CN2689555Y

CN2689555Y - Split-phase braker for preventing multi-branch transformer differential protector from malfunction

Info

Publication number: CN2689555Y
Application number: CN 200420020117
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: 2005-03-30
Anticipated expiration: 2014-02-13

Abstract

The utility model relates to a phase splitting braking device for preventing a multi-branch transformer differential protection device from false action. The device comprises a ratio braking element through three-phase differential current acquired from a transformer differential protection device and the maximum value of the zero sequence current of every neutral point grounding side (or branch) of the transformer. The outer area grounding fault is judged by using the size of the ratio value. When the ratio value is smaller than the set value K, a comparator outputs 0. The corresponding phase differential current is judged as error current caused by an outer area fault, and the corresponding phase braking signal is output. The corresponding phase ratio differential protection device is braked, so as to prevent the false action of the transformer differential protection device. Otherwise, the comparator outputs 1 and permits the corresponding phase differential device to carry out action. The advantages of the project are that the utility model can completely avoid the false action of the transformer differential protection device caused by the outer region grounding fault of the neutral point grounding side, and the utility model does not influence the correct action of the differential protection device under the condition of the inner area fault.

Description

Prevent the phase-splitting brake apparatus of multiple-limb 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 prevents 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; this rate braking member; 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 prevents the malfunction of multiple-limb transformer differential protection, by the maximum component ratio braking member in the zero-sequence current of the three-phase differential current that from transformer differential protection, obtains and each neutral ground side (or branch), 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 ratio differential protection is braked, prevented the transformer differential protection malfunction; The utility model has the advantages that in the time of to avoid 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 phase-splitting brake apparatus that prevents the malfunction of multiple-limb transformer differential protection; this device circuit structure as shown in Figure 1; it is characterized in that: this device by filter 01,02 ... 0n, filter 11～13, maximizing circuit 2, multiplier 3, comparator 41～43 constitute, its median filter 01,02 ... the input of 0n is the zero-sequence current instantaneous value signal 3i of each neutral ground side (or branch) of input transformer respectively ₁₀, 3i ₂₀... 3i _N0Its output is connected with the input of maximizing circuit 2 respectively; the output of an input termination maximizing circuit 2 of multiplier 3; its another input input setting value K; the negative input end of comparator 41～43 connects the output of multiplier 3, and the input of filter 11～13 is imported the three-phase differential current instantaneous value signal i that obtains respectively from transformer differential protection _Da, i _Db, i _Dc, its output is connected with the positive input terminal of comparator 41～43 respectively, and comparator 41～43 is exported A phase, B phase, C phase brake signal respectively.Positive input terminal signal in comparator 41～43 is 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 ratio 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, n is a transformer neutral point ground connection side number (or branches).

With prior art relatively; the utility model has the advantages that by the maximum component ratio braking member in the zero-sequence current of the three-phase differential current that from transformer differential protection, obtains and each neutral ground side (or branch); when rate value during less than setting value K; declaring corresponding phase differential current is the error current that external area error causes, the corresponding phase ratio differential protection outlet of locking.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 not under the zone of influence internal fault situation, the correct operation of differential protection.

Description of drawings

Fig. 1 is the circuit block diagram that prevents the phase-splitting brake apparatus of multiple-limb transformer differential protection malfunction.

Embodiment

Embodiment 1

A kind of phase-splitting brake apparatus that prevents the malfunction of multiple-limb transformer differential protection, this device circuit constitutes as shown in Figure 1, and transformer neutral point ground connection side is counted n=3.When the positive input terminal signal in the comparator 41～43 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 ratio 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, K is 0.1.The advantage of this device is, the transformer differential protection malfunction that can avoid external ground fault in neutral ground lateral areas to cause fully, and not under the zone of influence internal fault situation, the correct operation of differential protection.

Claims

1. phase-splitting brake apparatus that prevents the malfunction of multiple-limb transformer differential protection; it is characterized in that: this device by filter (01,02 ... 0n), filter (11～13), maximizing circuit (2), multiplier (3), comparator (41～43) constitute, its median filter (01,02 ... input 0n) is the zero-sequence current instantaneous value signal (3i of each neutral ground side (or branch) of input transformer respectively ₁₀, 3i ₂₀3i _N0); its output is connected with the input of maximizing circuit (2) respectively; an input of the output termination multiplier (3) of maximizing circuit (2); another input input setting value (K) of multiplier (3); the negative input end of its output termination comparator (41～43), the input of filter (11～13) is imported the three-phase differential current instantaneous value signal (i that obtains respectively from transformer differential protection _Da, i _Db, i _Dc), its output is connected with the positive input terminal of comparator (41～43) respectively, and comparator (41～43) is exported (A) phase, (B) phase, (C) phase brake signal respectively, (n) is 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.