CN100394656C - Maximum interphase and zero-sequence fault component braking method for preventing malfunction for transformer protection - Google Patents

Abstract

The present invention discloses a maximum inter-phase and zero-sequence fault component braking method for preventing the malfunction of protection for transformers; a ratio braking element is composed of the maximum value of an inter-phase electric current fault component after Y/delta conversion from a three-phase electric current fault component at the Y0 side of the transformer and a zero-sequence electric current fault component at the side; when a ratio value is smaller than a definite value, a three-phase braking signal is output to stop differential protection for transformer radios. The application of the proposal only collects the three-phase electric current of the Y0 side with a power supply and uses the ratio braking element composed of the maximum value of the inter-phase electric current fault component at the single side and the zero-sequence electric current fault component at the side, which can thoroughly avoid the malfunction of differential protection for transformers caused by an external grounding fault at the Y0 side when the errors of a three-phase electric current transformer are not consistent and can prevent the malfunction of differential protection for transformers caused by the zero sequence electric current resulting in differential unbalance electric currents under the condition of other non-internal faults.

Description

Prevent between the maximal phase of malfunction for tranformer protection and zero-sequence fault component braking method

Technical field

The present invention relates to a kind of relay protection method of power system, between particularly a kind of maximal phase that prevents malfunction for tranformer protection and zero-sequence fault component braking method.

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; Simultaneously,, promptly, discern magnetizing inrush current and overexcitation electric current, reach the purpose of differentiating internal fault by analyzing the waveform or the harmonic content of differential current by shoving and the overexcitation braking member.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; the ratio brake element, shove and the overexcitation braking member can not reliably be braked this; especially very little even be under zero the situation at the transformer load electric 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.In number of patent application is 200410016307.7 " utilizing fault component to prevent that the branch of transformer differential protection malfunction from differing the stream method ", the sudden change amount by differential current and the sudden change amount of zero-sequence current recently differentiate Y ₀Though the method for lateral areas external ground fault can overcome above-mentioned defective, differential current is gathered complicated.

Summary of the invention

The technical problem to be solved in the present invention is the Y that exists in the existing transformer differential protection technology ₀Side three-phase current transform method can not be eliminated the influence of zero-sequence current fully, provides between a kind of maximal phase that prevents malfunction for tranformer protection and zero-sequence fault component braking method, uses transformer Y ₀The three-phase current fault component of side carries out maximum and this side zero-sequence current fault component component ratio braking member of gained three-phase current fault component after the conversion of Y/ Δ; when rate value during less than setting value; output three-phase brake signal; the transformer ratio differential protection is braked, prevented the transformer differential protection malfunction.Advantage of the present invention is, relies on one-sided three-phase current and this side zero-sequence current, uses transformer Y ₀The maximum of the three-phase current fault component of side and this side zero-sequence current fault component component ratio are braked when avoiding the threephase current transformer error inconsistent fully Y ₀The transformer differential protection malfunction that lateral areas external ground fault causes.

Between a kind of maximal phase that prevents malfunction for tranformer protection and zero-sequence fault component braking method, it is characterized in that: use transformer Y ₀The three-phase current fault component of side carries out maximum and this side zero-sequence current fault component component ratio braking criterion of gained three-phase current fault component after the conversion of Y/ Δ, as transformer Y ₀During less than setting value, brake the transformer ratio differential protection by output three-phase brake signal divided by the rate value of this side zero-sequence current fault component for the maximum that the three-phase current fault component of side carries out gained three-phase current fault component after the conversion of Y/ Δ; Foundation with zero-sequence fault component braking between maximal phase is:

${\left(\right|\mathrm{\Δ}{\stackrel{\·}{I}}_a-\mathrm{\Δ}{\stackrel{\·}{I}}_b|,|\mathrm{\Δ}{\stackrel{\·}{I}}_b-\mathrm{\Δ}{\stackrel{\·}{I}}_c|,|\mathrm{\Δ}{\stackrel{\·}{I}}_c-\mathrm{\Δ}{\stackrel{\·}{I}}_a\left|\right)}_{\max }/\left|\mathrm{\Δ}3{\stackrel{\·}{I}}_0\right|$

$<K$

Δ I in the formula ₀,

Be respectively transformer Y ₀The three-phase current fault component vector of side, ${\left(\right|\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{I}}_a-\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{I}}_b|,|\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{I}}_b-\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{I}}_c|,|\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{I}}_c-\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{I}}_a\left|\right)}_{\max }$ Be transformer Y ₀The three-phase current fault component vector of side carries out the maximum of gained three-phase current fault component after the conversion of Y/ Δ,

For this side zero-sequence current fault component vector (promptly $\mathrm{\&Delta;}3{\stackrel{\&CenterDot;}{I}}_0=\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{I}}_a+$ $\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{I}}_b+\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{I}}_c),$ K is a setting value, and its value is 0＜K＜1/3.

With prior art relatively, the invention has the beneficial effects as follows to have proposed first in traditional transformer differential protection, set up and use transformer Y ₀The three-phase current fault component of side carries out maximum and this side zero-sequence current fault component component ratio braking member of gained three-phase current fault component after the conversion of Y/ Δ; when rate value during less than setting value; output three-phase brake signal; the transformer ratio differential protection is braked, prevented the transformer differential protection malfunction.Use this programme, only need to gather the Y that power supply is arranged ₀Side three-phase current and this side zero-sequence current are used transformer Y ₀The maximum of the three-phase current fault component of side and this side zero-sequence current fault component component ratio braking member, in the time of just 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.

Description of drawings

Fig. 1 is for realizing between a kind of maximal phase that prevents malfunction for tranformer protection of the present invention circuit block diagram with the zero-sequence fault component braking element.

Embodiment

Embodiment 1:

Between a kind of maximal phase that prevents malfunction for tranformer protection and zero-sequence fault component braking method, this method can prevent between the maximal phase of malfunction for tranformer protection to be achieved with the circuit block diagram of zero-sequence fault component braking element by Fig. 1 a kind of.This element is made of memory 1～4, subtracter 01～04,11～13, filter 21～24, maximizing circuit 31, multiplier 32 and comparator 33.Wherein the positive input terminal of the input of memory 1～3 and subtracter 01～03 is distinguished input transformer Y ₀The three-phase current instantaneous value signal i of side _a, i _b, i _c, the output of memory 1～3 connects the negative input end of subtracter 01～03 respectively, and the output of subtracter 01～03 connects the positive input terminal of subtracter 11～13 respectively; The negative input end of subtracter 11,12,13 conversion respectively is connected with the positive input terminal of subtracter 12,13,11, and its output connects the input of filter 21～23 respectively; The output of filter 21～23 is connected with three inputs of maximizing circuit 21 respectively; The positive input terminal of the input of memory 4 and subtracter 04 is input transformer Y respectively ₀Side zero-sequence current instantaneous value signal 3i _o, the negative input end of the output termination subtracter 04 of memory 4, the output of subtracter 04 is connected with the input of filter 24; The output of an input termination filter 24 of multiplier 32, another input input setting value K=0.3, its output connects the negative input end of comparator 33 respectively; The positive input terminal of comparator 33 is connected with the output of maximizing circuit 31, its output output three-phase brake signal.When the positive input terminal signal of comparator less than the negative input end signal, comparator output three-phase brake signal is braked the transformer ratio differential protection, prevents the transformer differential protection malfunction.Use this programme, only need to gather the transformer Y that power supply is arranged ₀The three-phase current of side is used Y ₀The three-phase current fault component of side carries out maximum and this side zero-sequence current fault component component ratio braking member of gained three-phase current fault component after the conversion of Y/ Δ, in the time of just can avoiding the threephase current transformer error inconsistent fully, and 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.

Claims (2)

1. between a maximal phase that prevents malfunction for tranformer protection and zero-sequence fault component braking method, it is characterized in that: use transformer Y ₀The three-phase current fault component of side carries out maximum and this side zero-sequence current fault component component ratio braking criterion of gained three-phase current fault component after the conversion of Y/ Δ, as transformer Y ₀During less than setting value, brake the transformer ratio differential protection by output three-phase brake signal divided by the rate value of this side zero-sequence current fault component for the maximum that the three-phase current fault component of side carries out gained three-phase current fault component after the conversion of Y/ Δ; Foundation with zero-sequence fault component braking between maximal phase is:

${\left(\right|{\mathrm{\&Delta;}\stackrel{\&CenterDot;}{I}}_a-{\mathrm{\&Delta;}\stackrel{\&CenterDot;}{I}}_b|,|{\mathrm{\&Delta;}\stackrel{\&CenterDot;}{I}}_b-{\mathrm{\&Delta;}\stackrel{\&CenterDot;}{I}}_c|,|{\mathrm{\&Delta;}\stackrel{\&CenterDot;}{I}}_c-{\mathrm{\&Delta;}\stackrel{\&CenterDot;}{I}}_a\left|\right)}_{\max }/\left|{\mathrm{\&Delta;}3\stackrel{\&CenterDot;}{I}}_0\right|$

$<K$

In the formula

Be respectively transformer Y ₀The three-phase current fault component vector of side, ${\left(\right|{\mathrm{\&Delta;}\stackrel{\&CenterDot;}{I}}_a-{\mathrm{\&Delta;}\stackrel{\&CenterDot;}{I}}_b|,|{\mathrm{\&Delta;}\stackrel{\&CenterDot;}{I}}_b-{\mathrm{\&Delta;}\stackrel{\&CenterDot;}{I}}_c|,|{\mathrm{\&Delta;}\stackrel{\&CenterDot;}{I}}_c-{\mathrm{\&Delta;}\stackrel{\&CenterDot;}{I}}_a\left|\right)}_{\max }$ Be transformer Y ₀The three-phase current fault component vector of side carries out the maximum of gained three-phase current fault component after the conversion of Y/ Δ,

Be this side zero-sequence current fault component vector, promptly ${\mathrm{\&Delta;}3\stackrel{\&CenterDot;}{I}}_0={\mathrm{\&Delta;}\stackrel{\&CenterDot;}{I}}_a+{\mathrm{\&Delta;}\stackrel{\&CenterDot;}{I}}_b+{\mathrm{\&Delta;}\stackrel{\&CenterDot;}{I}}_c$ , K is a setting value.

2. method according to claim 1 is characterized in that: setting value K is 0＜K＜1/3.

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