CN100388583C - Variable split-phase zero sequence fault component braking method for preventing transformer protection from malfunction - Google Patents

Abstract

The present invention discloses a variable phase-splitting braking method for preventing the malfunction of protection for transformers by utilizing zero sequence fault components; ratio braking elements are respectively composed of three-phase electric current fault components at the Y0 side of a transformer without zero sequence fault components and zero sequence electric current fault components at the side; when a ratio value is smaller than a definite value, a corresponding braking signal is output to stop differential protection for transformer ratios. The application of the proposal can thoroughly avoid the unwanted operation of differential protection for transformers caused by the 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 the conversion split-phase 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 conversion split-phase 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 conversion split-phase zero-sequence fault component braking method that prevents malfunction for tranformer protection is provided, with removing the transformer Y of zero-sequence component ₀The three-phase current fault component of side respectively with this side zero-sequence current fault component component ratio braking member, when rate value during, export the brake signal of corresponding phase less than setting value, the transformer ratio differential protection is braked, prevent the transformer differential protection malfunction.Advantage of the present invention is, relies on sudden change amount and this side zero-sequence current sudden change amount component ratio braking member of one-sided three-phase current, when avoiding the threephase current transformer error inconsistent fully, and Y ₀The transformer differential protection malfunction that lateral areas external ground fault causes.

A kind of conversion split-phase 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 three-phase current fault component of side is braked criterion with this side zero-sequence current fault component component ratio respectively, as the transformer Y that removes zero-sequence component ₀The three-phase current fault component of side during less than setting value, is exported the brake signal of corresponding phase divided by the rate value of this side zero-sequence current fault component, and the transformer ratio differential protection is braked; The foundation of conversion split-phase zero-sequence fault component braking is respectively:

$|\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{I}}_a-\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{I}}_0|/\left|\mathrm{\&Delta;}3{\stackrel{\&CenterDot;}{I}}_0\right|<K$

$|\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{I}}_b-\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{I}}_0|/\left|\mathrm{\&Delta;}3{\stackrel{\&CenterDot;}{I}}_0\right|<K$

$|\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{I}}_c-\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{I}}_0|/\left|\mathrm{\&Delta;}3{\stackrel{\&CenterDot;}{I}}_0\right|<K$

In the formula

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

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

For 1/3, setting value K 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 three-phase current fault component of side respectively with this side zero-sequence current fault component component ratio braking member, when rate value during, export the brake signal of corresponding phase less than setting value, the transformer ratio differential protection is braked, prevent 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 three-phase current fault component of side respectively with 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 conversion split-phase zero-sequence fault component braking element of malfunction for tranformer protection of the present invention.

Embodiment

Embodiment 1:

A kind of conversion split-phase 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 conversion split-phase 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 01～04,11～13, multiplier 21,22, filter 31～34 and comparator 41～43.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 output of subtracter 01～03 is connected with the positive input terminal of subtracter 11～13 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 connect an input of multiplier 21,22 respectively, another input input 1/3 of multiplier 21, another input input setting value K=0.2 of multiplier 22; The negative input end of subtracter 11～13 is connected with the output of multiplier 21, and its output connects the input of filter 31～33 respectively; The output of the input termination multiplier 22 of filter 34, its output connects the negative input end of comparator 41～43 respectively; The positive input terminal of comparator 41～43 connects the output of filter 31～33 respectively, and its output is exported the brake signal of A, B, C phase respectively.Positive input terminal signal in comparator is less than the negative input end signal, comparator output 0 is declared corresponding phase current for the error current that external ground fault in district's causes, exports corresponding phase brake signal, the transformer ratio differential protection is braked, prevented the transformer differential protection malfunction; Otherwise comparator output 1 allows corresponding phase differential protection action.Use this programme, only need to gather the Y that power supply is arranged ₀The three-phase current of side, with the three-phase current fault component of removing zero-sequence fault component respectively with zero-sequence current fault component component ratio braking member, 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.

Claims (2)

1. a conversion split-phase 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 three-phase current fault component of side is braked criterion with this side zero-sequence current fault component component ratio respectively, as the transformer Y that removes zero-sequence component ₀The three-phase current fault component of side during less than setting value, is exported the brake signal of corresponding phase divided by the rate value of this side zero-sequence current fault component, and the transformer ratio differential protection is braked; The foundation of conversion split-phase zero-sequence fault component braking is respectively:

$|\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{I}}_a-\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{I}}_0|/\left|\mathrm{\&Delta;}{3\stackrel{\&CenterDot;}{I}}_0\right|<K$

$|\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{I}}_b-\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{I}}_0|/\left|\mathrm{\&Delta;}{3\stackrel{\&CenterDot;}{I}}_0\right|<K$

$|\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{I}}_c-\mathrm{\&Delta;}{\stackrel{\&CenterDot;}{I}}_0|/\left|\mathrm{\&Delta;}{3\stackrel{\&CenterDot;}{I}}_0\right|<K$

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

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