CN1558510A - Negative sequence synthesized integrated brake device for preventing multiple-branch voltage transformer differential protection unwanted operation by utilizing fault components - Google Patents

Abstract

The invention discloses a negative sequence synthesized integrated brake device for preventing multiple-branch voltage transformer differential protection unwanted operation by utilizing fault components, wherein the three-phase difference currents in the transformer differential protection constitute ratio braking element with the maximum value of zero-sequence current on each of the neutral point earthing end (or branches), when the positive input end signal is less than the negative input end signal on the comparators, the comparator outputs 0, the lateral area outer ground fault is determined, the three-phase differential protection exit is locked, otherwise the comparator 9 outputs 1, and the corresponding differential protection actuations are allowed. The advantage of the invention is, the transformer differential protection accidental operation resulted from ground fault outside the lateral area when the errors of the three-phase current transformer are in inconformity without influencing the correct actuation of the differential protection under the circumstance of in-area faults.

Description

Utilize fault component to prevent the synthetic synthetical restraint device of negative phase-sequence of multiple-limb transformer differential protection malfunction

Technical field

The present invention relates to a kind of protection equipment for transformer, the synthetic synthetical restraint device of particularly a kind of negative phase-sequence of utilizing fault component to prevent the malfunction of multiple-limb transformer differential protection.

Background technology

Existing power transformer differential protection device by the ratio brake element, promptly by the ratio of differential current and through current, is discerned external area error and troubles inside the sample space; By shoving and the overexcitation braking member, promptly, discern magnetizing inrush current and overexcitation electric current simultaneously, reach the purpose of differentiating internal fault by analyzing the waveform or the harmonic content of differential current.To both sides being arranged or being the power transformer of neutral-point solid ground more than the both sides, when a ground connection side generating region external ground fault, may big earth fault zero-sequence current appear many sides.For preventing that this zero-sequence current from causing differential protection malfunction, extensively adopt the method that ground connection side three-phase current is carried out conversion at present, eliminate the influence of zero-sequence current.But it is inconsistent to work as ground connection side threephase current transformer error; and transformer is only when the neutral ground side that external area error takes place has power supply; can not eliminate the influence of the zero-sequence current that external ground fault in neutral ground lateral areas causes by conventional method; bigger differential unsymmetrical current will be had; the ratio brake element; the braking member that shoves can not reliably be braked this; especially very little even be under zero the situation at the transformer load electric current; the ratio brake element; the braking member that shoves can not be braked this; as long as error current surpasses threshold, transformer differential protection is with malfunction.

Summary of the invention

The purpose of this invention is to provide the synthetic synthetical restraint device of a kind of negative phase-sequence of utilizing fault component to prevent the malfunction of multiple-limb transformer differential protection; the weighted sum value component ratio braking member of the first-harmonic negative phase-sequence sudden change amount by the three-phase differential current in the transformer differential protection and the zero-sequence current sudden change amount of each neutral ground side (or branch) of transformer; when rate value during less than setting value K; be judged to district's external ground fault, the outlet of locking three-phase differential protection.Advantage of the present invention is, in the time of can avoiding the threephase current transformer error inconsistent fully, and the transformer differential protection malfunction that external ground fault in neutral ground lateral areas causes.

The synthetic synthetical restraint device of a kind of negative phase-sequence of utilizing fault component to prevent the malfunction of multiple-limb transformer differential protection, this device circuit constitutes as shown in Figure 1.It is characterized in that: this device by memory 11～13, subtracter 21～23, first-harmonic negative sequence filter 31, filter 32, memory 41,42 ... 4n, subtracter 51,52 ... 5n, filter 61,62 ... 6n, multiplier 71,72 ... 7n, adder 81, multiplier 82, comparator 9 constitute, wherein the three-phase differential current instantaneous value signal i of the positive input terminal of the input of memory 11～13 and subtracter 21～23 difference input transformer differential protection formation _Da, i _Db, i _DcThe negative input end of subtracter 21～23 connects the output of memory 11～13 respectively, its output is connected with three inputs of first-harmonic negative sequence filter 31 respectively, the output of the input termination first-harmonic negative sequence filter 31 of filter 32, the positive input terminal of its output termination comparator 9; Memory 41,42 ... the input of 4n and subtracter 51,52 ... the positive input terminal of 5n is the zero-sequence current instantaneous value signal 3i of each neutral ground side (or branch) of input transformer respectively ₁₀, 3i ₂₀... 3i _N0Subtracter 51,52 ... the negative input end of 5n connect respectively memory 41,42 ... the output of 4n, its output respectively with filter 61,62 ... the input of 6n is connected, multiplier 71,72 ... the input of 7n connect respectively filter 61,62 ... the output of 6n, its another input are imported respectively and are preestablished weights k ₁₀, k ₂₀... k _N0The input of adder 81 connect respectively multiplier 71,72 ... the output of 7n, an input of its output and multiplier 82 joins, another input input setting value K of multiplier 82, the negative input end of its output termination comparator 9, comparator 9 output three-phase brake signals.Arrive the same side, same no-load voltage ratio and weights 0＜(k in differential current and zero-sequence current reduction ₁₀, k ₂₀... k _N0Under the situation of)≤1, setting value K is 0＜K＜1, and n is a transformer neutral point ground connection side number (or branches).When the positive input terminal signal of comparator 9 less than the negative input end signal, comparator 9 outputs 0 are judged to district's external ground fault, the outlet of locking three-phase differential protection; Otherwise comparator 9 outputs 1 allow the action of three-phase differential protection.

With prior art relatively; advantage of the present invention is to have proposed first in traditional transformer differential protection; add a kind of by the three-phase differential current in the transformer differential protection first-harmonic negative phase-sequence sudden change amount and the weighted sum value component ratio braking member of the zero-sequence current sudden change amount of each neutral ground side (or branch) of transformer; when rate value during less than setting value K; be judged to district's external ground fault, the outlet of locking three-phase differential protection.Use this programme; in the time of can avoiding the threephase current transformer error inconsistent fully; the transformer differential protection malfunction that external ground fault in neutral ground lateral areas causes; also can prevent under other non-internal fault situations; the transformer differential protection misoperation that the differential unsymmetrical current that zero-sequence current causes causes, and the correct operation of differential protection under the zone of influence internal fault situation not.

Description of drawings

Fig. 1 utilizes fault component to prevent the circuit block diagram of the synthetic synthetical restraint device of negative phase-sequence of multiple-limb transformer differential protection malfunction.

Embodiment

Embodiment 1

The synthetic synthetical restraint device of a kind of negative phase-sequence of utilizing fault component to prevent the malfunction of multiple-limb transformer differential protection, its circuit constitutes as shown in Figure 1, and transformer neutral point ground connection side is counted n=3.When the signal of comparator 9 positive input terminals during less than the negative input end signal, comparator 9 outputs 0 are judged to district's external ground fault, the outlet of locking three-phase differential protection; Otherwise comparator 9 outputs 1 allow the action of three-phase differential protection.When differential current and zero-sequence current reduction to the same side, same no-load voltage ratio and weights k ₁₀=0.8, k ₂₀=0.6, k ₃₀Under=0.3 the situation, setting value K is 0.2.The advantage of this device is, in the time of can avoiding the threephase current transformer error inconsistent fully, and the transformer differential protection malfunction that external ground fault in neutral ground lateral areas causes, and the correct operation of differential protection under the zone of influence internal fault situation not.

Claims (2)

1. a negative phase-sequence of utilizing fault component to prevent the malfunction of multiple-limb transformer differential protection is synthesized the synthetical restraint device; it is characterized in that: this device is by memory (11～13); subtracter (21～23); first-harmonic negative sequence filter (31); filter (32); memory (41; 42; 4n); subtracter (51; 52; 5n); filter (61; 62; 6n); multiplier (71; 72; 7n); adder (81); multiplier (82); comparator (9) constitutes, wherein the three-phase differential current instantaneous value signal (i of the positive input terminal of the input of memory (11～13) and subtracter (21～23) difference input transformer differential protection formation _Da, i _Db, i _Dc), the negative input end of subtracter (21～23) connects the output of memory (11～13) respectively, its output is connected with three inputs of first-harmonic negative sequence filter (31) respectively, the output of the input termination first-harmonic negative sequence filter (31) of filter (32), the positive input terminal of its output termination comparator (9), memory (41,42 ... input 4n) and subtracter (51,52 ... positive input terminal 5n) is the zero-sequence current instantaneous value signal (3i of each neutral ground side (or branch) of input transformer respectively ₁₀, 3i ₂₀... 3i _N0), subtracter (51,52 ... negative input end 5n) connect respectively memory (41,42 ... output 4n), its output respectively with filter (61,62 ... input 6n) is connected, multiplier (71,72 ... input 7n) connect respectively filter (61,62 ... output 6n), its another input are imported respectively and are preestablished weights (k ₁₀, k ₂₀... k _N0), the input of adder (81) connect respectively multiplier (71,72 ... output 7n), an input of its output and multiplier (82) joins, another input input setting value (K) of multiplier (82), the negative input end of its output termination comparator (9), comparator (9) output three-phase brake signal (n) is transformer neutral point ground connection side number (or branches).

2. brake apparatus according to claim 1 is characterized in that: differential current and zero-sequence current reduction to the same side, same no-load voltage ratio and weights 0＜(k ₁₀, k ₂₀... k _N0Under the situation of)≤1, setting value (K) is 0＜K＜1.

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