CN100350708C - Maximum changing carrent zero-sequence fault component braking method for preventing malfunction for transformer protection - Google Patents

Abstract

The present invention discloses a maximum changing electric current zero-sequence fault component braking method for preventing the malfunction of protection for transformers; ratio braking elements are composed of the maximum value of fault components of a three-phase electric current at the Yo side of a transformer removing zero-sequence components and the fault components of a zero-sequence electric current 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 elements composed of the maximum value of the fault components of a three-phase electric current at the Yo side of the transformer removing zero-sequence components and the fault components of a zero-sequence electric current 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 imbalance electric currents under the condition of other non-internal faults.

Description

Prevent the maximum conversion current zero sequence fault component braking method of malfunction for tranformer protection

Technical field

The present invention relates to a kind of relay protection method of power system, particularly a kind of maximum conversion current zero sequence fault component braking method that prevents malfunction for tranformer 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; 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, and a kind of maximum conversion current zero sequence fault component braking method that prevents malfunction for tranformer protection is provided, with removing the transformer Y of zero-sequence component ₀The maximum of the three-phase current fault component of side and this side zero-sequence current fault component component ratio braking member, when rate value during less than setting value, the output brake signal is braked the transformer ratio differential protection, prevents the transformer differential protection malfunction.Advantage of the present invention is to rely on the maximum of one-sided three-phase current sudden change amount and this side zero-sequence current sudden change amount component ratio to brake when avoiding the threephase current transformer error inconsistent fully Y ₀The transformer differential protection malfunction that lateral areas external ground fault causes.

A kind of maximum conversion current zero sequence fault component braking method that prevents malfunction for tranformer protection is characterized in that: with removing the transformer Y of zero-sequence component ₀The maximum of the three-phase current fault component of side and this side zero-sequence current fault component component ratio braking member are removed the transformer Y of zero-sequence component when using ₀During less than setting value K, brake the transformer ratio differential protection by the output brake signal divided by the rate value of this side zero-sequence current fault component for the maximum of the three-phase current fault component of side; The foundation of maximum conversion current zero sequence fault component braking is:

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

In the formula

Be respectively transformer Y ₀The three-phase current fault component vector of side,

For removing the transformer Y of zero-sequence component ₀The maximum of the three-phase current fault component of side, Be this side zero-sequence current fault component vector, promptly $\mathrm{\Δ}3{\stackrel{\·}{I}}_0=\mathrm{\Δ}{\stackrel{\·}{I}}_a+\mathrm{\Δ}{\stackrel{\·}{I}}_b+\mathrm{\Δ}{\stackrel{\·}{I}}_c,$

For

1/3, K is a setting value, 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 with removing the transformer Y of zero-sequence component ₀The maximum of the three-phase current fault component of side and this side zero-sequence current fault component component ratio braking member, when rate value during less than setting value, the output brake signal is braked the transformer ratio differential protection, prevents 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 with removing the transformer Y of zero-sequence component ₀The maximum of the corresponding phase of 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 a kind of circuit block diagram that prevents the maximum conversion current zero sequence fault component braking element of malfunction for tranformer protection of the present invention.

Embodiment

Embodiment 1:

A kind of maximum conversion current zero sequence fault component braking method that prevents the transformer differential protection malfunction, this method can be achieved by a kind of circuit block diagram of the maximum conversion current zero sequence fault component braking element of malfunction for tranformer protection that prevents of Fig. 1.This element is made of memory 1～4, subtracter 01～04, subtracter 11～13, multiplier 21,22, filter 31～34, maximizing circuit 41 and comparator 42.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; The positive input terminal of subtracter 11～13 is connected with the output of subtracter 01～03 respectively, and its output connects the input of filter 31～33 respectively; The output of filter 31～33 is connected with three inputs of maximizing circuit 41 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 are connected with an input of multiplier 21,22 respectively; Another input input 1/3 of multiplier 21, its output connects the negative input end of subtracter 11～13 respectively; Another input input setting value K=0.3 of multiplier 22, its output is connected with the input of filter 34; The negative input end of the output termination comparator 42 of filter 34; The positive input terminal of comparator 42 is connected with the output of maximizing circuit 41, its output output three-phase brake signal.Positive input terminal signal in comparator is less than the negative input end signal, and 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 Y that power supply is arranged ₀The three-phase current of side is with removing the transformer Y of zero-sequence component ₀The ratio brake element that the maximum of the three-phase current fault component of side and this side zero-sequence current fault component constitute, 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.

Claims (2)

1. a maximum conversion current zero sequence fault component braking method that prevents malfunction for tranformer protection is characterized in that: with removing the transformer Y of zero-sequence component ₀The maximum of the three-phase current fault component of side and this side zero-sequence current fault component component ratio braking member are removed the transformer Y of zero-sequence component when using ₀During less than setting value, brake the transformer ratio differential protection by the output brake signal divided by the rate value of this side zero-sequence current fault component for the maximum of the three-phase current fault component of side; The foundation of maximum conversion current zero sequence fault component braking is:

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

In the formula

Be respectively transformer Y ₀The three-phase current fault component vector of side,

For removing the transformer Y of zero-sequence component ₀The maximum of the three-phase current fault component of side,

Be this side zero-sequence current fault component vector, promptly

For

1/3, 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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