CN101593970A - A kind of method for compensating time-domain capacitive current for double-circuit line on same pole - Google Patents

Abstract

The present invention relates to circuit microcomputer pilot protection field, be specifically related to research field, further relate to a kind of method for compensating time-domain capacitive current for double-circuit line on same pole with bar double back transmission line pilot protection.The present invention is by setting up the alternate Electrostatic Coupling model of double-circuit line on same pole six, in time domain phase-splitting calculate compensation each relatively with alternate capacitance current.This method not only can compensate this loop line over the ground with alternate capacitance current; can also effectively compensate the capacitance current between two loop lines; can not only the compensate for steady state capacitance current, can also compensate the transient state capacitance current, improved the performance of current differential protection on the double-circuit line on same pole greatly.And this method is only used the electric parameters of this loop line, and need not to introduce the current information of other loop line, and the device wiring is simple, and amount of calculation is less, can directly be applied in the existing double-circuit line on same pole protective device.

Description

A kind of method for compensating time-domain capacitive current for double-circuit line on same pole

Technical field

The present invention relates to circuit microcomputer pilot protection field, be specifically related to research field, further relate to a kind of method for compensating time-domain capacitive current for double-circuit line on same pole with bar double back transmission line pilot protection.

Background technology

Transmission line is a force device maximum in the electric power system, also is the higher element of failure rate.Because its important function in transferring electric power and contacted system, its main protection are selected the pilot protection such as the widely used current differential protection of quick-action completely usually for use.And for super, ultra high voltage long-distance transmission line, capacitance current is very big, and this is the principal element that influences the current differential protection performance.

Influence the problem of current differential protection at capacitance current, mainly contain two kinds of solutions at present:

One, adopts the new protection philosophy that not influenced by capacitance current, these new protection philosophies need higher sample frequency usually, better instrument transformer progress of disease performance, perhaps communication port there is very high requirement, often be difficult in the existing protective device and use, because system is to the strict demand of protection reliability, new principle often needs could use in practice through after the repeated examinations; For example when adopting the Bergeron model, the influence of capacitance current is even with considering.And based on the sampling rate and the communication port that have protective device now, using has better approximate lumped parameter ∏ model to distributed parameter line, carries out the compensation of capacitance current, just can satisfy actual needs preferably, has therefore obtained extensive use.

Two, use the capacitance current compensation technique, improve the performance of existing current differential protection.As:

(1) utilize shunt reactor to compensate capacitance current.This method is subjected to the influence of shunt reactor operational mode, and is generally undercompensation, can only part compensate for steady state capacitance current.

(2) utilize the condenser current compensation algorithm to reduce the influence of capacitance current.This method is divided into stable state phasor penalty method and modulus time domain compensation method, and the former can only the compensate for steady state capacitance current, and the latter then can compensate the transient state capacitance current simultaneously.

Actual transmission line generally adopts shunt reactor to add the capacitance current backoff algorithm simultaneously, reduces the influence of capacitance current to line differential protection.General step is as follows: at first utilize the storage and the computing function of Microcomputer Protection, obtain the synchronizing current value at local terminal magnitude of voltage and two ends at protective device; Utilize the backoff algorithm that provides to carry out current compensation then; Finish the differential current protection at last.But because in this operating process, all at present backoff algorithms all only at single back line, can only compensate the alternate and capacitance current over the ground of single loop line.When being applied in the condenser current compensation method of single loop line on the double-circuit line on same pole, because of can't compensating the capacitance current between two loop lines, so compensation effect is limited, still can't reach desirable current differential protection performance.

Summary of the invention

The present invention will provide a kind of method for compensating time-domain capacitive current for double-circuit line on same pole, and is limited to overcome the compensation effect that prior art exists, and can't reach the weak point of desirable current differential protection performance.

In order to overcome the problem that prior art exists, the invention provides a kind of method for compensating time-domain capacitive current for double-circuit line on same pole, this method comprises following step:

(1) set up equivalent-circuit model: this model adopts static and the electromagnetic coupling effect between the alternate and line of ∏ type circuit equivalent double loop;

(2) determine the offset current of two side loops according to equivalent-circuit model:

Electric current after M side I loop line C compensates mutually is:

$i_{\mathrm{mC}}^{\&prime;}=i_{\mathrm{mC}}-\frac{{\mathrm{<figure-callout\; id="2"\; label="C\; s"\; filenames="A2009100230410009H1.png"\; state="\{\{state\}\}">C</figure-callout>}}_s}{2}\frac{{\mathrm{du}}_{\mathrm{mC}}}{\mathrm{dt}}-(\frac{C_m^{\&prime;}}{2}+\frac{C_m}{2})\frac{d(u_{\mathrm{mC}}-u_{\mathrm{mA}})}{\mathrm{dt}}-(\frac{C_m^{\&prime;}}{2}+\frac{C_m}{2})\frac{d(u_{\mathrm{mC}}-u_{\mathrm{mB}})}{\mathrm{dt}}$

$=i_{\mathrm{mC}}-\frac{C_s+3(C_m^{\&prime;}+C_m)}{2}\frac{{\mathrm{du}}_{\mathrm{mC}}}{\mathrm{dt}}+\frac{C_m^{\&prime;}+{\mathrm{<figure-callout\; id="2"\; label="C\; m"\; filenames="A2009100230410009H1.png"\; state="\{\{state\}\}">C</figure-callout>}}_m}{2}\frac{3{\mathrm{du}}_0}{\mathrm{dt}}$

$=i_{\mathrm{mC}}-\frac{{\mathrm{<figure-callout\; id="2"\; label="C\; L"\; filenames="A2009100230410009H1.png"\; state="\{\{state\}\}">C</figure-callout>}}_L}{2}\frac{{\mathrm{du}}_{\mathrm{mC}}}{\mathrm{dt}}+\frac{C_m^{\&prime;}+{\mathrm{<figure-callout\; id="2"\; label="C\; m"\; filenames="A2009100230410009H1.png"\; state="\{\{state\}\}">C</figure-callout>}}_m}{2}\frac{3{\mathrm{du}}_{m0}}{\mathrm{dt}}---\left(1\right)$

Electric current after N side I loop line C compensates mutually is:

$i_{\mathrm{nC}}^{\&prime;}=i_{\mathrm{nC}}-\frac{{\mathrm{<figure-callout\; id="2"\; label="C\; L"\; filenames="A2009100230410009H1.png"\; state="\{\{state\}\}">C</figure-callout>}}_L}{2}\frac{{\mathrm{du}}_{\mathrm{nC}}}{\mathrm{dt}}+\frac{C_m^{\&prime;}+{\mathrm{<figure-callout\; id="2"\; label="C\; m"\; filenames="A2009100230410009H1.png"\; state="\{\{state\}\}">C</figure-callout>}}_m}{2}\frac{3{\mathrm{du}}_{n0}}{\mathrm{dt}}---\left(2\right)$

In formula (1) and (2), C ' _m, C _mAnd C _sRepresent between line respectively, alternate and equivalent capacity over the ground, Z _sBe the equivalent self-impedance of this phase,

The equivalent electromotive force of representing electromagnetic coupled between alternate and line; C _L=C _s+ 3 (C ' _m+ C _m) be double loop line mould electric capacity, 3u _M0=u _MA+ u _MB+ u _MC, 3u _N0=u _NA+ u _NB+ u _NC, u _MA, u _MB, u _MCAnd u _NA, u _NB, u _NCBe respectively the three-phase voltage at circuit two ends.

Principle of the present invention is by setting up the alternate Electrostatic Coupling model of double-circuit line on same pole six, in time domain phase-splitting calculate compensation each relatively with alternate capacitance current.This compensation method only is decided by the line construction of double-circuit line on same pole, and is irrelevant with load current and fault current size.Therefore compare with existing resist technology, the present invention has the following advantages:

(1) method provided by the invention not only can compensate this loop line over the ground with alternate capacitance current; can also effectively compensate the capacitance current between two loop lines; can not only the compensate for steady state capacitance current; can also compensate the transient state capacitance current, improve the performance of current differential protection on the double-circuit line on same pole greatly.This method only need be used the electric parameters of this loop line, and need not to introduce the current information of other loop line, and the device wiring is simple, can directly be applied in the existing double-circuit line on same pole protective device.

(2) this method works in time-domain capacitive current, not only can compensate the stable state capacitance current of double-circuit line on same pole, can also compensate its transient state capacitance current;

(3) this method only uses the electric parameters of this loop line to do compensation operation, and amount of calculation is little, need not to use other loop line current information, has avoided the complicated wiring of protective device, when improving existing current differential protection sensitivity, has also strengthened the reliability of protection.

(4) method compensation effect of the present invention is good, can reach desirable current differential protection performance, and sensitivity and reliability all are significantly improved.

Description of drawings

Fig. 1 is the ∏ type equivalent circuit diagram of double-circuit line on same pole M side I loop line C phase;

Embodiment

Below in conjunction with the enforcement of inciting somebody to action in conjunction with the accompanying drawings and the inventor finishes, the present invention is described in further detail.

A kind of method for compensating time-domain capacitive current for double-circuit line on same pole provided by the invention comprises following step:

(1) set up equivalent-circuit model: this model adopts static and the electromagnetic coupling effect between the alternate and line of ∏ type circuit equivalent double loop;

(2) determine the offset current of two side loops according to equivalent-circuit model:

Electric current after M side I loop line C compensates mutually is:

$i_{\mathrm{mC}}^{\&prime;}=i_{\mathrm{mC}}-\frac{{\mathrm{<figure-callout\; id="2"\; label="C\; s"\; filenames="A2009100230410009H1.png"\; state="\{\{state\}\}">C</figure-callout>}}_s}{2}\frac{{\mathrm{du}}_{\mathrm{mC}}}{\mathrm{dt}}-(\frac{C_m^{\&prime;}}{2}+\frac{C_m}{2})\frac{d(u_{\mathrm{mC}}-u_{\mathrm{mA}})}{\mathrm{dt}}-(\frac{C_m^{\&prime;}}{2}+\frac{C_m}{2})\frac{d(u_{\mathrm{mC}}-u_{\mathrm{mB}})}{\mathrm{dt}}$

$=i_{\mathrm{mC}}-\frac{C_s+3(C_m^{\&prime;}+C_m)}{2}\frac{{\mathrm{du}}_{\mathrm{mC}}}{\mathrm{dt}}+\frac{C_m^{\&prime;}+{\mathrm{<figure-callout\; id="2"\; label="C\; m"\; filenames="A2009100230410009H1.png"\; state="\{\{state\}\}">C</figure-callout>}}_m}{2}\frac{3{\mathrm{du}}_0}{\mathrm{dt}}$

$=i_{\mathrm{mC}}-\frac{{\mathrm{<figure-callout\; id="2"\; label="C\; L"\; filenames="A2009100230410009H1.png"\; state="\{\{state\}\}">C</figure-callout>}}_L}{2}\frac{{\mathrm{du}}_{\mathrm{mC}}}{\mathrm{dt}}+\frac{C_m^{\&prime;}+{\mathrm{<figure-callout\; id="2"\; label="C\; m"\; filenames="A2009100230410009H1.png"\; state="\{\{state\}\}">C</figure-callout>}}_m}{2}\frac{3{\mathrm{du}}_{m0}}{\mathrm{dt}}---\left(1\right)$

Electric current after N side I loop line C compensates mutually is:

$i_{\mathrm{nC}}^{\&prime;}=i_{\mathrm{nC}}-\frac{{\mathrm{<figure-callout\; id="2"\; label="C\; L"\; filenames="A2009100230410009H1.png"\; state="\{\{state\}\}">C</figure-callout>}}_L}{2}\frac{{\mathrm{du}}_{\mathrm{nC}}}{\mathrm{dt}}+\frac{C_m^{\&prime;}+{\mathrm{<figure-callout\; id="2"\; label="C\; m"\; filenames="A2009100230410009H1.png"\; state="\{\{state\}\}">C</figure-callout>}}_m}{2}\frac{3{\mathrm{du}}_{n0}}{\mathrm{dt}}---\left(2\right)$

In formula (1) and (2), C ' _m, C _mAnd C _sRepresent between line respectively, alternate and equivalent capacity over the ground, Z _sBe the equivalent self-impedance of this phase,

The equivalent electromotive force of representing electromagnetic coupled between alternate and line; C _L=C _s+ 3 (C ' _m+ C _m) be double loop line mould electric capacity, 3u _M0=u _MA+ u _MB+ u _MC, 3u _N0=u _NA+ u _NB+ u _NC, u _MA, u _MB, u _MCAnd u _NA, u _NB, u _NCBe respectively the three-phase voltage at circuit two ends.

To provide concrete application example below:

One, at first utilizes the current transformer (TA) and the voltage transformer (TV) of this side of circuit, gather voltage and current signal, and obtain local terminal (is example with the m end) voltage sample value u by the forward path of Microcomputer Protection _Ma(i), u _Mb(i), u _Mc(i) ... u _Ma(i+N), u _Mb(i+N), u _Mc(i+N) ..., and home terminal current sampled value i _Ma(i), i _Mb(i), i _Mc(i) ... i _Ma(i+N), i _Mb(i+N), i _Mc(i+N) ... (annotate: i=0,, was delivered to the opposite end protective device and finishes synchronous the current information of local terminal again by special-purpose or multiplexing communication port corresponding to the initial moment of fault.For the situation of circuit two ends band shunt reactor, above-mentioned current sampling data should compensate the shunting of local terminal shunt reactor, and with the current i after the compensation " _Ma(i), i " _Mb(i), i " _Mc(i) ... i " _Ma(i+N), i " _Mb(i+N), i " _Mc(i+N) ... replace primary current sampled value i _Ma(i), i _Mb(i), i _Mc(i) ... i _Ma(i+N), i _Mb(i+N), i _Mc(i+N) ..., be delivered to the opposite end and carry out the follow-up condenser current compensation calculating and the calculating of current differential protection criterion.A is example mutually with the m end, and the method that specifically compensates the shunt reactor shunting is as follows: $i_{\mathrm{ma}}^{\&prime;\&prime;}\left(i\right)=i_{\mathrm{ma}}\left(i\right)-\underset{k=1}{\overset{i}{\mathrm{\&Sigma;}}}\frac{u_{\mathrm{ma}}\left(k\right)}{\stackrel{\&OverBar;}{L}}\&CenterDot;h.$ Wherein, h is a sampling time interval, and L is the inductance value of local terminal a phase circuit shunt reactor correspondence.

Widely used phase-splitting electric current phasor differential protection criterion has following form:

$I_{\mathrm{cd}}=|{\stackrel{\&CenterDot;}{I}}_m+{\stackrel{\&CenterDot;}{I}}_n|>I_0---\left(3\right)$

$K_{\mathrm{cd}}=\left|\frac{{\stackrel{\&CenterDot;}{I}}_{\mathrm{cd}}}{{\stackrel{\&CenterDot;}{I}}_{\mathrm{zd}}}\right|=\left|\frac{{\stackrel{\&CenterDot;}{I}}_m+{\stackrel{\&CenterDot;}{I}}_n}{{\stackrel{\&CenterDot;}{I}}_m-{\stackrel{\&CenterDot;}{I}}_n}\right|>K---\left(4\right)$

Wherein, Be differential current,

Be stalling current, K is the restraint coefficient setting value.

Utilize the storage and the computing function of Microcomputer Protection, obtain at protective device can carrying out next step after the synchronizing current value at local terminal magnitude of voltage and two ends.

Two, utilize method disclosed by the invention to make the double-circuit line on same pole condenser current compensation then

According to formula provided by the invention (1), (2), with each phase current sampling value i of circuit two ends _Ma(i), i _Mb(i), i _Mc(i) ... i _Ma(i+N), i _Mb(i+N), i _Mc(i+N) ... and i _Na(i), i _Nb(i), i _Nc(i) ... i _Na(i+N), i _Nb(i+N), i _Nc(i+N) ... carry out differential calculation respectively, the current i after obtaining respectively compensating mutually ' _Ma(i), i ' _Mb(i), i ' _Mc(i) ... i ' _Ma(i+N), i ' _Mb(i+N), i ' _Mc(i+N) ... and i ' _Na(i), i ' _Nb(i), i ' _Nc(i) ... i ' _Na(i+N), i ' _Nb(i+N), i ' _Nc(i+N)

Be example mutually with I loop line c below,, be implemented as follows referring to Fig. 1:

$i_{\mathrm{mc}}^{\&prime;}\left(i\right)=i_{\mathrm{mc}}\left(i\right)-\frac{{\mathrm{<figure-callout\; id="2"\; label="C\; L"\; filenames="A2009100230410009H1.png"\; state="\{\{state\}\}">C</figure-callout>}}_L}{2}\frac{{\mathrm{du}}_{\mathrm{mc}}}{\mathrm{dt}}\left(i\right)+\frac{C_m^{\&prime;}+{\mathrm{<figure-callout\; id="2"\; label="C\; m"\; filenames="A2009100230410009H1.png"\; state="\{\{state\}\}">C</figure-callout>}}_m}{2}\frac{3{\mathrm{du}}_{m0}}{\mathrm{dt}}\left(i\right)$ And $i_{\mathrm{nc}}^{\&prime;}\left(i\right)=i_{\mathrm{nc}}\left(i\right)-\frac{{\mathrm{<figure-callout\; id="2"\; label="C\; L"\; filenames="A2009100230410009H1.png"\; state="\{\{state\}\}">C</figure-callout>}}_L}{2}\frac{{\mathrm{du}}_{\mathrm{nc}}}{\mathrm{dt}}\left(i\right)+\frac{C_m^{\&prime;}+{\mathrm{<figure-callout\; id="2"\; label="C\; m"\; filenames="A2009100230410009H1.png"\; state="\{\{state\}\}">C</figure-callout>}}_m}{2}\frac{3{\mathrm{du}}_{n0}}{\mathrm{dt}}\left(i\right)$ Differential calculation adopts two dot center's difference to replace in the formula, promptly $\frac{{\mathrm{du}}_{m0}}{\mathrm{dt}}\left(i\right)=\frac{u_{m0}(i+1)-u_{m0}(i-1)}{2h},$ $\frac{{\mathrm{du}}_{n0}}{\mathrm{dt}}\left(i\right)=\frac{u_{n0}(i+1)-u_{n0}(i-1)}{2h},$ $\frac{{\mathrm{du}}_{\mathrm{mc}}}{\mathrm{dt}}\left(i\right)=\frac{u_{\mathrm{mc}}(i+1)-u_{\mathrm{mc}}(i-1)}{2h},$ $\frac{{\mathrm{du}}_{\mathrm{nc}}}{\mathrm{dt}}\left(i\right)=\frac{u_{\mathrm{nc}}(i+1)-u_{\mathrm{nc}}(i-1)}{2h}.$ C ' _m, C _mRepresent between the double loop line respectively, alternate equivalent capacity, C _LBe double loop line mould equivalent capacity.

Three, finish the differential current protection at last:

A. select certain numerical filtering algorithm for use, the current i after each is compensated mutually ' _Ma(i), i ' _Mb(i), i ' _Mc(i) ... i ' _Ma(i+N), i ' _Mb(i+N), i ' _Mc(i+N) ... and i ' _Na(i), i ' _Nb(i), i ' _Nc(i) ... i ' _Na(i+N), i ' _Nb(i+N), i ' _Nc(i+N) ... calculate respectively and extract phasor

B. utilize formula (3), (4), the differential protection criterion is calculated in phase-splitting, judges $K_{\mathrm{cd}}=\left|\frac{{\stackrel{\&CenterDot;}{I}}_{\mathrm{cd}}}{{\stackrel{\&CenterDot;}{I}}_{\mathrm{zd}}}\right|=\left|\frac{{\stackrel{\&CenterDot;}{I}}_m^{\&prime;}+{\stackrel{\&CenterDot;}{I}}_n^{\&prime;}}{{\stackrel{\&CenterDot;}{I}}_m^{\&prime;}-{\stackrel{\&CenterDot;}{I}}_n^{\&prime;}}\right|>K$ And $I_{\mathrm{cd}}=|{\stackrel{\&CenterDot;}{I}}_m^{\&prime;}+{\stackrel{\&CenterDot;}{I}}_n^{\&prime;}|>I_0$ After, the phase-splitting action.

750kV double-circuit line on same pole to the Qian County carries out l-G simulation test through the Pingliang at East Lanzhou, uses above-mentioned example, can find: adopt traditional compensation method, the circuit differential current during external area error is about 250A; And employing the inventive method, the circuit differential current during external area error is about 50A, and protective value significantly improves.

Because being based on the Electrostatic Coupling model of double-circuit line on same pole, method disclosed by the invention carries out the compensation of capacitance current, single line down disconnects and the wait reclosing and actual capabilities occur, double loop enters non-full-operating state, and compensation method of the present invention this moment just has certain error.Consider the critical role of double loop in system, must guarantee the reliability of line differential protection, this is appropriate to the occasion temporarily to withdraw from this method, and still adopts the phasor or the time domain compensation method of single loop line.

Claims (1)

1, a kind of method for compensating time-domain capacitive current for double-circuit line on same pole, this method comprises following step:

(1) set up equivalent-circuit model: this model adopts static and the electromagnetic coupling effect between the alternate and line of П type circuit equivalent double loop;

(2) determine the offset current of two side loops according to equivalent-circuit model:

Electric current after M side I loop line C compensates mutually is:

$i_{\mathrm{mC}}^{\&prime;}=i_{\mathrm{mC}}-\frac{C_s}{2}\frac{{\mathrm{du}}_{\mathrm{mC}}}{\mathrm{dt}}-(\frac{C_m^{\&prime;}}{2}+\frac{C_m}{2})\frac{d(u_{\mathrm{mC}}-u_{\mathrm{mA}})}{\mathrm{dt}}-(\frac{C_m^{\&prime;}}{2}+\frac{C_m}{2})\frac{d(u_{\mathrm{mC}}-u_{\mathrm{mB}})}{\mathrm{dt}}$

$=i_{\mathrm{mC}}-\frac{C_s+3(C_m^{\&prime;}+C_m)}{2}\frac{{\mathrm{du}}_{\mathrm{mC}}}{\mathrm{dt}}+\frac{C_m^{\&prime;}+C_m}{2}\frac{{3\mathrm{du}}_0}{\mathrm{dt}}$

$=i_{\mathrm{mC}}-\frac{C_L}{2}\frac{{\mathrm{du}}_{\mathrm{mC}}}{\mathrm{dt}}+\frac{C_m^{\&prime;}+C_m}{2}\frac{{3\mathrm{du}}_{m0}}{\mathrm{dt}}---\left(1\right)$

Electric current after N side I loop line C compensates mutually is:

$i_{\mathrm{nC}}^{\&prime;}=i_{\mathrm{nC}}-\frac{C_L}{2}\frac{{\mathrm{du}}_{\mathrm{nC}}}{\mathrm{dt}}+\frac{C_m^{\&prime;}+C_m}{2}\frac{{3\mathrm{du}}_{n0}}{\mathrm{dt}}---\left(2\right)$

In formula (1) and (2), C ' _m, C _mAnd C _sRepresent between line respectively, alternate and equivalent capacity over the ground, Z _sBe the equivalent self-impedance of this phase,

The equivalent electromotive force of representing electromagnetic coupled between alternate and line; C _L=C _s+ 3 (C ' _m+ C _m) be double loop line mould electric capacity, 3u _M0=u _MA+ u _MB+ u _MC, 3u _N0=u _NA+ u _NB+ u _NC, u _MA, u _MB, u _MCAnd u _NA, u _NB, u _NCBe respectively the three-phase voltage at circuit two ends.

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