CN103346541A - Convertor station direct current filter differential protection method and device - Google Patents

Abstract

The invention relates to a convertor station direct current filter differential protection method and device. The convertor station direct current filter differential protection device firstly acquires the current on the high voltage side of a direct current filter and the current on the low voltage side of the direct current filter, calculates the difference value of the currents, and then conducts logical judgment and processing according to protection logic. The convertor station direct current filter differential protection method can judge a failure quickly and accurately, and the risks of protection maloperations or protection failures due to the fact that a current transformer is saturated and measurement distortion occurs are avoided when a failure occurs.

Description

Current conversion station DC filter differential protecting method and device

Technical field

The present invention relates to method and the fixed value adjusting of a kind of DC filter differential protection in a kind of high voltage direct current transmission project, be applicable to high voltage direct current transmission DC filter protection system.

Background technology

DC filter is the visual plant in the HVDC (High Voltage Direct Current) transmission system, in current conversion station, is between the bus of DC side, and as shown in Figure 1, the DC filter two ends are connected to high voltage bus and neutral bus every cutter and low-pressure side every cutter by the high-pressure side respectively.

The DC filter differential protection is the main protection in the DC filter protection, the defencive function when realizing the DC filter internal ground fault.The DC filter differential protection is gathered the current signal of the on high-tension side current signal of DC filter and low-pressure side, protects the zone between two measuring points, and two measuring points are respectively current transformer T1 and T4 among Fig. 1.When earth fault took place in its protection zone, the electric current of both sides had very big difference, when this difference during greater than the action definite value, through certain time-delay output protection actuating signal, drew back the DC filter high-pressure side every cutter or stoppage in transit HVDC (High Voltage Direct Current) transmission system.

Existing DC filter differential protecting method, employing be: the electric current difference is greater than a fixing definite value, through output protection actuating signal after the long time-delay; But when breaking down, a large amount of direct currents is often flow through in the fault point, and the magnetic saturation phenomenon can take place current transformer, causes the measurement distortion, and there is the risk of protection malfunction and tripping in the DC filter differential protection.

Summary of the invention

The purpose of this invention is to provide a kind of DC filter differential protecting method, in order to solve the problem that existing guard method exists malfunction and tripping hidden danger.

For achieving the above object, the solution of the present invention comprises:

Current conversion station DC filter differential protecting method is characterized in that step is as follows:

1) gathers DC filter high voltage side current signal IT1 and low-pressure side current signal IT4, and calculate electric current difference DIF according to the current signal of gathering;

2) carry out differential protection and judge that criterion is DIF＞Δ+K*IT1 _Rms, Δ is the constant definite value, K is ratio brake coefficient, IT1 _RmsEffective value for high voltage side current;

When 3) satisfying described criterion, the protection action.

The DC filter differential protection is divided into three sections, every section protection definite value, time-delay and action policy that has separately, and the criterion of three sections correspondences, time-delay and action policy are respectively:

(1) DIF＞Δ 1+K1*IT1 _Rms﹠amp; IT1 _Rms＜Δ; Time-delay T1; Action policy: draw back the DC filter high-pressure side every cutter; Δ is that the high-pressure side is every cutter arcing ability set point; Δ 1 is first section and the second segment protect definite value, and K1 is first section and second section ratio brake coefficient, and T1 is first section and second section action delay;

(2) DIF＞Δ 1+K1*IT1 _Rms﹠amp; IT1 _Rms＞Δ; Time-delay T1; Action policy: send out phase shift locking order to utmost point control system, stoppage in transit HVDC (High Voltage Direct Current) transmission system, the AC circuit breaker of tripping simultaneously, startup breaker fail protection;

(3) DIF＞Δ 2+K2*IT1 _RmsTime-delay T2; Action policy: send out phase shift locking order to utmost point control system, stoppage in transit HVDC (High Voltage Direct Current) transmission system, the AC circuit breaker of tripping simultaneously, startup breaker fail protection; Δ 2 is the three section protection definite value, and K2 is the 3rd section ratio brake coefficient, and T2 is the 3rd period operate time.

The high-pressure side is determined every the arcing ability of cutter by primary equipment DC filter high-pressure side every cutter arcing ability set point Δ; Three section protection definite value Δ 2, the 3rd section ratio brake coefficient K2 and the 3rd section action delay T2 according to DC filter and high-pressure side the short circuit trouble point (F1) between cutter determine; First section and the second segment protect definite value Δ 1, first section and second section ratio brake coefficient K1 and first section and second section action delay T1 according to DC filter internal short circuit fault point and and the short circuit trouble point (F2, F3, F4) of low-pressure side between cutter determine.

In the step 1),

Wherein N is the sampling number in a power frequency period, and K is the setting coefficient,

Be the mean value of the interior IT1 of a power frequency period and IT4 difference. ${\mathrm{IT}1}_{\mathrm{rms}}=\frac{\sqrt{\underset{1}{\overset{N}{\mathrm{\Σ}}}\mathrm{IT}{1}^2}}{N}.$

Current conversion station DC filter differential protection is characterized in that, comprising:

1) acquisition elements: gather DC filter high voltage side current signal IT1 and low-pressure side current signal IT4, and calculate electric current difference DIF according to the current signal of gathering;

2) judgment component: carry out differential protection and judge that criterion is DIF＞Δ+K*IT1 _Rms, Δ is the constant definite value, K is ratio brake coefficient, IT1 _RmsEffective value for high voltage side current;

3) executive component: when satisfying described criterion, the protection action.

The DC filter differential protection is divided into three sections, every section protection definite value, time-delay and action policy that has separately, and the criterion of three sections correspondences, time-delay and action policy are respectively:

(1) DIF＞Δ 1+K1*IT1 _Rms﹠amp; IT1 _Rms＜Δ; Time-delay T1; Action policy: draw back the DC filter high-pressure side every cutter; Δ is that the high-pressure side is every cutter arcing ability set point; Δ 1 is first section and the second segment protect definite value, and K1 is first section and second section ratio brake coefficient, and T1 is first section and second section action delay;

(2) DIF＞Δ 1+K1*IT1 _Rms﹠amp; IT1 _Rms＞Δ; Time-delay T1; Action policy: send out phase shift locking order to utmost point control system, stoppage in transit HVDC (High Voltage Direct Current) transmission system, the AC circuit breaker of tripping simultaneously, startup breaker fail protection;

(3) DIF＞Δ 2+K2*IT1 _RmsTime-delay T2; Action policy: send out phase shift locking order to utmost point control system, stoppage in transit HVDC (High Voltage Direct Current) transmission system, the AC circuit breaker of tripping simultaneously, startup breaker fail protection; Δ 2 is the three section protection definite value, and K2 is the 3rd section ratio brake coefficient, and T2 is the 3rd period operate time.

The high-pressure side is determined every the arcing ability of cutter by primary equipment DC filter high-pressure side every cutter arcing ability set point Δ; Three section protection definite value Δ 2, the 3rd section ratio brake coefficient K2 and the 3rd section action delay T2 according to DC filter and high-pressure side the short circuit trouble point (F1) between cutter determine; First section and the second segment protect definite value Δ 1, first section and second section ratio brake coefficient K1 and first section and second section action delay T1 according to DC filter internal short circuit fault point and and the short circuit trouble point (F2, F3, F4) of low-pressure side between cutter determine.

In the step 1), Wherein N is the sampling number in a power frequency period, and K is the setting coefficient, Be the mean value of the interior IT1 of a power frequency period and IT4 difference. ${\mathrm{IT}1}_{\mathrm{rms}}=\frac{\sqrt{\underset{1}{\overset{N}{\mathrm{\Σ}}}\mathrm{IT}{1}^2}}{N}.$

DC filter differential protecting method of the present invention; the operating current of differential protection no longer is definite value; but adopt constant to add the novel criterion of ratio brake; and ratio brake is relevant with high voltage side current; weaken the measurement influence that magnetic saturation causes, thereby reduced the risk of differential protection malfunction and tripping.

Further, method of the present invention has also adopted the strategy of protection segmentation, and the DC filter differential protection is divided into three sections, every section have different protection definite value and corresponding time-delay, action is measured, and makes protection more accurately reliable.

At last, method of the present invention gives the measure of adjusting of definite value.Use method of the present invention, failure judgement quickly and accurately, saturated the causing of current transformer is measured the risk that distortion makes protection malfunction or tripping when avoiding fault.

Description of drawings

Fig. 1 is the DC filter winding diagram;

Fig. 2 is the differential protecting method logic diagram of embodiment 2;

Fig. 3 is the critical failure point schematic diagram of DC filter differential protection fixed value adjusting.

Embodiment

The present invention will be further described in detail below in conjunction with accompanying drawing.

The present invention's current conversion station DC filter required for protection differential protection is interpreted as the function module member based on differential protecting method of the present invention, is not entity apparatus, so hereinafter omitted device embodiment.The present invention can control platform or the PC device is realized with built-in industrial, and these two kinds of devices are high-voltage dc transmission electrical domain devices commonly used.

The exemplary block diagram of DC filter and differential protection electric current measuring point, as shown in Figure 1.It is installed in the middle of high direct voltage bus and the DC bus, and its structure is made up of elements such as high end capacitor and low side resistance, inductance; Measuring point is mainly high pressure and surveys electric current I T1, low pressure survey electric current I T4.

Embodiment 1

According to method of the present invention, at first gather DC filter high voltage side current signal IT1 and low-pressure side current signal IT4, and calculate electric current difference DIF according to the current signal of gathering; Carry out differential protection then and judge that criterion is DIF＞Δ+K*IT1 _Rms, Δ is the constant definite value, K is ratio brake coefficient, IT1 _RmsEffective value for high voltage side current; When satisfying described criterion, the protection action.

As a kind of DIF and IT1 _RmsAccount form,

Wherein N is the sampling number in a power frequency period, and K is the setting coefficient,

Be the mean value of the interior IT1 of a power frequency period and IT4 difference,

Embodiment 2

In order to implement protection better, protect segmentation: the DC filter differential protection is divided into three sections, and every section has different protection definite values and reaches corresponding time-delay, action policy.Corresponding criterion, time-delay and action policy are respectively:

(1) DIF＞Δ 1+K1*IT1 _Rms﹠amp; IT1 _Rms＜Δ; Time-delay T1; Action policy: draw back the DC filter high-pressure side every cutter; Δ is that the high-pressure side is every cutter arcing ability set point; Δ 1 is first section and the second segment protect definite value, and K1 is first section and second section ratio brake coefficient, and T1 is first section and second section action delay; ﹠amp; Be logical AND.

(2) DIF＞Δ 1+K1*IT1 _Rms﹠amp; IT1 _Rms＞Δ; Time-delay T1; Action policy: send out phase shift locking order to utmost point control system, stoppage in transit HVDC (High Voltage Direct Current) transmission system, the AC circuit breaker of tripping simultaneously, startup breaker fail protection;

(3) DIF＞Δ 2+K2*IT1 _RmsTime-delay T2; Action policy: send out phase shift locking order to utmost point control system, stoppage in transit HVDC (High Voltage Direct Current) transmission system, the AC circuit breaker of tripping simultaneously, startup breaker fail protection; Δ 2 is the three section protection definite value, and K2 is the 3rd section ratio brake coefficient, and T2 is the 3rd period operate time.

Adjusting according to the result of dynamic performance testing of protection definite value; under the situation that DC component increases in the time of will considering fault especially during test; this moment, the current transformer measurement result will distortion; so should carry out the DCO of each fault point putting (under the failure condition) before this, guarantee that further defencive function can correct operation under various operating conditions.Critical failure point F1, F2, F3, the F4 of DC filter differential protection fixed value adjusting, as shown in Figure 3.The definite value of each segment protect and the coefficient of ratio are determined by the dynamic performance testing result among the present invention; the principle of adjusting is can action message according to earth fault time protection in the district; pass through the formula electric current when preventing external area error and cause the protection malfunction, to determine protection action definite value, ratio brake coefficient and action delay.

Claims (10)

1. current conversion station DC filter differential protecting method is characterized in that, step is as follows:

1) gathers DC filter high voltage side current signal IT1 and low-pressure side current signal IT4, and calculate electric current difference DIF according to the current signal of gathering;

2) carry out differential protection and judge that criterion is DIF＞Δ+K*IT1 _Rms, Δ is the constant definite value, K is ratio brake coefficient, IT1 _RmsEffective value for high voltage side current;

When 3) satisfying described criterion, the protection action.

2. current conversion station DC filter differential protecting method according to claim 1; it is characterized in that; the DC filter differential protection is divided into three sections, every section protection definite value, time-delay and action policy that has separately, and the criterion of three sections correspondences, time-delay and action policy are respectively:

(1) DIF＞Δ 1+K1*IT1 _Rms﹠amp; IT1 _Rms＜Δ; Time-delay T1; Action policy: draw back the DC filter high-pressure side every cutter; Δ is that the high-pressure side is every cutter arcing ability set point; Δ 1 is first section and the second segment protect definite value, and K1 is first section and second section ratio brake coefficient, and T1 is first section and second section action delay;

(2) DIF＞Δ 1+K1*IT1 _Rms﹠amp; IT1 _Rms＞Δ; Time-delay T1; Action policy: send out phase shift locking order to utmost point control system, stoppage in transit HVDC (High Voltage Direct Current) transmission system, the AC circuit breaker of tripping simultaneously, startup breaker fail protection;

(3) DIF＞Δ 2+K2*IT1 _RmsTime-delay T2; Action policy: send out phase shift locking order to utmost point control system, stoppage in transit HVDC (High Voltage Direct Current) transmission system, the AC circuit breaker of tripping simultaneously, startup breaker fail protection; Δ 2 is the three section protection definite value, and K2 is the 3rd section ratio brake coefficient, and T2 is the 3rd period operate time.

3. according to the described current conversion station DC filter of claim 2 differential protecting method, it is characterized in that the high-pressure side is determined every the arcing ability of cutter by primary equipment DC filter high-pressure side every cutter arcing ability set point Δ; Three section protection definite value Δ 2, the 3rd section ratio brake coefficient K2 and the 3rd section action delay T2 according to DC filter and high-pressure side the short circuit trouble point (F1) between cutter determine; First section and the second segment protect definite value Δ 1, first section and second section ratio brake coefficient K1 and first section and second section action delay T1 according to DC filter internal short circuit fault point and and the short circuit trouble point (F2, F3, F4) of low-pressure side between cutter determine.

4. current conversion station DC filter differential protecting method according to claim 1 is characterized in that, in the step 1), Wherein N is the sampling number in a power frequency period, and K is the setting coefficient,

Be the mean value of the interior IT1 of a power frequency period and IT4 difference.

5. current conversion station DC filter differential protecting method according to claim 4 is characterized in that, ${\mathrm{IT}1}_{\mathrm{rms}}=\frac{\sqrt{\underset{1}{\overset{N}{\mathrm{\Σ}}}{\mathrm{IT}1}^2}}{N}.$

6. current conversion station DC filter differential protection is characterized in that, comprising:

1) acquisition elements: gather DC filter high voltage side current signal IT1 and low-pressure side current signal IT4, and calculate electric current difference DIF according to the current signal of gathering;

2) judgment component: carry out differential protection and judge that criterion is DIF＞Δ+K*IT1 _Rms, Δ is the constant definite value, K is ratio brake coefficient, IT1 _RmsEffective value for high voltage side current;

3) executive component: when satisfying described criterion, the protection action.

7. current conversion station DC filter differential protection according to claim 6; it is characterized in that; the DC filter differential protection is divided into three sections, every section protection definite value, time-delay and action policy that has separately, and the criterion of three sections correspondences, time-delay and action policy are respectively:

(1) DIF＞Δ 1+K1*IT1 _Rms﹠amp; IT1 _Rms＜Δ; Time-delay T1; Action policy: draw back the DC filter high-pressure side every cutter; Δ is that the high-pressure side is every cutter arcing ability set point; Δ 1 is first section and the second segment protect definite value, and K1 is first section and second section ratio brake coefficient, and T1 is first section and second section action delay;

(2) DIF＞Δ 1+K1*IT1 _Rms﹠amp; IT1 _Rms＞Δ; Time-delay T1; Action policy: send out phase shift locking order to utmost point control system, stoppage in transit HVDC (High Voltage Direct Current) transmission system, the AC circuit breaker of tripping simultaneously, startup breaker fail protection;

(3) DIF＞Δ 2+K2*IT1 _RmsTime-delay T2; Action policy: send out phase shift locking order to utmost point control system, stoppage in transit HVDC (High Voltage Direct Current) transmission system, the AC circuit breaker of tripping simultaneously, startup breaker fail protection; Δ 2 is the three section protection definite value, and K2 is the 3rd section ratio brake coefficient, and T2 is the 3rd period operate time.

8. current conversion station DC filter differential protection according to claim 7 is characterized in that, the high-pressure side is determined every the arcing ability of cutter by primary equipment DC filter high-pressure side every cutter arcing ability set point Δ; Three section protection definite value Δ 2, the 3rd section ratio brake coefficient K2 and the 3rd section action delay T2 according to DC filter and high-pressure side the short circuit trouble point (F1) between cutter determine; First section and the second segment protect definite value Δ 1, first section and second section ratio brake coefficient K1 and first section and second section action delay T1 according to DC filter internal short circuit fault point and and the short circuit trouble point (F2, F3, F4) of low-pressure side between cutter determine.

9. current conversion station DC filter differential protection according to claim 6 is characterized in that, in the step 1),

Wherein N is the sampling number in a power frequency period, and K is the setting coefficient, Be the mean value of the interior IT1 of a power frequency period and IT4 difference.

10. current conversion station DC filter differential protection according to claim 9 is characterized in that, ${\mathrm{IT}1}_{\mathrm{rms}}=\frac{\sqrt{\underset{1}{\overset{N}{\mathrm{\Σ}}}{\mathrm{IT}1}^2}}{N}.$

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