ g_ -, :
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~,~;d3~35~ 5 zero cros~ing with repetition rates a3 above. Thi~ i~
done for all circuit~ tied to a given bus. For separate bu~e~ wlthin a ~tation additional ~requencie~ are u~ed, but, ~ith the same ~ynchronization and data burst cont~ol.
As described later in more detail, in a second conPiguration each of ~odules 22 includes means for both receiving and tran~mitting ~ignal~, a~ well a3 means ~or RenBing the value~ of various parameters a~o¢iated with the re~pective conductor upon which the ~ensor i9 mounted. Althou~h other type~ of communication~ link~
~ay be utilized, the invention i~ de~cribed hereln a~
compri~ing RF transmitting and receiving mean~ in each of ~ensors 22 and in a ~ingle ground station 29 in control house 28. Tran~mit and receive antennae o~ the . . .
ground station communication equipment are schematically indloated at 30 and 32, respectively. Corresponding communication equipment of the sen or~ iq shown and de~aribed later. A11 sen~or~ tranJmit data on a ~ingle frequsnoy chaanel for reception by antenna 32; ~i~nal~
are tran~m~tted by the ground ~tation ~rom antenna 30 on a second frequency channel ~or reeeption ~y the ~ensor receivers. For example, the system may employ a 950 MHz FM ~uplink" (from the ground ~tation to the ~ensor module ) and a 928 MHz FM "downlink.~
Each o~ modules 22 i~ equipped to mea3ure the value of voltage, current and pha~e angls of its ::

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~ ~5~5 associated conductor and may, if desired, be further equipped to measure other parameters such as frequency, conductor temperature, ambient temperature, conductor vibrations, etc.
In the second communication approach described for the sensor modules employing Time Division Multiple Acce6s, measurements of all parameters are made simultaneously by all modules 22 in the system at predetermined times establi~hed by a timing signal transmitted from the ground station and recelved by the modules. The timing signal further establi~he6 "time slots" in which data from each of the modules 22 i6 trans~itted in a predetermined sequence for reception at the ground station.
Sensor modùle electronics include a microprocessor, RAM, I10, and timer components, as disclosed in U.S. Patent No. 4,689,752. The sampled values of the monitored parameters are dlgitized, stored in RAM, and communicated to the ground station during the established time interval as a burst vf signals.~ The ground station includes~a microprocessor zo to which signals received from ~odules 22 are supplied for further~proce~sing, such as calculation of total circuit and/or substation kilowatts, kilowatt hours, kilovar~, ~etc. The data is then co~municated to a central data receiving and control facility br a data Iink schematically indica$ed at 34, such a6 radio, land sdl~C.
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through the present invention; details of construction and operation appear in tha balance of the disclosure.
A~ illustrated in Figure 2, modules 22 may be mounted upon energized, overhead conductor6, 6uch as that indicated at 35, easily and quickly by means of so-called ''hot stick'! 36 manipulated by an individual on the ground or in a bucket truck. Hot stick 36 includes a~ attachment tool 38 (to conventional hot-stick 36) which serve3 in the manner of an Allen wrench to engage portion6 of module 22 and efect opening and closing movement of two, hinged or pivot~d connected fiections of the module to permit mounting upon the conductor. One of may poæsible mechanical embodiments of the mounting means, details of ~hich orm no part of the pre6ent invention, may be found in U.S.
Patent No. 4,689,752.
Figures 3 and 4 illustrate the configuratlon of the sensor module'~ exterior and interior, re~pectively.
As shown in Figure 3, the module contains two lower sections 40 and two covers or upper sections 42, held together , by bolts (not shown) pa6sing through the covers into threads in the lower casting sections 40. An insulating ga6ket separates the uppe;r 42 and lower 40 housing sections so as not to form a short circuit loop ~: ~

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~urrounding the Rogow~ki coil 88 and the hinged power pick-of~ core90 whlch extend around the toru~ Ln the upper and lower 3ection~ re~pectively. Ea¢h lower ~ection 40 i9 provided with a top hub 44 and a bottom hub 46, supported by relative7y open ~poke~ 48, Figure 4. The ~en~or housing, generally indicated at 50, i~
Yecured to a clampin~ jaw3 a3~embly 52 by the open radial ~poke~ 48. The diameter of the internal opening oP the a3~embly dictated by neoprene type hub in~erts 47, i~ variable and i~ selected for each ~pecific power line oonduotor ~lze. The a~embly diameter can b~
oho~en to aooommodate di~erent power cables ~orm 0.5"
to 2~" in diameter. An R.F. impedanoe matching network 54, mounted near a~embly 52 i8 ¢onnected via coaxial cable part~ 56 to a ~hielded tranqmitter and eleotronic~
~hown generally at 58 in~ide module 22. Similar oonnection~ are made between the receiving antenna 60, if u~ed, and oommunications board 61 in~ide module 22 for the alternative embodiment employing the time ~ynchronized TDMA communications teahniqueO Also shown in Figure 3 i a ~ragment of hot-~tick tool ~6 with Allen wrench portion 38 extending into hole 62 Ln module .
22. The hot-stick i~ turned in one dire¢tion to cau~e the hingedtpivoted seetions of the module to open so ~: : that it can be placed over a conductor. Turning the : hot-~t~ck in the opposite direction cau~es the module to ; close over the oonductor and clamp onto it tlghtly. The .. . . _ . _ _ _ . . _ .. _ .. _ _ .. : .. .. , . .. , _ .. . _ .. . .. .. . ., . _ _ _ . . _ _ .. . _ ... .. _ ~ 13-.

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tool 36 can then be removed by imply pulling it away.
Rein~ertion and turning in the oppo~ike direction will open the module and allow it to be removed ~rom the tran~miq~lon line. This placement/removal feature provides great ~lexibility in locating the module~ ln the tran3mi~ion ~y~tem.
Further illustrated in Figure 3 are metallized pla~tio, tubular rod~ 64 and 66 which extend from ~en~or housing 50 and which terminate in metallized plastic ~phere~ 68 and 70, re~pectively. The tubes and ~pheres are drawn at reduced ~cale ~or illustrative purpose~.
The tubular rod~ 64 and 66 are attaohed to the ca~t aluminum sensor housing 50 by threaded in~ert~ 72 and 74, re~pectively. The tubular rod~ 64 and 66 with ~phereq 6~ and 70 provide an increa~e in the e~ective ~urrace area o~ the toroidal shaped ~en~or hou~ing 50 ~h~ch enhance3 the electrostatio charglng capac~ty o~
the present invention, Solar photovolaic cell~ embedded on the sur~ace o~ the tubular rod~ and ~phere~ can alYo be used, if required J to further augment the charging energy when line current i~ below the thre~hold for eleotromagnetic powering o~ the circuitry. An elsotrical connection between ~urface area~ i~ ensured by dlrect oontact between the metalliz~d rod~ 64 and 66 and th~ metal sensor hou~ing 50. In addit~on to the previously described element~, module 22 i~ equipped wlth CPU proces~or board 76, RAM 78, PROM board 80 and .. ,.. : , ~ ., ,,_-- . , . . _ .. __, __ . , , . . ,, . , ., _.. __ _ ,, .. _ _., . .. _ _ .. __,_ ,_ , .. , __ . .
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~ ~35~;1~;i optionally, electronically eraseable E2-PROM board 82.
For maxlmum packing density, multi-tiered circuit board~
are u~ed inside shielded compartments. Care i3 taken to avoid any 60Hz 3hort circuit loop~. Address bu~ 84 and data bu~ 86 interconnect the ¢ircuit oards, Power to operate the ~ensor module electronic~ is normally derived from windings on a laminated iron core which ~urround~ the conductor. The core i excited by the power line conduotor current forming the ~ingle turn primary and the power 3upply winding~ 134 form the ~econdary coll~ o~ the power ~upply transformer. The core and winding are shown diagramatically in latar Figures, and are divided into two -qections ~or mounting in the two hinged/pivoted connected ~ections o~ the toroidal hou~ing. Fragments of the upper portion~ of the two section~ of the iron core, both indicated by reference numeral 88, are ~hown in the broken-away portions at the bottom o~ the housing. ~hen module 22 mounted on the conductor, the pole faces of the two ~ection~ of core 88 muqt cIose with a minlmum controlled air gap and protected again~t corro~ion. For thi3 purpo~e, moisture-proof recess 90 i~ provided around one pole ~ace, and plastic hroud 92 urround~ and extend~

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outwardly ~rom the other pole face Por mating engagement with rece~ 90 in the clo3ed position of the module.

Module 22 is shown in cro~ ~ection in Figure 4.

Temperatura probe~, such as that indicated at 96, extend ~ .

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- :, ~ ~ ~5~5 from contacting relation with the conductor to electrical connectlon~ wLthin hou~ing 50 ln order to generate ~ignals commen~urate with the temperature of the conductor. Similarly, ambient air temperature in the vicinity o~ the conductor i9 meaaured by probe 98, enclo~ed in a white 3hroud 100 which protects the probe from both direct ~olar expo~ure and heat generated by the conductor. Opening3 102 permit air to flow freely over probe 98 and al~o en~ure dra~nage of conden~ation.
Both probe~ 96 and 98 are thermally in~ulated ~rom hou~ing 50 to prevent the latter ~rom effecting the ~en3ed value~.
Current flow through the conductor i~ mea~ured by Rogow3ki coil 104, which extends around the interior of hou~ing 50 in side-by-side relation with an array o~
rechargeable batteries 106. Coil 104 and batteries 106 ara held in place within sections 42 of the hou~ing by hold-down clamp3 108 and 110, re~pectively. Elements of the data ~en~ing, receiving and tran~mitting electronic3 are indicated generally by reference numeral 112 within hou~ing 50. The hub as~embly includes outer ring 11~, inner ring 116 inqulated therefrom by oxide~~llm layer 118, oonductive rub~er insert 120 ~elected in acoordance with the diameter o~ the condu¢tor, and optional synthetic rubber end hub cap~ 122 providing a moisture ~eal at each end o~ the hub where environmental oondition~ requireO Alternatively, the in~ulated oxide ~ s~
film ~unction may be provided between the hub 44 and rlng 114.
The ~ensor module electronics are shown in their overall con~iguration ln Figure 5. They comprise a power supply 124, 3ignal processing, ~ampling, ~torage and control electronics 126 9 the various parameter ~en~ors indicated by box 128, back-up energy ~torage and electro~tatic and/electromagnetic charging electronics 130.
The center tap 132 o~ the power pick-o~ ooils 134 and 134', surrounding core sections 88 and 88', re~pectively, i~ connected to metallic hou~ing 50 o~
sensor module 22, whlch in turn i3 connected through a capacitor provided by in~ulated outer and inner hub rings 114 and 116 to the power conductor via the conductlng insert 120. The regulated power supply 124 provides regulated -5 volts to the eleotronic~ 126 via lead 136, 136' and an additional~ swltcbed 12 volt~ ~or tran3mitter and recei~er 138 via lead 140. Electronic~
126 provides a transmitter aontrol ~ignal on line 139 to :cvntrol the power suppIy to the transmitter, as well a r~eceiver 141 in ~ystem~ wherein the sensor module~ also ~nclude a receiver, a~ de~cribed later. Sen~or~ 128 provlde analog ~ignals on lines indicatsd at 142 to electronic~ 126.
The schematic electrical circuit diagram of the power supply 124 and back up energy 3torage 130 is ~hown ,.

in Figure 6. The power back up ~ystem includes a rechargeable energy ~ource 3uch a~ previou31y ~entioned batterie~ 106, voltage and current monitoring circuitry provided a3 previously de3cribed~ and battery ~loat charglng circuitry 144. Without the apparatus of the present invention, mea~urement of tran~mi~sion line parameter3 wa~ not po~ible below a line current threshold o~ approximately 15 ampere~. Below this thre~hold level, the inductive power ~rom line current iq insufficient to operate the ~en~or module electronic~
and tranqmittar unle~s the power core cro~-qectional area were 3ignificantly inereased and therefore made much too heavy fo~ hot-~tick in~tallation on live tran~mi~sion line3~ Power ~upply ~4~ is shown ~ith it~
ma30r functlonal elements. During typical operation, I.e. with line current above the minimum ehre~hold value, power i~ derived through electromagnetic lnduction u~ing th~ magnetic ~leld generated a~ a result o~ current flowing through conductor 12. The hinged iron ~ore 88, with power pick-o~f coil3 134 providing the ~econdary, and the line conductor formin~ the slngle turn prlmary of a power transformer, supplie~ all internal power~to the sensor module. Winding 134 is connected to bridge rectifier 148 to pro~ide unregulated DG po~er. Protection again~t power ~urges i~ provided by a GEMOV deYioe 150. The output of recti~ier 148 is supplied to DC`regulator 152 which ~upplie~ the DC

._ . ~ . , ... , ._ .. , .. : . ., .. . .. . .. _ .. ; :.. .. . .. __. __ _ . , . _ . _. _ ., .. _ . _ __ ~ _ _ . .

~ 5 voltage~ required by sen~or module electronic~ on lines 136, 136' and 1liO. Capacitor 156 i9 connected between the regulator and the controller/clock circuitry 158.
As previou~ly de3cribed, current in the conductor i~ measured by Rogow~ki coil 104. Current thre~hold ~en~or 170, comprising operational amplifier 172 and re~istor 176 i~ fed current I on line 16~ from the Rogow~ki coil. The m~asured current thre~hold reference i~ 3et through re~i~tor 176, and i~ determined by the require~ent~ of the ~en~or module, e.g. 15 amperes.
Current I on line 166 i~ ~upplied to thre~hold comparator/detector 170 comprising amplifier 172 and resi~tor 174 whi¢h will detect current value3 above the thre~hold value a3 ~upplied through re~i3tor 176.
Comparator/detector 170 provide~ an above~below thre~hold indl¢ating si~nal on line 178 to the controller/clock 158.
Above the threshold current value, power i~
~upplied by electromagnetic 1nduction through power ~upply 1460 Belo~ the thre3hold value, power i~
~upplied to the sen~or module by rechargeable batteries 106. The 3tatu~ o~ the oonductor current (i.e.
abo~e~below thre3hold) 19 ~upplied to battery controIlericlock circuitry 158 by comparator/detector 170 on line 178. When the below-thre~hold condition i~
s~ensed, the controller 158 will enable DC power from ba~tery 106 to be supplied to regulator 152 on line 180.
.

:, __ __ ._ _ .. , ,_, .. . . _ . .... ... .... .. _ _ _ . .... . .
_ .~ .... .

: .

The DC voltage level3 required by the module electronic~
are thereby provided by the battery. When the conductor current reache3 the threshold level, controller 158 will allow ~loat charging o~ battery 106 and ~ensor module power i9 o~ce again supplied directly by power supply 146. For period~ of operat10n at zero current, with line ~oltage pre~ent 9 exceeding a pre~et (through PROM) duration the frequency of the transmi~ion bur~t~ is reduced to con~erve battery energy. I~, during ~u~tained period~ o~ zero current on the conductor, khe battery voltage ~all~ below a predetermined ~a~e value controller 158 will discontinue power ~upplied by battery 106 and prevent any additional drain. Further zero curren5 operation will be po~ible only a~ter the line current exceed~ the thre~hold ~etting and the battery i float or trickle charged.
The means o~ the pre~ent inventLon for measuring the voltage on the oonductor ~ illustrated in Figure 7.
Included in such mean~ are in~ulation of the housln¢
from the conductor, ~or example, the hub element~ of the module, i,e,, metal outer and inner ring~ 114 and 116, re3pectively, may be electrically ~nsulated ~rom one another by oxide ~ layer 118, indicated in Figure 7 a a capacitor9 and ¢onductive, re~ilient insert 120, all previously described in connection with Figure 4.
An inte~rator, indicated generally at 182, con~isting of operational amplifi-r 184 and galn con~rol feedback ~ - : 20 s capaaitor 186, ha~ on0 input connected through resistor 187 and capaaitor 188 to inner rlng 116, and the other to the outer skin of houslng 50 of module 22. The low input impedan¢e of operational amplifier 184 cau~es the charging current to flow from the high voltage conductor 10, through capacitor 188 and resi3tor 187, ~o the input o~ operational amplifier 184. The low impedance and high gain o~ amplifier 184 in~ures that the potential of housing 50 i8 eqsentially the same as that of conductor 10, i.e., the potential between housing 50 and ground is the potential between ground and conduotor 10. The in~ulating layer provided by metal oxide 118, cau~es the oharging currcnt to flow through amplifier 184 rather than directly to housing 50. Therefore, operatlonal amplifier 184 wl1l provide an AC output voltage exactly proportional to the current through the skin of sensor module 22 to ground, which is directly proportional to the high voltage between conductor 10 and ground. The dimenslon~ and material of the in~ulating layer 118 between inner and outer ring~ 114 and 116 are selected to pro~ide a capacitance value which would allow the ¢harging current of the highest ~requency voltage component to be measured to pa33 through to operational ampli~ier 184.
Capacitor 188 i~ relatively large, e.g~ 9 5~10 MFd, to block any DC signal~. Re~istor 187 i9 a current-limlting mean~ to protect again~t ~a~t rise-time , .. , _ _ ,_. _._ . . , .... ., .. ,._.. ., . ... ,, ,. _. _ _ .. _ .. _ ._ ... , _ . .. _ _ _ ... _ - .' ' ~
~' . , ~ .
. . . ~ - ~; ` ~

5~

surges. Diode 190 anc1 192 clamp the voltage acro~ re6istance-capacitance 187-188; 6imilarly, diodes 194 and 196 clamp the voltage acros~ the inputs of amplifier 184. Metal oxide surge 6uppre~or 198 protects ths circuit components again6t damage due to momentary transient6. The output signal repre~enting the Yoltage value is coupled, through electronics 126 (Fig. 5) to transmitter 138. The latter i~ coupled through RF shunting capacitor 200, to outer ring 114 which i8 connected directly to housing 50 and through capacitor formed at 118 to the conductor 10 at the RF tran6mi6sion frequency of 928 MHz. The components of the voltage mea6uring syste~ indi ated in Figure 7 are mounted within shielded (metal) enclosure 202 within hou6ing 50.
An alternate means for measuring voltage o~
conductor 10, disclosed in U.S. Patent No. 4,689,7$2 is illustrated in Figure 7A. Arcuate, electrically conductin~
plates or disc6 201 and 203 are attached to the e~terior of the metallic housing of module 22 with a thin layer ~20 of in~ulation between each plate and the housing surface, thereby providing a capacitance at each plate. In the drawing, Cdg and Ydg represent the capacitance and ~oltage~
re6pectively, between disc~ 201 and 203, which are connected by lead 205j and earth.~ Cdh representg the capacitance between thc discs and the module hou6ing, which is electrically sd/~ Z2-. ~ . .

:``~ :' ' : "

:
~ ' ` : ~,. -. ' :: .

connected to and thu~ at the potentlal of conductor 10.
High impedance amplifier 207 measure~ the voltage between the di~c~ and hou~lng (Vdh), which i~
proportional to the voltage between the di~c~ and earth (YdC), since the circuit i~ configured a~ a voltage divider. Tha input and feedback lmpedance of the amplifier are repre ented by Z; and Z~, respectively.
The mea~ured voltage YO between the output oP high impedance ampli~ler 207 and ground potential i3 proportional to the voltage acro~ the discs and hou~ing Vdh. Thi~ means of voltage measurement doe~ not provide the level of accuracy o~ the Figure 7 system, but i~
les~ expen~ive and may be acceptable for some applioations.
From the ~oregolng, it is apparent that the invention provides a ~en~or module, adapted for --hot-~tick mounting on an energized power conductor, ¢apable o~ measuring voltage a~ well a~ ourrent on the power conduotor (and other parameters, when de~ired).
~y providing current and voltage zero-cro~sing detection, the phase angle~ and ~requency may al~o be determined, thereby permitting quantitie~ ~ueh a~ watts and watt-hour ,: etc~ (in any desired comblnation o~
parameters) to be derived. The module electronio~ may be operated by power taken directly from the oonductor upon which ~he module l~ mounted or, when current on an energized conductor ~alls:below a predetermined ~ _ _ _ . _ _ . _ . _ _ . . _ . _ , _ , _ . _ . , . _ _ . _ _ _ . _ _ . . _ _ _ _ _ _ _ _ . _ _ . . _ . _ _ _ . . . . . . _ _ _ . . .
_ _ _ . _ _ _ . . _ . _ _ _ . _ _ _ _ . . . . _ _ _ . _ _ _ . . _ _ _ _ _ _ _ . _ _ _ _ _ _ _ _ . _ . _ _ _ _ _ _ _ . . . _ . _ _ _ . _ _ _ _ . . _ .
,.

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' ~ , . ' `' ' ' .:

:
' s~

thre~hold ~alue (including zero current condition~), by back-up power means independent of the conductor. The parameter values are transmitted from the modules to a ground station and system~ which may be employed for transmitting signals in a ti~e-6ynchronized manner from modules sensing the parameters on each phase of a three phase circuit, or rom all circuits of an entire ~ubstation will now be described.
Referring now to Figure 8, current and voltage on the conductor at a predetermined point in time are 6ens~d 6imultaneously by Rogow~ki coil 104 and housing S0, respectively, in the manner previously described.
Rogowski coil 104 is connected to input amplifier 220 through current range select resistors 222. The voltage ensor is connected through capacitor 188 to lo~ impedance ; operational amplifier 184 with feedback capacitor 186, aæ previously de~cribed, to provide an output ~ignal in pha~e with the line~to-neutral voltage. A novel means for improving the accuracy of voltage reading6 by compensating 20~ for the effect6 of adjacent, energized conductors i~ described in Canadian Patent No. 1,257,90~ of the present inventor.
Additional ampli~iers 6uch as that indicated at 230 are provided or mea6urement o additional parameter~, ~uch a6 conductor temperature, ambient temperature, conductor vibration~, etc. The output of ~ d/jc ~ -24-:~, '~

' ' , .
~: .

~ .

s~

each of the parameter-mea~uring amplifier~ i3 connected through multiplexer 231 for comparison with the output of digital/analog converter mean~ 232, which receives an input from voltage reference 234, at comparator 236, under the control of digital computer 238. The latter may be, Por example, a Motorola~ CMOS 6805 microproce330r having I~O, RAM and timer component3. Programmable read only memory 24~ i~ connected to the computer CPU for ~toring the program. Current and voltage zero cros~ing detection i~ provided by ampliPier~ 242 and 244, respectivelyJ each having one lnput connected to the output of the re~pective current and voltage mea~uring ampli~ier~, and the other input connected to ground, The output~ oP both zero cro~sing detector~ are connected directly to microproce~or 238 for phase measurement.
In addltion to providing She signal3 nece~sary for ~ea~urement oP phase angle and frequency (which i3 the inver~e of the time between 3uccessive po~itive going zero cro~ings) the ~ignalq from voltage zero cro~ing de~eo'cor 244 may be u~ed f`or synchronization of data tran~mission~ by transmitter 138 without requlring a reoeiver in the sen~or module and a transmitter at the ground station. ~eferring So Figure 9, the voltages on each pha e o~ a total of ~ive 3 phase circult~ are indicated wlth re pect to time. Trans~i~sions from each o~ the three individual ~en~or modules o~ ¢ircuit 1 (one : ~T~-~ l ..
' -25- l . .
; ~ .
' : .

~, ' ' .

s mounted on the conductor of each pha~e) are made, ~or example, within ~.5 milli~econd (or le~) burst~ Ma11, Mb11, MCl1 following each positive-going zero-cro~ing o~ the voltage on the aqsociated conductor at a fir~t 3elected frequency f1. That i~9 a coded me~age in the form oY a bur~t of slgnal~ indicative of the parameter~
mea~ured at that tlme may be tran~mitted by the tran~mitter of the module on phase A durlng time interval Mal1; the mes~age~ from the module~ mounted on the conductors of phases B and C are tran3mitted during time3 Mbl1 and MC11, re~pectively. Thi~ approach takes advantage o~ the fact that zero cros~ings of ad~acent phase~ o~ a 3-phase ¢irouit are speaced wt_120 apart.
Thu3, a complete data tran~mi~slon ~rom all three pha~e~
i9 completed withln one full cycle. 8y tran mitting the mes~age~ in a time span le~ than that between zero cros~ings o~ ~ucoe~3ive pha3e~ there will never be a problem with overlapping or inter~ering transmis~ion~
from more than one module at a time. Messages may be transmitted, for example, every se~enth cycla, leaving ample time ~or data colleotion and proce~ing between transmi~sion~. The tran~mit burst control si~nals are communicated from microproce~sor 238 to tran~mitter 138 via line 242.
::
When there are ~everal aircuit~ connected to a iven bu~ at a substatlon, tran3mi~10n~ may be ~ynchronized to prevent overlap by proper spacing o~ ¦

~ __ `_ ~__ ~ _ __ _ ` _ ___ _ _ _ _ _ _ _ _ _ ___ _ _ ___ _ _ _: _ _ _ _ _ _ _ _ _ __` _ ___ __ __ ___ _ _ _ __ _ _ _ _ _ __, _ _ __ ' _ _ ___ _ _ _ _ ___ _ . _ .. _ . _ ._ _ ._. _ _ _ . _ .. ___. _ . __ _ _ __ ~ -26~

~ .
~ ' .

~' :

;6~5 transmission~ and/or ~election of broadcast frequencies.
For example, tran~mis3ions from the modules o~ circuit 2 ma~ be initiated by the negaSive-going zero cro~sings on a second frequency, thus permitting transmissions overlapped in time with those ~rom the modules of circuit 1. The first message ~rom phase A of circuit 2 i~ transmitted during time Ma21, and those from phases B
and C during times Mb21 and MC21, respectively, Tran~mission3 may be made on the first frequen¢y from other circuits during the periods when the module~ of ~ircuit 1 are not tran~mitting. Circuit 3, ~or example, 1 may transmlt on the first frequency at times Ma31, Mb31 and Mo31 every eleventh cycle. The ~econd me~ages from the circuit 1 ~odule~ are tran3mitted at time~ Ma12, Mb12 and M¢12; arter the seventh cycle.
If tran~mi3sions Prom the three moduleQ of each circuit are completed ~ithin one ~ull cycle (as ~ould be the case for ~ucce~sive 4.5 millisecond tran~missions, .
sin¢e a ~ull oycle take~ 16.7 milliseconds at 60 ~z) then transmi3~ion from each cir¢uit would be spaced by a ; ~ number o~ cycle3 at least equal to the number of circu~t~. However, Ln order to in~ure that tran~mis~ion~ do not o~erlap a~ter temporary oircuit lntarruption~, whioh may occur at random, diPferent number~ of cycle spacings between tran~mis~ion~ should be cho~en for the olrcuits and no two numbers may have a ~I common denominator. For example, tran~missions from 5 ' :

cirouit~ on a ~ingle frequency could be ~paced by 7,11,13,17 and 19 cycles re pectively. Thu~, if it i~
important to receive data from each circuit wlth a high repitition rate, the number of broadcast frequen¢ie3 would be increased; on the other hand, if economy o~
frequency ~pectrum i~ more critical, trans~ ion~ would be ~paced more widely. It ~hould be noted, however, that as many a~ 10 circuit~ (30 module~) could tran~mit on a ~ingle ~requency with the data being updated every second. Thi~ approach does not require Recelving antenna 60, Receiver module 141, demodulator 250, CRC check module 252 and ~ynchronization pul~e code detector 254.
The~e module~ are deleted ~or thi~ mode o~ communication to the ground station.
Re~erring a~ain to Figure 8, a tran~ceiver ~ystem i~ ~hown whlch permits time qynchronized, 3equential data tran~ml~ion from a relatively largc number o~
module~, e.s., all ~odule~ nece~sary ~or monitorlng an entire substatioh suoh a3 that oP Figure 1, ko a single ground statlon on a ~ingle broadca~t ~requency. The zero cro~sin6 detectors previou~ly de~eribed for controlling the timlng o~ tran~mi~ions from the three modules~o~ one cirouit may al~o be uqed to provide basic ~ynchronization with TDMA coded timing ~ignal~
tran~mitted ~rom the ground ~tation and received at the -~; module by reeeiver 141. Each module i9 a~igned an identi~ying number which i3 ~elected initially through _.. ~, . ., .... .. ~ , . . . .. ... . ..... ... , .. ., . .. ,, .. . , .. . . . ., .. .. ._, . _, ., .. . .. ,.. , .
_ ., , .. , . , __ _ .. __ ._ _ _ _ , _,_ . ._ __ _ ' -28--~ ~ .

' ' ' . ' `
- '~
, ~8~;6~5 module 244. The digitized data representing the parameter values i~ as6embled into appropriate me~6ages, encoded in Manchester code by encoder 246 and supplied to transmitter 138 via line 248 for tran6mis6ion in assigned time slots designated by TDMA data burst control signals received .by receiver 141. The timing signals from the ground station are pas~ed on from receiver 141 to demodulator 250 (which can be part of the receiver 141~. The demodulated TDMA
signal contains information on the assigned time ~lot for transmis6ion by the particular sensor module. The signal is passed through CRC check module 252, for error detection and the pulse code is detected by module 2549 providing the microprocessor with information to ~ontrol the transmitter burst timing.
A block diagram of the ground station electronics u6ed at a sub~tation to receive tran6missions from all sen~or modules which perform the monitoring function, and proces6ing the signals recei~ed from such modules, i~ shown in Figure 10. A more detailed description is found in the Canadian Patent No. 1,257,902. When 6ensor modoles 2Z include self-contained control of transmission timing, the ground ~tation requires only recei~er mcans ~:~ (i.e., the modules requi:re no receiver and the ground station requires no transmitter). If, on the other hand, timing of transmission by the reSpeCtiYe modules is controlled ~ : to take place in : ~ 6d/jc -29-.: .
.: , .
:, ~; ' ' ;'' .' ' a~signed time ~lot~, in the manner previously mentioned, a transmitter iq provided at the ground ~tation and a receiver in each module. In either ca~e, the Manche~ter coded signal3 tran~mitted by the individual ~en~or moduleq are received through antenna 32 at recelver 256, pa~sed through ~erial port 258 of the communication board and C~C error check module 260 to CPU 262 through the data bu~r An I/O interface i3 provided for receiving external ~lgnals ~or implementing the Yunctlon3 o~ a conventional remote terminal ~ubstation unit, a3 indicated by the labeled blocks connected to CPU 262. Keyboard interface 264 i~ connected to CPU 262 ~or local control o~ parameter3 to be di~played on a 3ingle line alpha numeric di~play device 266. CPU 262 i3 al90 proYided with an RS 232 port 268 for loading and unloading per~onality tablea, or ~or a man-machine inter~ace u~ng a portable microcomputer~ ~uch a~ an IBM-XT or a COMPAQ. CPU 262 i~ provided in the u~ual manner with RAM 270, PROM 272 and Electronically Eraseable PROM 274, the latter being u~ed to di3play the scale ~actors and personality tables for the senYor -modules through RS 232 inter~aoe 268. The mioro-code ~: ~ for claoulatin~ the various output parametrer~ ig ~tored ~: : in PROM 272.

In addition to the data received ~rom sensor module~ 22, the co~bined remote terminal unit i3 equipped to reeeive direct9 hard-wired input~ ~rom 4T~ ~k '' - ' ' - .

'' ' ~ ~ . ., 3561.~;

conditioned, con~entional current and potential transformers 276 and 278, re6pectively. Analog signal6 proportional to the input current and voltage are fed to conditioning amplifiers 280, ~ample-and-hold circuitr~ 282 and thence to multiplexer 284 in a manner similar to the processing of analog signal6 in the sen60r modules, as previously described. A/D converter 286 and analog metering control board 288 transfer the digitized signals to CPU 262 where the data i6 proces6ed in a manner similar to the ~ensor module data~
The foregoing description of ground station electronics is amplified to ~ome extent in previou61y mentioned Canadian Patent No. 1,257,902 and includes all element6 required for receiving and processing signal~
transmitted by $he various sen60r modules. When timing of 6uch tran6mi~sions Is to be controlled by coded ~ignal~
indicatiDg as6igned time slots to each module, the ground station further includes time divi6ion multiple access (TDMA) me~sage synchro~ization signals from CPU 262, and conne~ted through pulse code modulator 2~Z to transmitter 294. The signals a~igning tran6mission time6 to the variou~ modules are then tran Mitted from the ground station Yia antenna 30 and received at the modules by receiving antenna 60 provided for 6uch purpo~e.
:
A direct comparison between substation monitoring as conventionally performed by hard-wired ~urrent and : ~"

~clljc -31-.' ' ' ' ' " . . .
.
; ~ ' ' ' ,, .. ' ' ' ` ~2 ~

potential tran3former~, and by the approach of the pre~ent invention i~ provided by Figure~ 11A and 11B, The conductor~ o~ each phase o~ a ~ingle circuit are indicated in Figure 11A by re~erence numeral~ 300, 301 and 3027 and in Figure 11B by numeral~ 300', 301', and 302', it being understood that the number o~ circuit~
and conductor3 would be dependent on the ~ize of the qtation. Under prior technology it ha~ been nece~ary to deenergize the circuits to in~tall new current and potential tran~formers for an overhead line. Such tran_formerq require ma~sive and co~tly porcelain buqhings, ~upport ~tructure3 and concrete ~oundation The~e pri~ary trans~ormers~ located in the ~ub~tation yard, mu3t then be connected to auxiliary transformers ¦ in a ¢ontrol house, which in ~urn are connected through te3t swit¢hes to di~crete tran~ducers ~or each quantity to be mea~ured. Transducer~ are connected through terminal blocks to a 3eparate, remote terminal unit (RT~
- Aecording to the teaohing~ o~ the pre~ent ~ . i invention, ~en~or module~ 22 are mounted upon each pha~e o~ the circuit and mea~ure current, voltage and pha3e angle in the manner de~cribed. The module~ may be ~ ~ mounted~directly upon energized conductor~, without I interruption of power. Sequential tran~mi~ion o~ data .
bur~t~ ~rom all modules at the ~ub3tatlon i9 controlled by either of the two di~clo3ed method , i~e., by ,: _ . __. , . ... . _ . , . ~ , _ . _ , ~_ .. . .. . . . .. , . . . . . _, _ . .. . . . .. .. ._ _ . .
~- 32 ~ Z1~35~i~5 ~ynchronization with voltage zero cro~.~ing~ and bur3ting data to the ground ~tat1on after a pre-~elected number of cycles have elap~ed ~or each module, or by providing a ground tran~mitter and a receiver in each module for coded time-synchronization 3ignal~. Signals indicating the sen~ed parameters on each phaqe of all circuit~ at the qub~tation are received and proce3sed at a ~ngle remote termlnal interPace and the ~ame microprocessor i9 u3ed to perform conventional alarm, ~tatus, sequence o~-event~, select-before-operate, other analog mon~toring, and pul3e accumulator funct~on~ o~ a conventional Remote Terminal Unit, i.e., the ground station act3 a~ a combined Remote Terminal Unit ~CRTU).
It i~ thu~ apparent that the pre~ent invention pro~ides a comple~e monitoring system which i~ ~uperior ---in performance and ~lexibility to conYentional ~y~tem9 while, at the 3ame time, being vastly smaller9 lighter, less co~tly. and more convenient to install~ remove, repair, etc. The compari~on is more dramatic when it is noted that all of t~e bulky and expensive equipment lndicated in Figure 11A must be ~uplioated in it3 entirety for every circuit monitored at a :ub~tation, wh~le only the ~enqor modules are duplicated (one ~or each condu~tor) ln Figure 11B regardless o~ the number o~ eircuits. That i~, only one CRTU, having a size essentially the same as that of the RTU o~ the con~entional ~ystem, i3 required in the pre~ent system, .. ~ .~. . . . ... . .... . _ ........ ... .. ; . :~ .. .... .... ... _. .. _ _ _ _.. _ .. ._.. __ . . .. . . . .___ ... _ _ .
.. _ .. _ . _ _._ `

.

' ,, thereby totally eliminating all the measurement tran~formers, test Ywitche~, transducer~, terminal block~, hard wiring and ~upporting structures required for every circuit in conventional ~ystems. By way of comparison, a sen~or module could have a weight of les~
than 20 pounds, while t'ne corre~ponding prior art equipmsnt would welgh several thousand pounds.

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Claims (28)

1. A system for monitoring a plurality of parameters associated with each of a plurality of energized electrical power conductors, one of said parameters being conductor voltage, on power system circuits operable over a load range between predetermined minimum and maximum conductor currents in either direction for complete installation and removal while said conductors are energized, said system comprising:
(a) a plurality of sensor modules each having a metallic housing, one of said modules being mounted upon each of said energized conductors, said housing being conductively isolated from said conductor at least for frequencies below the highest frequency of conductor voltage to be measured, whereby the surface of said housing continuously collects the charging current due to the electrostatic field associated with said conductor;
(b) means connected between said conductor and said housing for measurement of conductor voltage from said charging current;
(c) means contained within said housing for continuously sensing the current through said conductor over said entire load range;
(d) means carried by each of said modules for establishing the phase relationship between said sensed values of conductor voltage and conductor current;

(e) means carried by each of said modules for identifying, processing and storing said sensed values of conductor voltage and conductor current and said established phase relationship;
(f) means carried by each of said modules for transmitting a sequence of encoded signals commensurate with each of said sensed values and including said established phase relationship and sensor module identification; and (g) means remote from said modules for receiving said signals from each of said plurality of sensor modules, decoding said signals and calculating voltage, current and power factor of each of said conductors.

2. The invention according to Claim 1 wherein said remote means includes means for calculating power and energy quantities from said readings of voltage, current and phase over said entire load range.

3. The invention according to Claim 1 and further including means for measuring the frequency of voltage and current on said conductors.

4. The invention according to Claim 1 and further including means for sensing parameters other than voltage, current and phase.

5. The invention according to Claim 1 wherein said conductor voltage and current contain harmonic and transient components and said remote means includes means for calculating the harmonic and transient components of voltage, current and power.

6. The invention according to Claim 1 wherein said housing is conductively isolated from said conductor by a relatively thin layer of insulation interposed therebetween.

7. The invention according to Claim 1 wherein said housing is conductively isolated from said conductor by a capacitance having a value providing a relatively high impedance at said frequencies below the highest frequency of conductor voltage to be measured and appearing as a short circuit between said housing and conductor above said highest frequency, thereby permitting said charging current to flow through said conductor voltage measurement means at said frequencies below the highest frequency of conductor voltage to be measured.

8. The invention according to Claim 1 wherein said means for establishing phase relationship include means for detecting zero crossings of conductor current and voltage, and said data transmitting means includes means to transmit a message of predetermined duration in synchronization with said voltage zero crossings.

9. The invention according to Claim 1 and further including energy storage means carried by said sensor modules for powering said transmitting means when current flow through the associated power conductor is below a predetermined threshold value.

10. The invention according to claim 9 and further including means for charging said energy storage means from the electromagnetic field associated with said conductor.

11. The invention according to Claim 9 and further including means for charging said energy storage means from the electromagnetic and electrostatic field associated with said conductor and said metallic housing.

12. The invention according to Claim 11 and further including means carried by each of said sensor modules for generating an indicating signal when current flow through the associated conductor is below said threshold value.

13. The invention according to Claim 12 wherein said transmitting means includes an RF transmitter and means for regulating the frequency of transmissions.

14. The invention according to Claim 13 and further including means responsive to the presence of said indicating signal for a predetermined, continuous period of time to reduce said frequency of transmissions.

15. The invention according to Claim 14 and further including means carried by each of said modules for sensing voltage on said associated power conductor with no current in said associated power conductor and for providing a signal indicating the no current condition.

16. The invention according to Claim 15 including means for electrostatically charging said battery when no current is flowing through said power conductor and data is not being transmitted from said device.

17. The invention according to Claim 1 and further including means carried by each of said sensor modules for deriving electrical power from the electromagnetic field associated with current flow through said power conductor for powering all sensor module electronics.

18. The invention according to Claim 1 and further including conductor temperature measurement means carried by each of said modules and including a temperature probe having a portion in direct contact with the associated conductor to measure the temperature thereof and means for avoiding any influence on said temperature measurement due to heat from said sensor module and solar sources.

19. The invention according to Claim 18 and further including means carried by each of said sensor modules for measuring ambient temperature of the air immediately adjacent the associated conductor.

20. The invention according to Claim 19 wherein said avoiding means comprise a protective shroud surrounding at least a portion of said temperature probe.

21. A system for monitoring a plurality of parameters associated with each of a plurality of energized electrical power conductors for complete installation and removal while said conductors are energized, said system comprising:
(a) a plurality of sensor modules, one of said modules being mounted upon each of said energized conductors;
(b) means carried by each of said modules for sensing values of a plurality of parameters of the associated power conductor;

(c) means carried by each of said modules for identifying, processing and storing said sensed values;
(d) means carried by each of said modules for periodically transmitting a sequence of encoded signals in data bursts of predetermined duration from each of said plurality of sensor modules commensurate with each of said sensed values;
(e) means carried by each of said modules for controlling the starting times of said data bursts by said transmitting means of each of said modules to avoid simultaneous transmission, with consequent data collisions, by any two of said modules; and (f) means remote from said modules for receiving said signals from each of said plurality of modules and decoding said signals to provide said parameter values at said remote means.

22. The invention according to Claim 21 wherein said controlling means of each of said modules establishes said starting times for beginning transmission by said transmitting means in relation to a reference point on the voltage waveform which is chosen to be the same for all modules on conductors connected to the same phase of a common three-phase bus.

23. The invention according to Claim 22 wherein said reference point is the zero crossing of the voltage on one phase of said common bus, said times for beginning transmissions by the modules on adjacent phases of each three-phase circuit is displaced by the successive zero crossings of each phase, and said duration of transmission by each module is less than the time between successive zero crossings of adjacent phases.

24. The invention according to Claim 23 wherein predetermined times for successive transmissions from each module are an integral multiple of elapsed voltage cycles.

25. The invention according to Claim 24 wherein said integral multiple is different for each of said modules and does not have a common denominator with said integral multiple of any other module.

26. The invention according to Claim 21 and further including an RF transmitter and antenna for transmitting signals on a second frequency from a location remote from said modules, and an RF receiver and antenna carried by each of said modules for receiving signals at said second frequency.

27. The invention according to Claim 26 wherein said signals transmitted on said second frequency are encoded to provide an address unique to each of said modules including its assigned time slot for transmitting said sequence of signals on said first frequency.

28. The invention according to Claim 21 wherein said controlling means includes means for detecting zero crossings of conductor current and voltage, said data transmitting means includes means to transmit a message of predetermined duration in synchronization with said voltage zero crossing.