CN102856890A - Adaptive current differential protection method applied to high-compensation-degree series compensation system - Google Patents

Abstract

The invention provides an adaptive current differential protection method applied to a high-compensation-degree series compensation system. The method includes: a protection starting element acts when a series compensation line fails; judging whether current is in phase reversal or not; if not, using a first current differential protection algorithm for recognition of internal and external faults; if yes, using a second current differential protection algorithm for recognition of internal and external faults; and obtaining protection action characteristics in different states according to different differential protection algorithms. Using the adaptive current differential protection method can improve sensitivity of current differential protection in current reversal of internal faults of the high-compensation-degree series compensation system, prevent differential protection refused actions, and improve safety and reliability in system operation.

Description

A kind ofly be applicable to high compensativity string complement system self-adaptive current differential protecting method

Technical field

The invention belongs to the transmission line field, specifically relate to a kind of high compensativity string complement system (" high compensativity " refer to compensativity mend transmission system greater than 50% string) reverse differential protecting method of electric current that is applicable to.

Background technology

Modern transmission system adopts the mode that installs series compensation capacitance additional to realize in order to improve its transmission capacity and steady state stability limit usually.The transmission system that installs additional behind the series compensation capacitance is called the string complement system.The ratio of series compensation capacitance capacitor value and total track length resistance value is called the compensativity of circuit.Along with the enhancing of system, equivalent system impedance value to serial supplementary line two ends bus also reduces gradually.When serial compensation capacitance capacitor value during greater than the equivalent system impedance value of institute installation side bus, mending the egress line trackside at string occurs single-phase during through high resistance earthing fault, the reverse phenomenon of electric current can occur, namely flow to the leading system equivalent electrical source voltage of electric current (should be equivalent electromotive force after the current hysteresis without the string added time) of fault point from bus.This fault signature has a strong impact on the performance of differential current protection, tripping in the time of can causing differential current protection zone internal fault in the serious situation.Content of the present invention namely is the solution that proposes for this practical problem.

Summary of the invention

For improving the sensitivity of differential current protection action when serial supplementary line troubles inside the sample space electric current is reverse, the invention provides a kind of reverse self adaptation differential protecting method of serial supplementary line electric current that is applicable to.By the method can the Effective Raise serial supplementary line sensitivity of differential current protection when high resistance ground causes that electric current is reverse, prevent that the tripping of protection component from doing.

For achieving the above object, the invention provides a kind of high compensativity string complement system self-adaptive current differential protecting method that is applicable to, it is characterized in that described differential current protection method may further comprise the steps:

(1). serial supplementary line breaks down, then protection starting element action;

(2). judge whether the electric current in the serial supplementary line is anti-phase;

(3) if. be judged to be that electric current does not occur is reverse, then in the current differential protection algorithm, utilize following formula to carry out internal fault external fault and identify;

$|{\stackrel{\·}{I}}_M+{\stackrel{\·}{I}}_N|>k|{\stackrel{\·}{I}}_M-{\stackrel{\·}{I}}_N|$ (wherein the k value is taken as 0.6)

Described electric current

Steady-state value for circuit both sides phase current.The k value is ratio brake coefficient.

(4) if. be judged to be that electric current has occured is reverse, then in the current differential protection algorithm, utilize following formula to carry out internal fault external fault and identify;

$|{\stackrel{\·}{I}}_M+{\stackrel{\·}{I}}_N|>k\left(\right|{\stackrel{\·}{I}}_M|+|{\stackrel{\·}{I}}_N\left|\right)$ Wherein the k value is taken as

)

Described electric current

Steady-state value for circuit both sides phase current.The k value is ratio brake coefficient.

(5). draw string complement system current differential protection operating characteristics in electric current positive or anti-phase two kinds of situations according to current differential protection algorithms different in step (3), (4).

The invention provides in the technical scheme, in described step 3, utilize formula

(wherein the k value is taken as 0.6) is as the protection operating criterion.

The invention provides in the technical scheme, in described step 4, utilize formula

(wherein the k value is taken as 1/3) is as the protection operating criterion.

In the selecting technology scheme provided by the invention, described electric current is the steady-state value of circuit both sides phase current.

Compared with the prior art; a kind of high compensativity string complement system electric current current differential protection method when reverse that is applicable to provided by the invention; can improve the protection action sensitivity of troubles inside the sample space electric current when reverse, prevent the tripping of differential protection, bring favorable influence to relay protection of transmission line.

Description of drawings

Fig. 1 is high compensativity string complement system serial supplementary line fault schematic diagram;

Fig. 2 is the reverse self adaptation differential protection of serial supplementary line electric current calculation process.

Embodiment

The below is described in further details technical scheme of the present invention according to Figure of description.

Be illustrated in figure 1 as high compensativity string complement system serial supplementary line fault schematic diagram.

Be illustrated as the two ends power-supply system, E1 and E2 are respectively sending end and receiving end power supply; M, N are respectively two side bus; Serial compensation capacitance C is installed on the outlet of M side bus, and compensativity (ratio of serial compensation capacitance and line inductance) is greater than 50%; The fault point string mend and to side bus between; M side protection electric current is for to flow to circuit by bus M, and N side protection electric current is for to flow to circuit by bus N.

Be illustrated in figure 2 as the reverse self adaptation differential protection of serial supplementary line electric current calculation process, a kind ofly be applicable to high compensativity string complement system self-adaptive current differential protecting method, may further comprise the steps:

(1). serial supplementary line breaks down, then protection starting element action;

(2). utilize the reverse method of discrimination of electric current to carry out the reverse differentiation of electric current;

(3) if. be judged to be that electric current does not occur is reverse, then utilize formula in the current differential protection algorithm

(wherein the k value is taken as 0.6) carries out internal fault external fault identification as the protection operating criterion; This criterion does not occur for troubles inside the sample space higher sensitivity is arranged in the reverse situation of electric current at electric current.

(4) if. be judged to be that electric current has occured is reverse, then utilize formula in the current differential protection algorithm

(wherein the k value is taken as 1/3) carries out internal fault external fault identification as the protection operating criterion; This criterion has higher sensitivity for troubles inside the sample space in the reverse situation of electric current generation electric current.

(5). draw the protection operating characteristics according to different computational methods.

Be optimized for the differential algorithm under the different situations with 4 by step 3, can improve high compensativity system generation electric current oppositely after, the sensitivity of differential protection.

After the serial supplementary line fault, the action of protection starting element.Utilize the protection of this side to gather electric parameters whether the reverse differentiation of electric current occurs.According to differentiating the result, the protection installation place that utilization collects and the electric current of protected circuit offside With

Carry out different differential protection property calculation and comparison, obtain differential differentiation result.

What need statement is that content of the present invention and embodiment are intended to prove the practical application of technical scheme provided by the present invention, should not be construed as the restriction to protection range of the present invention.Those skilled in the art can do various modifications, be equal to and replace or improve inspired by the spirit and principles of the present invention.But these changes or modification are all in the protection range that application is awaited the reply.

Claims (2)

1. one kind is applicable to high compensativity string complement system self-adaptive current differential protecting method, it is characterized in that described differential current protection method may further comprise the steps:

(1). serial supplementary line breaks down, then protection starting element action;

(2). judge whether the electric current in the serial supplementary line is reverse;

(3) if. be judged to be that electric current does not occur is reverse, then in the current differential protection algorithm, utilize following formula to carry out internal fault external fault and identify;

$|{\stackrel{\·}{I}}_M+{\stackrel{\·}{I}}_N|>k|{\stackrel{\·}{I}}_M-{\stackrel{\·}{I}}_N|,$ Wherein in this formula, the k value is taken as 0.6;

Described electric current Be the steady-state value of circuit both sides phase current, the k value is ratio brake coefficient;

(4) if. be judged to be that electric current has occured is reverse, then in the current differential protection algorithm, utilize following formula to carry out internal fault external fault and identify;

$|{\stackrel{\·}{I}}_M+{\stackrel{\·}{I}}_N|>k\left(\right|{\stackrel{\·}{I}}_M|+|{\stackrel{\·}{I}}_N\left|\right),$ Wherein in this formula, the k value is taken as

Described electric current

Be the steady-state value of circuit both sides phase current, the k value is ratio brake coefficient;

(5). draw the string complement system in electric current current differential protection operating characteristics in two kinds of situations forward or backwards according to current differential protection algorithms different in step (3), (4).

2. self-adaptive current differential protecting method according to claim 1 is characterized in that, described electric current is the steady-state value of circuit both sides phase current.

Images