CN2689552Y

CN2689552Y - Three-phase braker for preventing transformer differential protector from malfunction by fault component

Info

Publication number: CN2689552Y
Application number: CN 200420020114
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 three-phase braking device for preventing transformer differential protection device from false action. The device comprises a ratio braking element through the suddenly-changed quantity of three phase difference motion current in a transformer difference motion protection device and the suddenly-changed quantity of zero sequence current respectively. When the signal of the positive input terminals of comparators 51-53 is smaller than the signal of the negative input terminals, the comparators export 0. The corresponding phase difference motion current is judged as error current induced by an outer area fault, the signal is exported by way of an or gate 6. When the or gate 6 exports 0, a three phase difference motion protecting outlet is closed. Otherwise, the or gate 6 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 protection device which the outer region earthing fault of the Y < 0 > side induces when the error of 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

Utilize fault component to prevent the three-phase 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 three-phase 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 three-phase brake apparatus that utilizes fault component to prevent the transformer differential protection malfunction; by with the three-phase differential current sudden change amount in the transformer differential protection respectively with the sudden change amount component ratio braking member of zero-sequence current; when the rate value of the sudden change amount of the sudden change amount of three-phase 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; signal through or door output after, 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, 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 three-phase brake apparatus that utilizes fault component to prevent the transformer differential protection malfunction; its circuit constitutes as shown in Figure 1; it is characterized in that: this device is made of memory 11～1 4, subtracter 21～24, filter 31～34, multiplier 4, comparator 51～53 or door 6, wherein the three-phase differential current instantaneous value signal i of the positive input terminal of the input of memory 11～1 3 and subtracter 21～23 difference input transformer differential protection formation _Da, i _Db, i _DcThe output of memory 11～13 connects the negative input end of subtracter 21～23 respectively, the output of subtracter 21～23 connects the input of filter 31～33 respectively, the output of filter 31～33 connects the positive input terminal of comparator 51～53 respectively, the positive input terminal input transformer Y of the input of memory 14 and subtracter 24 _oSide zero-sequence current instantaneous value signal 3io, the negative input end of subtracter 24 is connected with the output of memory 14, the input of its output termination filter 34, an input of the output termination multiplier 4 of filter 34, another input input setting value K of multiplier 4, its output connects the negative input end of comparator 51～53 respectively, the output of comparator 51～53 respectively with or door three inputs of 6 be connected or the output of door 6 output three-phase brake signal.Arrive the same side in differential current and the equal reduction of zero-sequence current, under the same no-load voltage ratio situation, setting value K is 0＜K＜1/3.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; otherwise comparator output 1; signal through or door 6 outputs, or door 6 outputs 0 o'clock, locking three-phase differential protection outlet; or door 6 outputs 1, allow the action of three-phase differential protection.

With prior art relatively; the utility model has the advantages that proposed first in traditional transformer differential protection, to set up by with the differential current sudden change amount in the transformer differential protection respectively with the ratio brake element of zero-sequence current sudden change amount; when the rate value of the sudden change amount of the sudden change amount of three-phase 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; signal warp or door output, the outlet of locking three-phase differential protection.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 three-phase brake apparatus of transformer differential protection malfunction.

Embodiment

A kind of three-phase brake apparatus that utilizes fault component to prevent the transformer differential protection malfunction, this device circuit constitutes as shown in Figure 1, arrives the same side in differential current and the equal reduction of zero-sequence current, and under the same no-load voltage ratio situation, setting value K is 0.1.When comparator 51～53 positive input terminal signals less than the negative input end signal, comparator output 0, otherwise export 1, signal through or door 6 outputs.Or door 6 was exported locking three-phase differential protection general export at 0 o'clock; Or door 6 was exported the action of permission three-phase differential protection at 1 o'clock.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. three-phase 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) or door (6), wherein the three-phase differential current instantaneous value signal (i of the positive input terminal of the input of memory (11～1 3) 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) is connected with the output of memory (14), the input of its output termination filter (34), an input of the output termination multiplier (4) of filter (34), another input input setting value (K) of multiplier (4), its output connects the negative input end of comparator (51～53) respectively, the output of comparator (51～53) respectively with or three inputs of door (6) be connected or the output output three-phase brake signal of door (6).

2. device according to claim 1 is characterized in that: to the same side, under the 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 (11～14) should be consistent.