CN100338472C - Zero sequence direction measurement method with zero sequence voltage compensation - Google Patents

Abstract

The present invention relates to a relay protection method in the electric power system field, and discloses a zero sequence direction judgment method by compensating for zero sequence voltages at the position of protection and installation. The method comprises the following steps that a high-voltage line protective device samples the waveforms of an electric current and a voltage of a transformer to obtain the instantaneous values of the electric current and the voltage; a complex form of each electric quantity is calculated by the Fu's algorithm; a zero sequence electric current and a zero sequence voltage are filtered at the position of protection and installation by a filtration algorithm. Firstly, the present invention judges whether a zero sequence electric current element satisfies conditions; secondly, the method judges whether the zero sequence voltage element is smaller than a definite value; if yes, a zero sequence voltage compensation element is put into service; the definite value is used as the necessary condition of the zero sequence voltage compensation element which is put into service. If the zero sequence direction element calculated by using the zero sequence voltage after compensation is in a headway direction, the zero sequence direction measured by the relay protection is headway. The method has accurate reorganization to the zero sequence direction when circuit high resistance has failures in grounding, and enhances the selectivity and the reliability of the zero sequence protection. The present invention enhances the sensibility of the zero sequence protection as well as ensures the safe and reliable running of the protection.

Description

Zero sequence direction measuring method with residual voltage compensation

Technical field

The present invention relates to field of power, relate more specifically to the method for relay protection.

Background technology

Transmission line of electricity is the basic equipment of electric system generating, conveying electricity etc., occupies important status in electric system.And transmission line of electricity often needs to pass through ground such as mountain area, plateau, frequent in recent years generation is owing to the high resistance earthing fault that branch, mao bamboon discharge and damage to crops caused by thunder, mountain fire are caused, bigger to main system influence, cause grid disconnection easily, and major accident such as transformer overstep tripping.High-voltage line protection is undertaken the vital task of carrying electricity, is the important pivot of electric system.Their costs are very expensive, damaged in case hinder for some reason, and the maintenance difficulty is big, the time is long, and the direct and consequential damage that national economy is caused is very huge.So just selectivity, rapidity, reliability, the sensitivity of high-voltage line protection device are had higher requirement.

For the high-voltage line protection of 220KV～750KV, because transmission range is long, the regional more complicated of circuit process tends to run into various forms of faults, in recent years since the phenomenon of the protection tripping that high resistance earthing fault causes happen occasionally.When high resistant discontinuity earth fault takes place when, owing to there is stray voltage, cause that circuit microcomputer carrier current protection can not in time move outlet, the scope that causes power failure is the accident of expansion further, has had a strong impact on safe operation.For high resistive fault; the way that solves mainly is to come would trip by reserve zero-sequenceprotection at present; and high pressure zero-sequenceprotection will guarantee selectivity, reliability; then need zero sequence direction accurately to declare zero sequence pros always to check on; guarantee only when the protection domain internal fault; this protective device just can move, and protects akinesia in the other direction.Zero sequence direction mainly is just to think in the positive dirction of protection fault to have taken place in a certain scope by the phase angle difference that compares between residual voltage and the zero-sequence current at present, then thinks reverse direction failure at other angular range.

At present traditional zero-sequence direction component criterion is as follows: during greater than certain numerical value, criterion is as follows at residual voltage and zero-sequence current:

$D_{3I0}=3{\stackrel{\·}{U}}_0/3{\stackrel{\·}{I}}_0$

3  in the formula ₀,

Be respectively the residual voltage of protection installation place, zero-sequence current.

For protection TA (current measurement device); TV (voltage measurement element); certain range accuracy is arranged; error as 10%; to measuring sensor is to allow it that error is arranged; this just requires when residual voltage and zero-sequence current during less than certain numerical value; do not allow protection to declare direction; the little then zero-sequenceprotection of zero-sequence current elemental motion condition does not satisfy, then akinesia, and on-the-spot ruuning situation shows; when high resistance earthing fault; the zero-sequence current condition generally can both satisfy the operation condition of zero-sequenceprotection, and residual voltage is because the earth point difference often can not satisfy accuracy requirement when high resistance ground.The present invention is directed to present high resistance ground residual voltage condition and can not satisfy the problem that the requirement of declaring zero sequence direction exists, proposes a kind of algorithm that voltage of zero sequence voltage component is carried out compensation with good conditionsi, satisfy the requirement of calculating zero sequence direction.

Summary of the invention

For high resistance earthing fault; the zero sequence measuring voltage of protection installation place may be lower; residual voltage can not satisfy the problem of the precision of declaring zero sequence direction; the invention provides a kind of by voltage of zero sequence voltage component is effectively compensated; thereby improved the residual voltage numerical value under the positive dirction ground fault condition, thereby satisfied the condition of the residual voltage of declaring zero sequence direction.After adopting the present invention, can effectively solve this type of problem.This method comprises the steps: that line protective devices are sampled to the current-voltage waveform of mutual inductor and obtains the current/voltage instantaneous value; Obtain the plural form of each electric parameters by fourier algorithm; Leach the zero-sequence component of electric current and voltage by strain sequence arithmetic; If residual voltage greater than the threshold value that calculates zero sequence direction, then calculates zero sequence direction by normal method; If residual voltage less than the residual voltage threshold value that calculates zero sequence direction, then compares with residual voltage and residual voltage threshold value after the compensation, as if greater than, then carry out the direction calculating of zero sequence component.This method is more accurate to the identification of high resistance earthing fault, can guarantee the safe and reliable operation protected when improving sensitivity, when having solved for a long time high resistance earthing fault preferably, and the technical barrier that existing protection can not correct operation.

Description of drawings

Accompanying drawing 1 is the logic diagram of zero sequence compensation directional element.

Specific embodiments

Symbol in below discussing uses as follows: current transformer (being called for short TA, as follows) and voltage transformer (VT) (being called for short TV, as follows).

At first protect according to the TA of protection installation place and the instantaneous value that TV records electric current and voltage.

Secondly obtain the plural form of each electric parameters by fourier algorithm, can leach the real part 3I of the zero-sequence current of protection installation place then by the strain sequence arithmetic shown in the following formula _0ReWith imaginary part 3I _0Im Real part 3U with residual voltage _0ReWith imaginary part 3U _0Im:

3I _0Re＝I _aRe+I _bRe+I _cRe

3I _0Im＝I _aIm+I _bIm+I _cIm (1)

3U _0Re＝3U _aRe+3U _bRe+3U _cRe

3U _0Im＝U _aIm+U _bIm+U _cIm

In the formula: 3I _0Re, 3I _0Im, 3U _0Re, 3U _0ImBe respectively the real part and the imaginary part of zero-sequence current, the real part of residual voltage and imaginary part, I _ARe, I _AIm, I _BReI _BIm, I _CRe, I _CIm, U _ARe, U _AIm, U _BReU _BIm, U _CRe, U _CImBe respectively A, B, the real part of C phase current and voltage and imaginary part.

Whether the protection logical diagram of Xian Shiing with reference to the accompanying drawings, protection adopt self-produced zero-sequence current and residual voltage to calculate zero sequence direction, compensate according to the difference decision of the size of residual voltage.If the residual voltage that residual voltage less than the residual voltage threshold value, then uses following formula to calculate replaces former residual voltage:

$3{\stackrel{\·}{U}}_0^{\′}=3{\stackrel{\·}{U}}_0-Z_0*3{\stackrel{\·}{I}}_0---\left(2\right)$

In the formula: 3  ' ₀, 3  ₀,

Z ₀Be respectively the residual voltage after the compensation, the residual voltage of former protection measured place, the zero-sequence current of protection measured place, the zero sequence impedance of protection circuit.

The maximum sensitive angle of zero sequence direction is generally 75 °～85 ° of the leading residual voltages of zero-sequence current.

Make comparisons with threshold value again with this residual voltage value that recalculates, if then utilize following formula to carry out the calculating of zero sequence direction greater than threshold value:

$D_{3I0}=(3{\stackrel{\·}{U}}_0-3{\stackrel{\·}{I}}_0*Z_0)/3{\stackrel{\·}{I}}_0$

In the formula: D _3I0For calculating the zero sequence direction obtained,

If the zero sequence direction D after the compensation _3I0Satisfy the requirement of positive dirction, then allow zero-sequenceprotection to trip.

Residual voltage after wherein employing compensates carries out the zero sequence direction The conditions of calculation and can provide with following formula:

$({3U}_0<U_{0\mathrm{MK}})\&cap;(\left(\right|3{\stackrel{\&CenterDot;}{U}}_0-Z_0*3{\stackrel{\&CenterDot;}{I}}_0\left|\right)>U_{0\mathrm{MK}})$

In the formula: Z ₀Be the zero sequence impedance value of circuit,

3  ₀Be respectively zero-sequence current and residual voltage that protection is surveyed, U _0MKFor whether using the threshold of zero sequence compensation element.

The 1 protection logical diagram that shows with reference to the accompanying drawings; all do not take place under the unusual situation at TA and TV; if have zero-sequence current and residual voltage; and zero-sequence current is greater than threshold value; so, during greater than the residual voltage threshold, use traditional residual voltage to calculate zero sequence direction at residual voltage; if residual voltage is lower than the residual voltage threshold value, then calculate zero sequence direction with the residual voltage after the compensation.

When the protection circuit internal faults takes place when, the residual voltage of protection installation place may be smaller, the transition resistance at fault place is big more, the residual voltage of protection installation place is more little, at present, high resistive fault took place in many places, by theoretical analysis as can be known, residual voltage can satisfy the requirement of the voltage that calculates zero sequence direction after calculating through compensation; But when the secondary circuit broken string takes place in TV, since influential to calculating residual voltage, when the secondary circuit broken string taking place, influential to calculating zero-sequence current as if TA.Therefore if the secondary circuit broken string all takes place for TA and TV, or external area error takes place during some broken strings again, then may cause the malfunction of this protection, therefore when protecting when declaring to have taken place TA or TV and breaking, with this protection of locking.

In fact, in the external area error transient state process of complexity, for example when the outer near terminal fault in district, the residual voltage that protection is surveyed can satisfy condition, and therefore when reverse fault, this direction element can misoperation.When phase-to phase fault takes place,, there is not zero-sequence current simultaneously, so this element misoperation can not take place yet owing to there is not residual voltage yet.

In sum; the present invention is at residual voltage during less than the residual voltage threshold value; residual voltage is effectively compensated, and calculate zero sequence direction, when improving sensitivity, can guarantee the safe and reliable operation of protective device with residual voltage after the compensation and zero-sequence current.

Claims (2)

1. method of judging zero sequence direction in the ultra-high-tension power transmission line zero-sequenceprotection of electric system, this method comprises the steps:

Line protective devices obtain the current/voltage instantaneous value to the current-voltage waveform sampling of mutual inductor;

Obtain the plural form of each electric parameters by fourier algorithm;

Leach the zero-sequence component of electric current and voltage by strain sequence arithmetic;

It is characterized in that:

If residual voltage greater than threshold value, then calculates zero sequence direction by normal method;

If the residual voltage value calculated less than threshold value, then utilizes value that a calculating formula recomputates residual voltage by way of compensation, replace the value of former residual voltage;

Described calculating formula is: $3{\stackrel{\&CenterDot;}{U}}_0^{\&prime;}={3\stackrel{\&CenterDot;}{U}}_0-Z_0*3{\stackrel{\&CenterDot;}{I}}_0$

In the formula:

Z ₀Be respectively the residual voltage after the compensation, the residual voltage of former protection measured place, the zero-sequence current of protection measured place, the zero sequence impedance of protection circuit;

Make comparisons with threshold value again with this residual voltage value that recalculates, if then utilize following formula to carry out the calculating of zero sequence direction greater than threshold value:

$D_{3I0}=(3{\stackrel{\&CenterDot;}{U}}_0-{3\stackrel{\&CenterDot;}{I}}_0*Z_0)/3{\stackrel{\&CenterDot;}{I}}_0$

In the formula: D _3I0For calculating the zero sequence direction obtained,

If the zero sequence direction D after the compensation ₃₁₀Satisfy the requirement of positive dirction, then allow zero-sequenceprotection to trip.

2. method as claimed in claim 1, the residual voltage after wherein employing compensates carries out the zero sequence direction The conditions of calculation and can provide with following formula:

$(3U_0<U_{0\mathrm{MK}})\&cap;(\left(\right|3{\stackrel{\&CenterDot;}{U}}_0-Z_0*3{\stackrel{\&CenterDot;}{I}}_0\left|\right)>U_{0\mathrm{MK}})$

In the formula: Z ₀Be the zero sequence impedance value of circuit,

Be respectively zero-sequence current and residual voltage that protection is surveyed, U _OMKFor whether using the threshold of zero sequence compensation element.

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