CN2689559Y - Positive sequential differential flow comprehensive braker for preventing multi-branch transformer differential protector from malfunction - Google Patents

Abstract

The utility model relates to a positive sequential differential flow comprehensive braking device for preventing multi-branch transformer differential protector from malfunction. The device comprises a ratio braking element through the positive sequential current of the base wave of three phase difference motion current acquired from a transformer difference motion protection device and the weighting summation value of the zero sequence current of each neutral point earthing side (or branch). When the ratio value is smaller than a setting value K, a comparator 6 exports 0. The situation is judged as an outer region earthing fault, and a general three phase difference motion protecting outlet is closed. Otherwise, the comparator 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 differential protection device which the outer region earthing fault of the neutral point earthing side induces when the error of the three-phase current transformers is inconsistent.

Description

Prevent the positive sequence difference stream synthetical restraint device 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 positive sequence difference stream synthetical restraint device 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; 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 utility model provides a kind of positive sequence difference stream synthetical restraint device that prevents the malfunction of multiple-limb transformer differential protection; the weighted sum value component ratio braking member of the fundamental positive sequence electric current by the three-phase differential current that from transformer differential protection, obtains and the zero-sequence current of each neutral ground side (or branch); when rate value during less than setting value K; be judged to district's external ground fault, 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, the transformer differential protection malfunction that external ground fault in neutral ground lateral areas causes.

A kind of positive sequence difference stream synthetical restraint device that prevents the malfunction of multiple-limb transformer differential protection; the circuit of this device constitutes as shown in Figure 1; it is characterized in that: this device by filter 01,02 ... 0n, fundamental positive sequence pass filter 1, filter 2, multiplier 31,32 ... 3n, adder 4, multiplier 5, comparator 6 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 _N0, its output connect respectively multiplier 31,32 ... the input of 3n, multiplier 31,32 ... another input of 3n is imported respectively and is preestablished weights k ₁₀, k ₂₀... k _N0Its output connects the input of adder 4 respectively; an input of multiplier (5) is connected with the output of adder (4); its another input input setting value K; the negative input end of comparator 6 connects the output of multiplier 5, and three inputs of fundamental positive sequence pass filter 1 are imported the three-phase differential current instantaneous value signal i that obtains respectively from transformer differential protection _Da, i _Db, i _Dc, its output termination filter 2 inputs, the positive input terminal of the output of filter 2 and comparator 6 joins, comparator 6 output three-phase brake signals.Arrive the same side, same no-load voltage ratio and weights 0＜(k in differential current and zero-sequence current reduction ₁₀, k ₂₀... k _N0Under the situation of)≤1, setting value K is 0＜K＜1, and n is a transformer neutral point ground connection side number (or branches).When the positive input terminal signal of comparator 6 less than the negative input end signal, comparator 6 outputs 0 are judged to district's external ground fault, the outlet of locking rate of three phase flow differential protection; Otherwise comparator 6 outputs 1 allow the action of three-phase differential protection.

With prior art relatively; the utility model has the advantages that and proposed first in traditional multiple-limb transformer differential protection; add a kind of fundamental positive sequence electric current and ratio brake element of constituting of the zero-sequence current weighted sum value of each neutral ground side (or branch) of transformer by the three-phase differential current that from transformer differential protection, obtains; when rate value during less than setting value K; be judged to district's external ground fault, locking rate of three phase flow differential protection general export.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 positive sequence difference stream synthetical restraint device of multiple-limb transformer differential protection malfunction.

Embodiment

Embodiment 1

A kind of positive sequence difference stream synthetical restraint device 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 of comparator 6 during less than the negative input end signal, comparator 6 outputs 0 are judged to district's external ground fault, locking rate of three phase flow differential protection general export; Otherwise comparator 6 outputs 1 allow the action of three-phase differential protection.Arrive the same side, same no-load voltage ratio and weights k in differential current and zero-sequence current reduction ₁₀=0.8, k ₂₀=0.6, k ₃₀Under=0.3 the situation, setting value K gets 0.8.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. a positive sequence difference that prevents the malfunction of multiple-limb transformer differential protection flows the synthetical restraint device; it is characterized in that: this device by filter (01,02 ... 0n), fundamental positive sequence pass filter (1), filter (2), multiplier (31,32 ... 3n), adder (4), multiplier (5), comparator (6) 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 ₂₀... 3i _N0), its output connect respectively multiplier (31,32 ... input 3n), multiplier (31,32 ... another input 3n) is imported respectively and is preestablished weights (k ₁₀, k ₂₀... k _N0); its output connects the input of adder (4) respectively; an input of multiplier (5) is connected with the output of adder (4); its another input input setting value (K); the negative input end of comparator (6) connects the output of multiplier (5), and three inputs of fundamental positive sequence pass filter (1) are imported the three-phase differential current instantaneous value signal (i that obtains respectively from transformer differential protection _Da, i _Db, i _Dc), the input of its output termination filter (2), the positive input terminal of the output of filter (2) and comparator (6) joins, and comparator (6) output three-phase brake signal (n) is transformer neutral point ground connection side number (or branches).

2. brake apparatus according to claim 1 is characterized in that: differential current and zero-sequence current reduction to the same side, same no-load voltage ratio and weights 0＜(k ₁₀, k ₂₀... k _N0Under the situation of)≤1, setting value (K) is 0＜K＜1.

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