CN2711967Y - Negative sequence fault component difference stream comprehensive brake for preventing transformer protection from error action - Google Patents

Abstract

The utility model relates to a negative sequence fault component difference stream comprehensive brake for preventing transformer protection from error action. The device comprises a ratio braking element through the negative sequence suddenly-changed quantity of three phase difference motion current base wave in a transformer differential protection device and the weighting summation value of zero sequence current suddenly-changed quantity for each neutral point earthing side (or branch) of the transformer. When the signal of the positive input terminal of a comparator 8 is smaller than the signal of the negative input terminal, the comparator 9 exports 0. The situation is judged as an outer region earthing fault, and a three phase difference motion protecting outlet is closed. Otherwise, the comparator 9 exports 1 and permits the three phase difference motion protection device to do action. The advantages of the project are : the utility model can completely avoid the false action of the transformer difference motion protecting device which the outer region earthing fault of the neutral point earthing side induces when the error of the three-phase current transformers is inconsistent. The utility model doesn't influence the correct action of the difference motion protection device under the situation of the inner area fault.

Description

Specification prevents the negative phase-sequence fault component difference stream synthetical restraint device of malfunction for tranformer protection

Technical field

The utility model relates to a kind of protection equipment for transformer, particularly a kind of negative phase-sequence fault component difference stream synthetical restraint device that prevents malfunction for tranformer 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 utility model provides a kind of negative phase-sequence fault component difference stream synthetical restraint device that prevents malfunction for tranformer 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.The utility model has the advantages that, 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.

A kind of negative phase-sequence fault component difference stream synthetical restraint device that prevents malfunction for tranformer 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; the utility model has the advantages that and 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 is the circuit block diagram that prevents the negative phase-sequence fault component difference stream synthetical restraint device of malfunction for tranformer protection.

Embodiment

Embodiment 1

A kind of negative phase-sequence fault component difference stream synthetical restraint device that prevents malfunction for tranformer 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 fault component difference that prevents malfunction for tranformer protection flows 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 a 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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