CN2687917Y

CN2687917Y - Split-phase brake device for preventing transformer differential protection from being malfunction using failure component

Info

Publication number: CN2687917Y
Application number: CN 200420020113
Authority: CN
Inventors: 徐习东
Original assignee: Zhejiang University ZJU
Current assignee: Zhejiang University ZJU
Priority date: 2004-02-13
Filing date: 2004-02-13
Publication date: 2005-03-23
Anticipated expiration: 2014-02-13

Abstract

The utility model relates to a phase-splitting braking device for preventing transformer differential protection from being false action using failure component. The device comprises a ratio braking element through using the suddenly-changed quantity of three phase difference motion current in a transformer differential protection device and the suddenly-changed quantity of zero sequence current. When the ratio value of the suddenly-changed quantity of the three phase difference motion current and the suddenly-changed quantity of the zero sequence current is smaller than a setting value K, a comparator exports 0. The corresponding phase difference motion current is judged as error current induced by an outer area fault, and the corresponding phase braking signal is exported. The corresponding phase difference motion protecting is carried on braking, preventing the false action of the transformer difference motion protecton device. Otherwise, the comparator exports 1 and permits the corresponding 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 protection device which the outer region earthing fault of the Y < 0 > side induces when the error of three-phase currenttransformers 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

Utilize fault component to prevent the phase-splitting brake apparatus of transformer differential protection malfunction

Technical field

The utility model relates to a kind of protection equipment for transformer, particularly a kind of phase-splitting brake apparatus that utilizes fault component to prevent the transformer differential protection malfunction

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 Y ₀The power transformer of/Δ wiring is for preventing Y ₀Lateral areas external ground fault zero-sequence current causes differential protection malfunction, extensively adopts Y at present ₀The side three-phase current carries out the method for conversion, eliminates the influence of zero-sequence current.But work as Y ₀Side threephase current transformer error is inconsistent, and transformer is only at the Y that external area error takes place ₀When side has power supply, can not eliminate Y by conventional method ₀The influence of the zero-sequence current that lateral areas external ground fault causes; bigger differential unsymmetrical current will be had; ratio brake element, the braking member that shoves can not reliably be braked this; especially very little even be under zero the situation at transformer opposite side load current; 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 phase-splitting brake apparatus that utilizes fault component to prevent the transformer differential protection malfunction; by with the sudden change amount of the three-phase differential current in the transformer differential protection respectively with the sudden change amount component ratio braking member of zero-sequence current; when the sudden change amount rate value of the sudden change amount of differential current and zero-sequence current 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.The utility model has the advantages that, in the time of can avoiding the threephase current transformer error inconsistent fully, Y ₀The transformer differential protection malfunction that lateral areas external ground fault causes, and the correct operation of differential protection under the zone of influence internal fault situation not.

A kind of phase-splitting brake apparatus that utilizes fault component to prevent the transformer differential protection malfunction; this device circuit constitutes as shown in Figure 1; it is characterized in that: this device is made of memory 11～14, subtracter 21～24, filter 31～34, multiplier 4, comparator 51～53, 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 is connected with the output of memory 11～13 respectively, its output connects the input of filter 31～33 respectively, the output of filter 31～33 connects the positive input terminal of comparator 51～53 respectively, and the positive input terminal of the input of memory 14 and subtracter 24 is input transformer Y respectively ₀Side zero-sequence current instantaneous value signal 3i ₀The negative input end of subtracter 24 connects the output of memory 14, the input of filter 34 is connected with the output of subtracter 24, an input of its output termination multiplier 4, another input input setting value K of multiplier 4, its output connects the negative input end of comparator 51～53 respectively, and comparator 51～53 is exported the brake signal of A, B, C phase respectively.Arrive under the same side, the same no-load voltage ratio situation in differential current and the equal reduction of zero-sequence current, setting value K is 0＜K＜1/3.When comparator positive input terminal signal 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, and corresponding phase differential protection is braked, and prevents the transformer differential protection malfunction; Otherwise comparator output 1 allows corresponding phase differential protection action.

With prior art relatively, the utility model has the advantages that proposed first in traditional transformer differential protection, to set up a kind of by with the differential current sudden change amount in the transformer differential protection respectively with zero-sequence current sudden change amount component ratio braking member, 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, Y ₀The transformer differential protection malfunction that lateral areas external ground fault 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 phase-splitting brake apparatus of transformer differential protection malfunction.

Embodiment

Embodiment 1

A kind of phase-splitting brake apparatus that utilizes fault component to prevent the transformer differential protection malfunction, this device circuit constitutes as shown in Figure 1, arrives under the same side, the same no-load voltage ratio situation in differential current and the equal reduction of zero-sequence current, and setting value K gets 0.2.When comparator 51～53 positive input terminal signals 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.The advantage of this device is, in the time of can avoiding the threephase current transformer error inconsistent fully, and Y ₀The transformer differential protection malfunction that lateral areas external ground fault causes, and the correct operation of differential protection under the zone of influence internal fault situation not.

Claims

1. phase-splitting brake apparatus that utilizes fault component to prevent the transformer differential protection malfunction; it is characterized in that: this device is made of memory (11～14), subtracter (21～24), filter (31～34), multiplier (4), comparator (51～53), 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) is connected with the output of memory (11～13) respectively, its output connects the input of filter (31～33) respectively, the output of filter (31～33) connects the positive input terminal of comparator (51～53) respectively, and the positive input terminal of the input of memory (14) and subtracter (24) is input transformer Y respectively _oSide zero-sequence current instantaneous value signal (3i _o), the negative input end of subtracter (24) connects the output of memory (14), the input of filter (34) is connected with the output of subtracter (24), an input of its output termination multiplier (4), another input input setting value (K) of multiplier (4), its output connects the negative input end of comparator (51～53) respectively, and comparator (51～53) is exported the brake signal of (A, B, C) phase respectively.

2. device 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 the equal reduction of zero-sequence current.

3 devices according to claim 1 is characterized in that: the characteristic of filter (31～34) should be consistent.