CN2711960Y - Fault component phase spliting zero sequence brake for preventing transformer protection from error action - Google Patents

Abstract

The utility model relates to a fault component phase splitting zero sequence brake for preventing the transformer protection from error action. The device comprises a ratio braking element which is composed of the suddenly-changed quantity of the three-phase differential current in a transformer differential protection device together with the maximum value of the suddenly-changed quantity of the zero sequence current of each neutral point earthing side (or branch) of the transformer respectively. When the ratio value is smaller than the setting value K, a comparator outputs 0. The corresponding phase differential current is judged as an error current induced by an outer area fault and the corresponding phase braking signal is output. The corresponding phase differential protection is braked, preventing the false action of the transformer differential protection device. Otherwise, the comparator outputs 1 and permits the corresponding phase differential protection device to act. The advantages of the project are that the utility model can completely avoid the false action of the transformer differential protection device induced by the outer area earthing fault of the neutral point earthing side. This fault component phase splitting zero sequence brake for preventing the transformer protection from error action doesn't influence the correct action of the differential protection device under the situation of the inner area fault.

Description

Prevent the fault component split-phase zero-sequence braking device of malfunction for tranformer protection

Technical field

The present invention relates to a kind of protection equipment for transformer, particularly a kind of fault component split-phase zero-sequence braking 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; Simultaneously by shoving and the overexcitation braking member, promptly, discern magnetizing inrush current and overexcitation electric current by analyzing the waveform or the harmonic content of differential current,, reach the purpose of differentiation internal fault.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 a kind of fault component split-phase zero-sequence braking device that prevents malfunction for tranformer protection, by the three-phase differential current sudden change amount in the transformer differential protection respectively with the maximum 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, declaring corresponding phase differential current is the error current that external area error causes, export corresponding phase brake signal, corresponding phase differential protection is braked, prevented the transformer differential protection malfunction; 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.

A kind of fault component split-phase zero-sequence braking 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, filter 31～33, memory 41,42 ... 4n, subtracter 51,52 ... 5n, filter 61,62 ... 6n, maximizing circuit 71, multiplier 72, comparator 81～83 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 _Dc, the negative input end of subtracter 21～23 connects the output of memory 11～13 respectively, and its output connects the input of filter 31～33 respectively, and the output of filter 31～33 connects the positive input terminal of comparator 81～83 respectively; 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, the input of maximizing circuit 71 connect respectively filter 61,62 ... the output of 6n, an input of its output termination multiplier 72, another input input setting value K of multiplier 72, its output connects the negative input end of comparator 81～83 respectively, and comparator 81～83 is exported the brake signal of A, B, C phase respectively.When the signal of comparator 81～83 positive input terminals less than the negative input end signal, comparator output 0, declaring corresponding phase differential current is the error current that external area error causes, exports corresponding phase brake signal, corresponding phase differential protection is braked, prevented the transformer differential protection malfunction; Otherwise comparator output 1 allows corresponding phase differential protection action.Arrive under the same side, the same no-load voltage ratio situation in differential current and zero-sequence current reduction, setting value K is 0＜K＜1/3, and n is a transformer neutral point ground connection side number (or branches).

With prior art relatively; advantage of the present invention is to have proposed to set up in traditional transformer differential protection a kind of ratio brake element that constitutes with the maximum of the zero-sequence current sudden change amount of each neutral ground side (or branch) of transformer respectively by the three-phase differential current sudden change amount in the transformer differential protection first; when rate value during less than setting value K; declaring corresponding phase differential current is the error current that external area error causes; export corresponding phase brake signal; corresponding phase differential protection is braked, prevented the transformer differential protection malfunction.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 fault component split-phase zero-sequence braking device of malfunction for tranformer protection.

Embodiment

Embodiment 1

A kind of fault component split-phase zero-sequence braking 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 the positive input terminal in the comparator 81～83 during less than the negative input end signal, comparator output 0, declaring corresponding phase differential current is the error current that external area error causes, exports corresponding phase brake signal, corresponding phase differential protection is braked, prevented the transformer differential protection malfunction; Otherwise comparator output 1 allows corresponding phase differential protection action.When differential current and zero-sequence current reduction under the same side, same no-load voltage ratio situation, setting value K gets 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. fault component split-phase zero-sequence braking device that prevents malfunction for tranformer protection; it is characterized in that: this device is by memory (11～13); subtracter (21～23); filter (31～33); memory (41; 42; 4n); subtracter (51; 52; 5n); filter (61; 62; 6n); maximizing circuit (71); multiplier (72); comparator (81～83) 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, and its output is connected with the input of filter (31～33) respectively, and the output of filter (31～33) connects the positive input terminal of comparator (81～83) respectively; 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) connects memory (41 respectively, 42, output 4n), its output connects filter (61 respectively, 62, input 6n), the input of maximizing circuit (71) respectively with filter (61,62, output 6n) is connected, an input of its output termination multiplier (72), another input input setting value (K) of multiplier (72), its output connects the negative input end of comparator (81～83) respectively, comparator (81～83) is exported (A respectively, B, C) brake signal of phase, n are transformer neutral point ground connection side number (or branches).

2. brake apparatus according to claim 1 is characterized in that: under the same side, same no-load voltage ratio situation, setting value (K) is 0＜K＜1/3 in differential current and zero-sequence current reduction.