CA1073050A - Electrical network voltage control device - Google Patents
Electrical network voltage control deviceInfo
- Publication number
- CA1073050A CA1073050A CA245,413A CA245413A CA1073050A CA 1073050 A CA1073050 A CA 1073050A CA 245413 A CA245413 A CA 245413A CA 1073050 A CA1073050 A CA 1073050A
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- Prior art keywords
- electrical network
- winding
- circuit
- phase
- transformer
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Abstract
ABSTRACT OF THE DISCLOSURE
The invention provides a voltage control arrangement for an electrical network comprising: a transformer provided with first and second windings, said first winding being adapted to be connected in series with said electrical network; a feedback circuit having an input adapted to be connected to a phase line of said electrical network, and an output for providing a control signal in response to a voltage parameter in said electrical network; and a variable impedance circuit having a pair of main terminals, and a control terminal for electrically varying the impedance of said circuit, said variable impedance circuit comprising a capacitor and an inductor connected in parallel, at least one of said inductor and said capacitor having an electrically variable impedance; the control terminal of said variable impedance circuit being connected to the output of said feedback unit, and the main terminals of said variable impedance circuit being connected in series with the second winding of said transformer and a voltage source, whereby said control signal varies the impedance of said impedance circuit and thereby induces a correcting voltage in said transformer in response to deviations of said voltage parameters.
The invention provides a voltage control arrangement for an electrical network comprising: a transformer provided with first and second windings, said first winding being adapted to be connected in series with said electrical network; a feedback circuit having an input adapted to be connected to a phase line of said electrical network, and an output for providing a control signal in response to a voltage parameter in said electrical network; and a variable impedance circuit having a pair of main terminals, and a control terminal for electrically varying the impedance of said circuit, said variable impedance circuit comprising a capacitor and an inductor connected in parallel, at least one of said inductor and said capacitor having an electrically variable impedance; the control terminal of said variable impedance circuit being connected to the output of said feedback unit, and the main terminals of said variable impedance circuit being connected in series with the second winding of said transformer and a voltage source, whereby said control signal varies the impedance of said impedance circuit and thereby induces a correcting voltage in said transformer in response to deviations of said voltage parameters.
Description
~ 3050 The pr~sent lnvention relates to transmission and ~is- -tribution of electrical energy and, more specifically, to automatic voltage control devices, and it can be applied in high-voltage electrical networks.
Phase and amplitude deviations of voltage from a rated value are inevitable in electrical energy systems resulting from the presence of impedances in said systems. Said voltage deviations impair working conditions of electric power consumers, impair economic factors of an energy system and create higher risks for accidents. Hence, voltage must be stabilized. Even more so, sometimes voltage must be not just stabilized, but also changed in accordance with a certain law.
Known in the art is a voltage control device (Prudominskiy V.V. "Transformers", issue 25, Moscow, 1974, pages 20-31), comprising a transformer, one of its windings being connected in series with the phase of an electrical network, the second winding of said transformer being connected into a voltage control circuit, a feedback unit and a voltage control means, comprising an adjusting transformer, an adjusting winding of which is provided with taps admitting of stepped changing of coefficient of transformation, a current limiter, switching elements and a operating mechanism. On a deviation of voltage in the network from a prescribed value, the operating mechanism is brought into use and, said mechanism, by the action on the switching elements, provides for connecting with an appropriate tap of the adjusting winding. Said connection re-~ :
Phase and amplitude deviations of voltage from a rated value are inevitable in electrical energy systems resulting from the presence of impedances in said systems. Said voltage deviations impair working conditions of electric power consumers, impair economic factors of an energy system and create higher risks for accidents. Hence, voltage must be stabilized. Even more so, sometimes voltage must be not just stabilized, but also changed in accordance with a certain law.
Known in the art is a voltage control device (Prudominskiy V.V. "Transformers", issue 25, Moscow, 1974, pages 20-31), comprising a transformer, one of its windings being connected in series with the phase of an electrical network, the second winding of said transformer being connected into a voltage control circuit, a feedback unit and a voltage control means, comprising an adjusting transformer, an adjusting winding of which is provided with taps admitting of stepped changing of coefficient of transformation, a current limiter, switching elements and a operating mechanism. On a deviation of voltage in the network from a prescribed value, the operating mechanism is brought into use and, said mechanism, by the action on the switching elements, provides for connecting with an appropriate tap of the adjusting winding. Said connection re-~ :
-2- 7~
, i~ 10730S0 sults in a changed voltage across the second winding of the transformer, which winding is connected into the voltage control circuit. The value of current in a shorted circuit, which is formed as the switching elements are switched over, is limited by the current limiter.
One of the constructional features of the device is a large number of switchings ranging from 10,000 to 100,000 a year. -This places more stringent requirements upon reliability of operation of voltage control devices. Besides, the step-wise mode of changing voltage impedes effecting most efficient operating conditions of the electrical network, while an ~-insufficiently quick acting of said devices in operation makes it impossible to use them for emergency control purposes.
The process of switching of switching elements is accompanied by electric arcing, which results in rapid wearing of the contacts. ~ `-It is an object of the present invention to provide a voltage control device ensuring efficient operating conditions `
of an electrical network. -;
Yet another object of the invention is to provide a ~-device having a wide range of control.
Still another object of the invention is to attain a faster acting voltage control device.
Yet another object of the present invention is to ;
increase life expectancy of the voltage control device.
A further object of the invention is to provide high operation reliability of the voltage control device.
,~ . . . " .
.... . . .
-~`` lU730~0 ~ ccordingly, the present invention provides a voltage control arrangement for an electrical network comprising:
a transformer provided with first and second windings, said first winding being adapted to be connected in series with said electrical network; a feedback circuit having an input adapted to be connected to a phase line of said electrical network, and an output for providing a control signal in response to a voltage parameter in said electrical network;
and a variable impedance circuit having a pair of main terminals, and a control terminal for electrically varying the impedance of said circuit, said variable impedance circuit comprising a capacitor and an inductor connected in parallel, at least one of said inductor and said capacitor having an electrically variable impedance; the control terminal of said variahle impedance circuit heing connected to the output of said feedback unit, and the main terminals of said variable impedance circuit being connected in series with the second winding of said transformer and a voltage source, whereby said control signal varies the impedance of said impedance circuit and thereby induces a correcting voltage in said transformer in response to deviations of said voltage parameter.
It is advisable to ins~rt the electrical circuit between a neutral conductor of the electrical network and one end of the second winding of the transformer, the other end of said winding being connected to the phase of the electrical network.
In accordance with another embodiment of the present invention, the electrical circuit is inserted between the phase of the electrical network and one end of the second winding of the transformer, the other end of the second winding of the transformer being connected to the neutral conductor -4- .
of the electrical network.
It is expedient, in a voltage control device for a three-phase electrical network, each phase of said network comprising a transformer, a feedback unit and a voltage control means, to "star-connect" the circuit of all three phases and ; :
.
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to conn~ct each electrical circuit in series with the second winding of the transformer, the other end o~ said winding being connected to one of the phases of the electrical network.
In accordance wit~ another embodiment of the present invention in a voltage control device ~or a three-phase electrical network the second windings of transformers m~y be star-connected, each of the electrical circuits being inserted between a respective seoond windin~ of the tran~-former and one of the pha~es of the electrioal network.
In accordance with ~till another embodiment of the present invention, in a voltage control device for a three-phase electri¢al network, an electrical circuit and a se¢ond wind-inB of a transformer of all the three phases, said winding and said transformer being connected in series, may be delta-connected, eaoh ape~ of 3aid delta-oonnection being connected to one of the phases of the eleotrical network.
The proposed devioe provides for a oontinuous and wide-ranging voltage control, which feature makes it possible to ¢arry out the most efficient operating c ~ 0~9 of the electrical network~ Owin~ to absense of~swibohing devioes the speed o~ volbage oontrol oonsiderably inoreases, whioh feature makes it po3sible to u~e said devioe ~or emergenoy control under emergenoy conditions o~ operation.
Owing to the fa¢t, that arcing in the devi¢e i9 excluded, the reliability and life expectancy of the device are suf-fioiently in¢reased.
~j .
10'73~)S0 The invention will now be described in more detail, by way of example only, with reference to the accompanying drawings, wherein:
Fig. 1 shows an electrical circuit of variable impedance which is known per se, but which is employed in a voltage control device according to the invention;
Fig. 2 shows a functional diagram of one embodiment of a voltage control device for a single-phase electrical network including an electrical circuit shown in Fig. l;
Fig. 3 shows a functional diagram of a voltage control device for a single-phase electrical network in another embodiment, according to the invention;
Fig. 4 shows a functional diagram of a voltage control device, for a three-phase electrical circuit, in another embodiment according to the invention;
Fig~ 5 shows a functional diagram of a voltage control device, for a three-phase electrical network in still another embodiment according to the invention;
Fig. 6 shows a functional diagram of a voltage control device for a three-phase electrical network in yet another embodiment according to the invention;
Fig. 7 shows a functional diagram of a voltage control device, for a three-phase electrical network in a further -~ embodiment according to the invention.
An electrical circuit I (Fig. 1) of variable impedance ~, comprises a capacitor 2 and a variable inductor 3 which are connected in parallel with one another. The inductor 3 is provided with a control terminal 3' for electrically changing the value of its inductance. Conveniently, this is achieved by electrically changing the degree of magnetization of the inductor core.
A voltage control device for a single-phase network _ i~730~o comprises an electrical circuit 1 (Fig. 2 and 3), similar to that described in Fig. 1, a feedback unit 4, a transformer havlng windings 5 and 6. The feedback unit 4 derives a signal dependent value of the parameter, to be controlled and may be the same as the feedback unit described in the Porudansky article referred to above. The winding 5 is connected in series with a phase "A" of the electrical network. In accordance with one of the embodiments of the invention, one main terminal 1" of the circuit 1 (Fig. 2) is connected to a neutral conductor of the electrical network, and the other main terminal 1' of said circuit 1 is connected to one end of the winding 6, whereas the other end of the winding 6 is connected to the phase "A" of the power line to be controlled. The input of the unit 4 is connected to the phase "A", and its output is connected to the control terminal ; 3' of the cixcuit 1.
In accordance with another embodiment, one end of the winding 6 tFig. 3) is connected to the neutral conductor, the other end being connected to one main terminal of the circuit 1. The other main terminal of the circuit 1 is connected to the phase "A". The input of the unit 4 is connected to the phase "A", the output of said unit being connected to the control terminal of circuit 1~
The voltage control device for a three-phase electrical network comrpises variable impedance circuits lA, lB, lC
(Fig. 4, 5, 6, 7), feedback units 4A~ 4B~ 4C and transformers having windings 7 and 8, g and 10, 11 and 12. The winding 7 is connected in series with a phase "B", the winding 11 being connected to a ' 10730~U
phase "C". The inlet of the unit ~A is connected to the phase "A", the outlet of said unit 4A being connected to the circuit IA, the inlet of the unit 4B is connected to the phase "B", the outlet of said unit 4B being connected to the circuit IB, the inlet of the unit 4C is connected to the phase "C", the outlet of said unit 4C being connected to the circuit Ic. According to one embodiment, one end of the winding 8 (Fig. 4) is connected to the phase "A", the other end of said winding 8 being connected to one main terminal of the circuit IA, one end of the winding I0 is connected to thephase "B", the other end of said winding being connected to one main terminal of the circuit IB, one end of the winding 12 is connected to the phase "C", the other end of said winding 12 being connected to one main terminal of the circuit Ic. The free other main terminals of the circuits IA, IB and IC are star-connected.
In accordance with another embodiment in a voltage control device for a three-phase electrical network, one main terminal of the circuit IA (Fig. 5) is connected to the phase "A" of the electrical network, the other main terminal being connected to one end of the winding 8, one main terminal of the circuit IB is connected to the phase "B", the other main terminal being connected to one end o~ the winding 10, one main terminal of the circuit IC is connected to the phase "C", the other main terminal being connected to one end of the winding 12. The free ends of the windings 8, 10 and 12 are star-connected.
In accordance with still another embodiment in a voltage control device for a three-phase electrical network, _~_ _ ~0'~30~0 the circuit IA (Fig. 6) is connected in series with the winding 8, the circuit IB is connected in series with the winding 10, the circuit IC is connected in series with the winding 12. A free end of the winding 8 is connected to a main terminal of the circuit IB and to the phase "A". A free end of the winding 10 is connected to a main terminal of the circuit IC and the phase "B". A free end of the winding 12 is connected to a main terminal of the circuit I and the phase "C", forming thereby a delta-connection.
The device operates as follows.
The variahle impedance circuit I (Fig. I) has an impedance that can be changed by changing the inductance of the inductor 3. However, it is also possible to change the capacitance of the capacitor 3 instead of or as well as the inductance of the inductor 3.
A controlled reactor serves in the device according to the invention as the variable inductor 3, in which reactor ` the inductance variation is attained by means of magnetizing the magnetic circuit. Therewith, the limits of the range ~ 20 of the voltage control are determined by the limits of variation of the value of inductivity of the controlled ; reactor. The variation of impedance of the circuit I ranges from infinity, when the circuit I i9 tuned to resonance, to a certain value, which is determined by the parameters of the capacitor 2 and of the inductor 3.
At fixed voltage in a single-phase electrical network the electrical circuit I (Fig. 2) is tuned to resonance and is of in-. , .;
:, 'I .~3G~
.i _g_ ,, '-` 1()~30~0 finite impedance. The circuit of the winding 6 of the transfor-mer is free from electric current, the electromotive force in said circuit being of zero value and is not transformed into the winding 5.
As the voltage in the network deviates from that of a predetermined value, a signal comming from the feedback unit 4 is delivered to the electrical circuit I, which signal acts on the inductor 3 (Fig. I), changing the value thereof, and, there-by changing the impedance value of the circuit I. Resultingly, an electric current is generated in the winding 6 (Fig. 2) of ~ -the transformer, said current inducing e.m.f. in the winding 2.
This e.m.f. is transformed into the winding 5. Thus an addition~
al e.m.f. is introduced into the electric network.
Depending on conditions of operation of the electrical network the method of connection of the windings 5 and 6 of the transformer may be changed to an inverse one, resulting in chang-ing the sign of the additional e.m.f.
The value of the additional e.m.f. is determined -deviation of the network voltage, whereas the limits of the range of deviation of said e.m.f. depend on the ratio between the minimum value of resistance of the circuit I and the resistance of the winding 6 of the transformer.
The operation of the voltage control device on bringing the electrical circuit I into use, as shown in Fig. 3, also follows the above description.
.
~ 30S~3 In a three_phase electrical network, the voltage of the phase~ "A", "B", "C" (~ig.4) being o~ a fi~ed value, ths circuits IA, IB and IC are al~o tuned to re~ona~ce a~d are of i~inite re~istance. ~he cirouit~ o~ the windings 8, I0 12 are free ~ro~
electric curre~t and the e~m.~. in ~aid wi~ding~ i~ of æero value. That is wh~ the additio~al e.m.f. in each o~ the windin4s 7~ 9~and II are Also of zero value.
At voitase deviation i~ the phase "~" o~ the eleotrlcal netw~rk a 9ignal comming ~rom the ~ollow-up unit 4A is delivered into the electrical oircu~t IA~ which ~ignal cha~ges the value of inductivity of the vhriable lnductivit~ 3 (Fig~ I), re~ulting in changing of the re~i~tance of the circuit I. Therewith~ a~ eleet-ri¢ current i~ generated in the winding 8 (Fig. 4)~ ~aid curre~t inducin~ e.m.~ in ~id w*nding 8. The induced e.m.~ trans-~ormed into the winding 7 and is iatroduced into the phase 11`~ as an additional e.m.~.
~ t,voltage deviation in the pha~,e "B" a ~ignal comming ~rom : the follo~-up unit ~ i~ delivered into the circuit IB~ ~he cha~g-i~ o~ the re~i~ba~ce of the circuit IB re~ults ~n ~enerat~Rg of e~ectria cu~re~t in the windin~ I0 a~d i~ indu¢i~g a3 e.m,~.
ln oe~d wlndlng I0. Sald e,m.~. is tra~oformed into the windin6 9 e~d sL~ i~Ltrodu~ed into the pha~e "B" ~ additional e.m.~.
oltage deviation iin the ph~se "C" a 8ignal comin~ ~rom ,j.,.~, ~, the~ ~llow~ u~t 4a l~ delivered to thè circuit I~. ~he cha ~
of the ~ o~ the circuit IC resulbs in generation ~f an electri¢ current in the windin~ I2 and in i~ducin~ a~ e~m~f.
` ` 1073~0 i~ said winding I2. Said e.m.f. iæ trans~ormed i~to the windi~g II and iæ introduced into the phase ItC" a~ a~ additio~al e.m.r, ~ he device operates i~ an a~alogous way at voltage deviating from a predetermined value thereof in two or thr~e phase~ at a ti~
~ ith other connection aiagr~ms o~ ~ig,5~ Fig~6 a~d Fig,7 the volta~e oontrol device o~erate~ following the above deæcrip-tio~.
The volt~ge control de~ice, embodime~t~ of which aIe show~
in Figure~ 2, 3~ 4, 5~ 6, ~nd 7 ca~ provide ~or both,~uo ~d phase voltage control.
~ I~ need be, bo increase the network voltage ~ ~odu~ the vector of the additional e~m.f. mu~t coincide with that o~ the co~trol~ed yo~tage~ ~hereas ~hould the need arise to decrees the ~ Ql voltuge ~o~h~5, the vector of the additional e.m.f, mu3t be o~
the oppo~ite direction to that o~ the controlled voltage.
~ or phase voltage ¢o~trol of the net~ork the ~ector of the additional e.-~. must be directed at a~ angle to that oi the ~: controlled voltage. The value of a~ angle between the vector of the additional e~m.~. a~d that o~ the controlled voltage l~
de~ined ~o~ eaoh ~peci~ic insta~oe de~endln~ on ~arameber~ o~ a given energy ~ystem. ~he value of ~aid angle depe~dA o~ a method o~ connecbing the electric c~rcuit~ and the ~indin~s of traus~or-mers to the p~a~es oi the electrical net~ork~ as well as of a gra;m o~ mubual ¢on~ection~ of 8aid ele¢tr~¢al cirouit~ and winding6 of bhe tra~rormers.
,~ . ` . . . - . . .
~. ~ . , . . `
, . `,~ : . :
~ loq3aso By u~i~g difierent dia~ram~ of con~ection of the above ele¢-trical circuit and windi~gs o~ the tran~ormer to the electrical network and by using various way of mutual con~ection thereof~ a vector o~ the additional e.m.~. directed to that o~ the control-led voltago at an a~le o~ 0, 30, 60~ 90~ 120, 150, 180, 210~ 240~ 270~ 300~ 330 can be derived.
~ he described device is characteri~ed b~ high reliabilit~
a~d inorea~ed li~e expecta~cy, The ufie of the device accordl~g to the inve~tio~ sub~t~ntially improves eco~omic ~a¢tors of energy ~ystem.
~ 1 3 ,... ..
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, i~ 10730S0 sults in a changed voltage across the second winding of the transformer, which winding is connected into the voltage control circuit. The value of current in a shorted circuit, which is formed as the switching elements are switched over, is limited by the current limiter.
One of the constructional features of the device is a large number of switchings ranging from 10,000 to 100,000 a year. -This places more stringent requirements upon reliability of operation of voltage control devices. Besides, the step-wise mode of changing voltage impedes effecting most efficient operating conditions of the electrical network, while an ~-insufficiently quick acting of said devices in operation makes it impossible to use them for emergency control purposes.
The process of switching of switching elements is accompanied by electric arcing, which results in rapid wearing of the contacts. ~ `-It is an object of the present invention to provide a voltage control device ensuring efficient operating conditions `
of an electrical network. -;
Yet another object of the invention is to provide a ~-device having a wide range of control.
Still another object of the invention is to attain a faster acting voltage control device.
Yet another object of the present invention is to ;
increase life expectancy of the voltage control device.
A further object of the invention is to provide high operation reliability of the voltage control device.
,~ . . . " .
.... . . .
-~`` lU730~0 ~ ccordingly, the present invention provides a voltage control arrangement for an electrical network comprising:
a transformer provided with first and second windings, said first winding being adapted to be connected in series with said electrical network; a feedback circuit having an input adapted to be connected to a phase line of said electrical network, and an output for providing a control signal in response to a voltage parameter in said electrical network;
and a variable impedance circuit having a pair of main terminals, and a control terminal for electrically varying the impedance of said circuit, said variable impedance circuit comprising a capacitor and an inductor connected in parallel, at least one of said inductor and said capacitor having an electrically variable impedance; the control terminal of said variahle impedance circuit heing connected to the output of said feedback unit, and the main terminals of said variable impedance circuit being connected in series with the second winding of said transformer and a voltage source, whereby said control signal varies the impedance of said impedance circuit and thereby induces a correcting voltage in said transformer in response to deviations of said voltage parameter.
It is advisable to ins~rt the electrical circuit between a neutral conductor of the electrical network and one end of the second winding of the transformer, the other end of said winding being connected to the phase of the electrical network.
In accordance with another embodiment of the present invention, the electrical circuit is inserted between the phase of the electrical network and one end of the second winding of the transformer, the other end of the second winding of the transformer being connected to the neutral conductor -4- .
of the electrical network.
It is expedient, in a voltage control device for a three-phase electrical network, each phase of said network comprising a transformer, a feedback unit and a voltage control means, to "star-connect" the circuit of all three phases and ; :
.
, '~ , ~ 20 :-.. .
, .
~ ~ .
`',`. ~
. ' .
,. ' ,1`
` ~ -4a-:,........ . . . ~ . . -,. . : -iV~30~
to conn~ct each electrical circuit in series with the second winding of the transformer, the other end o~ said winding being connected to one of the phases of the electrical network.
In accordance wit~ another embodiment of the present invention in a voltage control device ~or a three-phase electrical network the second windings of transformers m~y be star-connected, each of the electrical circuits being inserted between a respective seoond windin~ of the tran~-former and one of the pha~es of the electrioal network.
In accordance with ~till another embodiment of the present invention, in a voltage control device for a three-phase electri¢al network, an electrical circuit and a se¢ond wind-inB of a transformer of all the three phases, said winding and said transformer being connected in series, may be delta-connected, eaoh ape~ of 3aid delta-oonnection being connected to one of the phases of the eleotrical network.
The proposed devioe provides for a oontinuous and wide-ranging voltage control, which feature makes it possible to ¢arry out the most efficient operating c ~ 0~9 of the electrical network~ Owin~ to absense of~swibohing devioes the speed o~ volbage oontrol oonsiderably inoreases, whioh feature makes it po3sible to u~e said devioe ~or emergenoy control under emergenoy conditions o~ operation.
Owing to the fa¢t, that arcing in the devi¢e i9 excluded, the reliability and life expectancy of the device are suf-fioiently in¢reased.
~j .
10'73~)S0 The invention will now be described in more detail, by way of example only, with reference to the accompanying drawings, wherein:
Fig. 1 shows an electrical circuit of variable impedance which is known per se, but which is employed in a voltage control device according to the invention;
Fig. 2 shows a functional diagram of one embodiment of a voltage control device for a single-phase electrical network including an electrical circuit shown in Fig. l;
Fig. 3 shows a functional diagram of a voltage control device for a single-phase electrical network in another embodiment, according to the invention;
Fig. 4 shows a functional diagram of a voltage control device, for a three-phase electrical circuit, in another embodiment according to the invention;
Fig~ 5 shows a functional diagram of a voltage control device, for a three-phase electrical network in still another embodiment according to the invention;
Fig. 6 shows a functional diagram of a voltage control device for a three-phase electrical network in yet another embodiment according to the invention;
Fig. 7 shows a functional diagram of a voltage control device, for a three-phase electrical network in a further -~ embodiment according to the invention.
An electrical circuit I (Fig. 1) of variable impedance ~, comprises a capacitor 2 and a variable inductor 3 which are connected in parallel with one another. The inductor 3 is provided with a control terminal 3' for electrically changing the value of its inductance. Conveniently, this is achieved by electrically changing the degree of magnetization of the inductor core.
A voltage control device for a single-phase network _ i~730~o comprises an electrical circuit 1 (Fig. 2 and 3), similar to that described in Fig. 1, a feedback unit 4, a transformer havlng windings 5 and 6. The feedback unit 4 derives a signal dependent value of the parameter, to be controlled and may be the same as the feedback unit described in the Porudansky article referred to above. The winding 5 is connected in series with a phase "A" of the electrical network. In accordance with one of the embodiments of the invention, one main terminal 1" of the circuit 1 (Fig. 2) is connected to a neutral conductor of the electrical network, and the other main terminal 1' of said circuit 1 is connected to one end of the winding 6, whereas the other end of the winding 6 is connected to the phase "A" of the power line to be controlled. The input of the unit 4 is connected to the phase "A", and its output is connected to the control terminal ; 3' of the cixcuit 1.
In accordance with another embodiment, one end of the winding 6 tFig. 3) is connected to the neutral conductor, the other end being connected to one main terminal of the circuit 1. The other main terminal of the circuit 1 is connected to the phase "A". The input of the unit 4 is connected to the phase "A", the output of said unit being connected to the control terminal of circuit 1~
The voltage control device for a three-phase electrical network comrpises variable impedance circuits lA, lB, lC
(Fig. 4, 5, 6, 7), feedback units 4A~ 4B~ 4C and transformers having windings 7 and 8, g and 10, 11 and 12. The winding 7 is connected in series with a phase "B", the winding 11 being connected to a ' 10730~U
phase "C". The inlet of the unit ~A is connected to the phase "A", the outlet of said unit 4A being connected to the circuit IA, the inlet of the unit 4B is connected to the phase "B", the outlet of said unit 4B being connected to the circuit IB, the inlet of the unit 4C is connected to the phase "C", the outlet of said unit 4C being connected to the circuit Ic. According to one embodiment, one end of the winding 8 (Fig. 4) is connected to the phase "A", the other end of said winding 8 being connected to one main terminal of the circuit IA, one end of the winding I0 is connected to thephase "B", the other end of said winding being connected to one main terminal of the circuit IB, one end of the winding 12 is connected to the phase "C", the other end of said winding 12 being connected to one main terminal of the circuit Ic. The free other main terminals of the circuits IA, IB and IC are star-connected.
In accordance with another embodiment in a voltage control device for a three-phase electrical network, one main terminal of the circuit IA (Fig. 5) is connected to the phase "A" of the electrical network, the other main terminal being connected to one end of the winding 8, one main terminal of the circuit IB is connected to the phase "B", the other main terminal being connected to one end o~ the winding 10, one main terminal of the circuit IC is connected to the phase "C", the other main terminal being connected to one end of the winding 12. The free ends of the windings 8, 10 and 12 are star-connected.
In accordance with still another embodiment in a voltage control device for a three-phase electrical network, _~_ _ ~0'~30~0 the circuit IA (Fig. 6) is connected in series with the winding 8, the circuit IB is connected in series with the winding 10, the circuit IC is connected in series with the winding 12. A free end of the winding 8 is connected to a main terminal of the circuit IB and to the phase "A". A free end of the winding 10 is connected to a main terminal of the circuit IC and the phase "B". A free end of the winding 12 is connected to a main terminal of the circuit I and the phase "C", forming thereby a delta-connection.
The device operates as follows.
The variahle impedance circuit I (Fig. I) has an impedance that can be changed by changing the inductance of the inductor 3. However, it is also possible to change the capacitance of the capacitor 3 instead of or as well as the inductance of the inductor 3.
A controlled reactor serves in the device according to the invention as the variable inductor 3, in which reactor ` the inductance variation is attained by means of magnetizing the magnetic circuit. Therewith, the limits of the range ~ 20 of the voltage control are determined by the limits of variation of the value of inductivity of the controlled ; reactor. The variation of impedance of the circuit I ranges from infinity, when the circuit I i9 tuned to resonance, to a certain value, which is determined by the parameters of the capacitor 2 and of the inductor 3.
At fixed voltage in a single-phase electrical network the electrical circuit I (Fig. 2) is tuned to resonance and is of in-. , .;
:, 'I .~3G~
.i _g_ ,, '-` 1()~30~0 finite impedance. The circuit of the winding 6 of the transfor-mer is free from electric current, the electromotive force in said circuit being of zero value and is not transformed into the winding 5.
As the voltage in the network deviates from that of a predetermined value, a signal comming from the feedback unit 4 is delivered to the electrical circuit I, which signal acts on the inductor 3 (Fig. I), changing the value thereof, and, there-by changing the impedance value of the circuit I. Resultingly, an electric current is generated in the winding 6 (Fig. 2) of ~ -the transformer, said current inducing e.m.f. in the winding 2.
This e.m.f. is transformed into the winding 5. Thus an addition~
al e.m.f. is introduced into the electric network.
Depending on conditions of operation of the electrical network the method of connection of the windings 5 and 6 of the transformer may be changed to an inverse one, resulting in chang-ing the sign of the additional e.m.f.
The value of the additional e.m.f. is determined -deviation of the network voltage, whereas the limits of the range of deviation of said e.m.f. depend on the ratio between the minimum value of resistance of the circuit I and the resistance of the winding 6 of the transformer.
The operation of the voltage control device on bringing the electrical circuit I into use, as shown in Fig. 3, also follows the above description.
.
~ 30S~3 In a three_phase electrical network, the voltage of the phase~ "A", "B", "C" (~ig.4) being o~ a fi~ed value, ths circuits IA, IB and IC are al~o tuned to re~ona~ce a~d are of i~inite re~istance. ~he cirouit~ o~ the windings 8, I0 12 are free ~ro~
electric curre~t and the e~m.~. in ~aid wi~ding~ i~ of æero value. That is wh~ the additio~al e.m.f. in each o~ the windin4s 7~ 9~and II are Also of zero value.
At voitase deviation i~ the phase "~" o~ the eleotrlcal netw~rk a 9ignal comming ~rom the ~ollow-up unit 4A is delivered into the electrical oircu~t IA~ which ~ignal cha~ges the value of inductivity of the vhriable lnductivit~ 3 (Fig~ I), re~ulting in changing of the re~i~tance of the circuit I. Therewith~ a~ eleet-ri¢ current i~ generated in the winding 8 (Fig. 4)~ ~aid curre~t inducin~ e.m.~ in ~id w*nding 8. The induced e.m.~ trans-~ormed into the winding 7 and is iatroduced into the phase 11`~ as an additional e.m.~.
~ t,voltage deviation in the pha~,e "B" a ~ignal comming ~rom : the follo~-up unit ~ i~ delivered into the circuit IB~ ~he cha~g-i~ o~ the re~i~ba~ce of the circuit IB re~ults ~n ~enerat~Rg of e~ectria cu~re~t in the windin~ I0 a~d i~ indu¢i~g a3 e.m,~.
ln oe~d wlndlng I0. Sald e,m.~. is tra~oformed into the windin6 9 e~d sL~ i~Ltrodu~ed into the pha~e "B" ~ additional e.m.~.
oltage deviation iin the ph~se "C" a 8ignal comin~ ~rom ,j.,.~, ~, the~ ~llow~ u~t 4a l~ delivered to thè circuit I~. ~he cha ~
of the ~ o~ the circuit IC resulbs in generation ~f an electri¢ current in the windin~ I2 and in i~ducin~ a~ e~m~f.
` ` 1073~0 i~ said winding I2. Said e.m.f. iæ trans~ormed i~to the windi~g II and iæ introduced into the phase ItC" a~ a~ additio~al e.m.r, ~ he device operates i~ an a~alogous way at voltage deviating from a predetermined value thereof in two or thr~e phase~ at a ti~
~ ith other connection aiagr~ms o~ ~ig,5~ Fig~6 a~d Fig,7 the volta~e oontrol device o~erate~ following the above deæcrip-tio~.
The volt~ge control de~ice, embodime~t~ of which aIe show~
in Figure~ 2, 3~ 4, 5~ 6, ~nd 7 ca~ provide ~or both,~uo ~d phase voltage control.
~ I~ need be, bo increase the network voltage ~ ~odu~ the vector of the additional e~m.f. mu~t coincide with that o~ the co~trol~ed yo~tage~ ~hereas ~hould the need arise to decrees the ~ Ql voltuge ~o~h~5, the vector of the additional e.m.f, mu3t be o~
the oppo~ite direction to that o~ the controlled voltage.
~ or phase voltage ¢o~trol of the net~ork the ~ector of the additional e.-~. must be directed at a~ angle to that oi the ~: controlled voltage. The value of a~ angle between the vector of the additional e~m.~. a~d that o~ the controlled voltage l~
de~ined ~o~ eaoh ~peci~ic insta~oe de~endln~ on ~arameber~ o~ a given energy ~ystem. ~he value of ~aid angle depe~dA o~ a method o~ connecbing the electric c~rcuit~ and the ~indin~s of traus~or-mers to the p~a~es oi the electrical net~ork~ as well as of a gra;m o~ mubual ¢on~ection~ of 8aid ele¢tr~¢al cirouit~ and winding6 of bhe tra~rormers.
,~ . ` . . . - . . .
~. ~ . , . . `
, . `,~ : . :
~ loq3aso By u~i~g difierent dia~ram~ of con~ection of the above ele¢-trical circuit and windi~gs o~ the tran~ormer to the electrical network and by using various way of mutual con~ection thereof~ a vector o~ the additional e.m.~. directed to that o~ the control-led voltago at an a~le o~ 0, 30, 60~ 90~ 120, 150, 180, 210~ 240~ 270~ 300~ 330 can be derived.
~ he described device is characteri~ed b~ high reliabilit~
a~d inorea~ed li~e expecta~cy, The ufie of the device accordl~g to the inve~tio~ sub~t~ntially improves eco~omic ~a¢tors of energy ~ystem.
~ 1 3 ,... ..
.. ..
~.- - . . . . .
. . .
~ , - . - ~
. . .
. . .
- i
Claims (6)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A voltage control arrangement for an electrical network comprising: a transformer provided with first and second windings, said first winding being adapted to be connected in series with said electrical network; a feedback circuit having an input adapted to be connected to a phase line of said electrical network, and an output for providing a control signal in response to a voltage parameter in said electrical network; and a variable impedance circuit having a pair of main terminals, and a control terminal for electrically varying the impedance of said circuit, said variable impedance circuit comprising a capacitor and an inductor connected in parallel, at least one of said inductor and said capacitor having an electrically variable impedance; the control terminal of said variable impedance circuit being connected to the output of said feedback unit, and the main terminals of said variable impedance circuit being connected in series with the second winding of said transformer and a voltage source, whereby said control signal varies the impedance of said impedance circuit and thereby induces a correcting voltage in said transformer in response to deviations of said voltage parameter.
2. A device as claimed in claim 1, wherein said variable impedance circuit is inserted between a neutral conductor of the electrical network and one end of said second winding of the transformer, the other end of said second winding being connected to said electrical network to provide said voltage source.
3. A device as claimed in claim 1, wherein said variable impedance circuit is inserted between said electrical network and one end of said second winding of the transformer, the other end of said second winding of the transformer being connected to a neutral conductor of the electrical network.
4. A three-phase electrical network provided in each phase thereof with a voltage control arrangement as claimed in claim 1, and wherein the variable impedance circuits of all said three phases are star-connected, the electrical circuit of each phase being connected in series with the second winding of the transformer of that phase, the other end of each said second winding being connected to the respective phase of the electrical network.
5. A three-phase electrical network provided in each phase thereof with a voltage control device as claimed in claim 1, in which the second windings of the transformers of all said three phases are star-connected, and each of said variable impedance circuit is inserted between the second winding of each transformer and the respective phase of the electrical network.
6. A three-phase electrical network provided in each phase thereof with a voltage control device as claimed in claim 1, in which the variable impedance circuit and the second winding of the transformer of each of said three phases, said variable impedance circuit and said winding being mutually connected in series, are delta-connected, each apex of said delta-connection being connected to the respective phase of the electrical network.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA245,413A CA1073050A (en) | 1976-02-10 | 1976-02-10 | Electrical network voltage control device |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA245,413A CA1073050A (en) | 1976-02-10 | 1976-02-10 | Electrical network voltage control device |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1073050A true CA1073050A (en) | 1980-03-04 |
Family
ID=4105201
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA245,413A Expired CA1073050A (en) | 1976-02-10 | 1976-02-10 | Electrical network voltage control device |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1073050A (en) |
-
1976
- 1976-02-10 CA CA245,413A patent/CA1073050A/en not_active Expired
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