CN1870376A - Method for correct identificating paradrop excitation surge and paradrop fault in transformer protection - Google Patents

Abstract

This invention relates to a method for identifying air excitation flow and airdrop faults correctly in the protection of high voltage transformers, which selects two watching windows at current waveforms, then utilizes the current in one of the windows to forecast a sine wave, utilizes the probability theory to compute the relative coefficient of the sine wave sequence and that of the windows to differentiate airdrop transformers and the fault ones by the relative coefficient to reach the aim of quickly excising the fault air transformers.

Description

Correct identification air-drop magnetizing inrush current and the method for dropping fault in the tranformer protection

Technical field

The present invention relates to correctly discern in a kind of tranformer protection in the electricity field tranformer protection air-drop magnetizing inrush current and the method for dropping fault

Background technology

Correct identification magnetizing inrush current is an important indicator weighing high pressure, superhigh pressure voltage grade transformer differential protection; because jumbo transformer magnetizing inrush current when air-drop is little; differential protection is reliably motionless in order to guarantee to drop; it is very little generally secondary harmonic brake coefficient in the differential protection to be adjusted, and with " or " closedown mode.So just cause in air-drop during failure transformer and since the magnetizing inrush current locking of non-fault phase the fault phase, the differential protection responsiveness was slow when this just caused dropping failure transformer, brought hidden danger for the safe operation of transformer.

Summary of the invention

At the problems referred to above; the object of the present invention is to provide correct identification air-drop magnetizing inrush current and the method for dropping fault in a kind of tranformer protection; characteristics when utilizing the air-drop failure transformer, clear failure is mutually differential fast, reaches the QA purpose of differential protection.

To achieve the above object of the invention, technical scheme of the present invention is:

Correct identification air-drop magnetizing inrush current and the method for dropping fault in a kind of tranformer protection, the step of this method is as follows:

(1) the definite observation window that will sample, its method is as follows:

Observation window 1:

At first find the value of the interior sampled point maximum of one-period in the difference stream waveform, and then find the maximum value of previous periodic sampling point, two interior zones of maximum are observation window 1;

Observation window 2:

In observation window 1, look for the negative maximum 2 opposite, get the n point respectively as observation window 2 in the front and back of maximum 2 then with maximum 1;

(2) a virtual half cycle sine wave

Is reference waveform with peaked absolute value in the observation window 2 as the virtual identical half cycle sine wave of waveform half cycle tendency of the amplitude of sine wave;

(3) determine operating criterion

With observation window 2 is an ordered series of numbers X, is ordered series of numbers Y with the sine wave of predicting, relatively the coefficient correlation of ordered series of numbers X, Y;

$\mathrm{\β}(X,Y)=\frac{\mathrm{Cov}(X,Y)}{\mathrm{\σ}\left(X\right)\mathrm{\σ}\left(Y\right)}$

Following formula:

Cov(XY)＝E(XY)-E(X)E(Y)

$\mathrm{\σ}\left(X\right)=\sqrt{\underset{k=1}{\overset{n}{\mathrm{\Σ}}}{(X_k-E\left(X\right))}^2}$

$\mathrm{\σ}\left(Y\right)=\sqrt{\underset{k=1}{\overset{n}{\mathrm{\Σ}}}{(Y_k-E\left(Y\right))}^2}$

If:

β (X, Y)＜k then is judged as the normal transformer of air-drop, this phase differential protection of locking; (K is an inner definite value that is provided with, and generally gets 0.6-0.8)

β (X, Y)＞k then is judged as the air-drop failure transformer, open this phase differential protection.

In order to improve the reliability that this declares a tree name, set up two start-up criterion, satisfy at the same time under the condition of three criterions, open this phase differential protection, its logic diagram is as follows:

Among the figure: I is the effective value of this phase current; Ie is a rated current; i _kBe the maximum in the observation window 2.

The present invention does not carry out angular transition, has kept the original useful information of sample waveform, predicts that simultaneously a sinusoidal wave function and original waveform analyze.Utilization re-constructs sinusoidal wave method, and the sampled point of extraction and the sine wave of prediction are analyzed, and reaches the purpose of quick excision air-drop failure transformer.

Major measure can reduce:

A. analyzed the waveform that drops normal transformer and air-drop failure transformer;

B., the system of selection of observation window is proposed, and the method for sampling in the proposition analysis waveform;

C. predict a sinusoidal wave function;

D. utilize the probability theory theory that sampling is analyzed;

E. utilize phase current to start the reliability that improves this principle.

Description of drawings

Fig. 1 is the normal transformer oscillogram of air-drop;

Fig. 2 is air-drop failure transformer oscillogram.

Embodiment

Following mask body is narrated detailed content of the present invention:

Principle analysis

When dropping normal transformer, difference stream waveform be the waveform that shoves, because the influence of the angle of voltage when the size of transformer remanent magnetism, direction and combined floodgate causes the waveform that shoves of transformer can not determine, the waveform that still shoves has tangible interval angle.Also might cause TA saturated during the air-drop transformer, cause waveform symmetrical up and down sometimes, but the saturated waveform of TA transient state have platform area about time shaft.Air-drop failure transformer time difference stream waveform is the stack of magnetizing inrush current waveform and fault current waveform, but whether simply superposes.When transformer core was operated in the saturation region, current waveform had the characteristics of the waveform that shoves, when transformer core is operated in the unsaturation district, because the influence of fault current has sinusoidal wave feature.This programme utilizes this feature to discern normal transformer of air-drop and air-drop failure transformer exactly.Reach the purpose of quick excision failure transformer.

1, the methods of sampling

At first find the observation window that will sample, its method is as follows:

Observation window 1:

At first find the value of the interior sampled point maximum of one-period in the waveform, and then find the maximum value of previous periodic sampling point, two interior zones of maximum are observation window 1;

Observation window 2:

In observation window 1, look for the negative maximum 2 opposite, get the n point respectively as observation window 2 in the front and back of maximum 2 then with maximum 1;

Virtual sine wave:

Predict that as the amplitude of sine wave a half cycle sine wave is a reference waveform with peaked absolute value in the observation window 2.The process accompanying drawing of said method.

2, operating criterion

With observation window 2 is an ordered series of numbers X, is ordered series of numbers Y with the sine wave of predicting, relatively the coefficient correlation of ordered series of numbers X, Y;

$\mathrm{\β}(X,Y)=\frac{\mathrm{Cov}(X,Y)}{\mathrm{\σ}\left(X\right)\mathrm{\σ}\left(Y\right)}$

Following formula:

Cov(XY)＝E(XY)-E(X)E(Y)

$\mathrm{\σ}\left(X\right)=\sqrt{\underset{k=1}{\overset{n}{\mathrm{\Σ}}}{(X_k-E\left(X\right))}^2}$

$\mathrm{\σ}\left(Y\right)=\sqrt{\underset{k=1}{\overset{n}{\mathrm{\Σ}}}{(Y_k-E\left(Y\right))}^2}$

If:

β (X, Y)＜k then is judged as the normal transformer of air-drop, this phase differential protection of locking; (K is an inner definite value that is provided with, and generally gets 0.6-0.8)

β (X, Y)＞k then is judged as the air-drop failure transformer, open this phase differential protection.

3, action element logic diagram

In order to improve the reliability that this declares a tree name, set up two startups and declare a tree name, satisfy at the same time under the condition of three criterions, open this phase differential protection, its logic diagram is as follows:

Among the figure: I is the effective value of this phase current; Ie is a rated current; i _kBe the maximum in the observation window 2.

Claims (2)

1, correct identification air-drop magnetizing inrush current and the method for dropping fault in a kind of tranformer protection is characterized in that the step of this method is as follows:

(1) the definite observation window that will sample, its method is as follows:

Observation window 1:

At first find the value of the interior sampled point maximum of one-period in the difference stream waveform, and then find the maximum value of previous periodic sampling point, two interior zones of maximum are observation window 1;

Observation window 2:

In observation window 1, look for the negative maximum 2 opposite, get the n point respectively as observation window 2 in the front and back of maximum 2 then with maximum 1;

(2) a virtual half cycle sine wave:

Is reference waveform with peaked absolute value in the observation window 2 as the virtual identical half cycle sine wave of waveform half cycle tendency of the amplitude of sine wave;

(3) determine operating criterion

With observation window 2 is an ordered series of numbers X, is ordered series of numbers Y with the sine wave of predicting, relatively the coefficient correlation of ordered series of numbers X, Y;

$\mathrm{\β}(X,Y)=\frac{\mathrm{Cov}(X,Y)}{\mathrm{\σ}\left(X\right)\mathrm{\σ}\left(Y\right)}$

Following formula:

Cov(XY)＝E(XY)-E(X)E(Y)

$\mathrm{\σ}\left(X\right)=\sqrt{\underset{k=1}{\overset{n}{\mathrm{\Σ}}}{(X_k-E\left(X\right))}^2}$

$\mathrm{\σ}\left(Y\right)=\sqrt{\underset{k=1}{\overset{n}{\mathrm{\Σ}}}{(Y_k-E\left(Y\right))}^2}$

If:

β (X, Y)＜k then is judged as the normal transformer of air-drop, this phase differential protection of locking; (K is an inner definite value that is provided with, and generally gets 0.6-0.8)

β (X, Y)＞k then is judged as the air-drop failure transformer, open this phase differential protection.

2, correct identification air-drop magnetizing inrush current and the method for dropping fault in the tranformer protection according to claim 1; it is characterized in that; in order to improve the reliability that this declares a tree name; set up two start-up criterion; satisfy under the condition of three criterions at the same time; open this phase differential protection, its logic diagram is as follows:

Among the figure: I is the effective value of this phase current; Ie is a rated current; i _kBe the maximum in the observation window 2.

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