CN2687915Y - Split-phase brake device for preventing transformer differential protection from being malfunction - Google Patents

Abstract

The utility model relates to a braking device for preventing transformer differential protection from being false action. The device comprises a ratio braking element by using three phase difference motion current in a transformer differential protection device and the zero sequence current of a Y < 0 > side respectively. According to the size of ratio value, the outer area earthing fault of the Y < 0 > side is distinguished. When the ratio value is smaller than the 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 ratio difference motion protection device is carried on braking, preventing the false action of the transformer differential protection 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 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

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 prevents 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 prevents the transformer differential protection malfunction, by with the three-phase differential current in the transformer differential protection respectively with Y ₀The zero-sequence current component ratio braking member of side; when differential current and zero-sequence current 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 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 prevents the transformer differential protection malfunction; this device circuit constitutes as shown in Figure 1; it is characterized in that: this device is made of filter 11～14, multiplier 2, comparator 31～33, and the input of its median filter 11～13 is A, B, the C three-phase differential current instantaneous value signal i of the formation of input transformer differential protection respectively _Da, i _Db, i _Dc, the input input transformer Y of filter 14 ₀Side zero-sequence current instantaneous value signal 3i ₀An input of its output termination multiplier 2, another input input setting value K of multiplier 2, the negative input end of comparator 31～33 is connected with the output of multiplier 2, its positive input terminal connects the output of filter 11～13 respectively, and comparator 31～33 is exported the brake signal of A, B, C phase respectively.Positive input terminal signal in comparator 31～33 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 situation of the same side, same no-load voltage ratio in differential current and the equal reduction of zero-sequence current, setting value K is 0＜K＜1/3; Filter 11～14 characteristics require consistent.

With prior art relatively; the utility model has the advantages that and proposed in traditional transformer differential protection, to set up the ratio brake element that constitutes with zero-sequence current respectively with the three-phase differential current in the transformer differential protection first; when differential current and zero-sequence current rate value during less than setting value K; export corresponding phase brake signal; corresponding phase ratio 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 is the circuit block diagram that prevents the phase-splitting brake apparatus of transformer differential protection malfunction.

Embodiment

Embodiment 1:

A kind of phase-splitting brake apparatus that prevents the transformer differential protection malfunction, its circuit constitutes as shown in Figure 1, when comparator 31～33 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, export corresponding phase brake signal, the corresponding phase ratio differential protection outlet of locking; Otherwise comparator output 1 allows corresponding phase differential protection action.Arrive under the situation of the same side, same no-load voltage ratio in differential current and the equal reduction of zero-sequence current, setting value K is 0.1.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 (3)

1. phase-splitting brake apparatus that prevents the transformer differential protection malfunction; it is characterized in that: this device is made of filter (11～14), multiplier (2), comparator (31～33), and the input of its median filter (11～13) is (A, B, C) three-phase differential current instantaneous value signal (i of input transformer differential protection formation respectively _Da, i _Db, i _Dc), the input input transformer Y of filter (14) _oSide zero-sequence current instantaneous value signal (3i _o), an input of its output termination multiplier (2), another input input setting value (K) of multiplier (2), the negative input end of comparator (31～33) is connected with the output of multiplier (2), its positive input terminal connects the output of filter (11～13) respectively, and comparator (31～33) is exported the brake signal of (A, B, C) phase respectively.

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

3 devices according to claim 1 is characterized in that: the characteristic of filter (11～14) should be consistent.