CN104332971A

CN104332971A - Grid line wide-area backup protection method applicable to double-line tripping

Info

Publication number: CN104332971A
Application number: CN201410645038.4A
Authority: CN
Inventors: 曾惠敏
Original assignee: State Grid Corp of China SGCC; State Grid Fujian Electric Power Co Ltd; Maintenance Branch of State Grid Fujian Electric Power Co Ltd
Current assignee: State Grid Corp of China SGCC; State Grid Fujian Electric Power Co Ltd; Maintenance Branch of State Grid Fujian Electric Power Co Ltd
Priority date: 2014-11-12
Filing date: 2014-11-12
Publication date: 2015-02-04

Abstract

The invention discloses a grid line wide-area backup protection method applicable to double-line tripping. The grid line wide-area backup protection method adopts an existing wide-area measuring system of a power grid to synchronously measure voltage and current phasor of various transformer substations of the power grid to obtain synchronous data of the power grid; if the double lines of the power grid trip at the same time, the wide-area backup protection system computes an inverse matrix of a node admittance matrix of the power grid after a single line trips and computes the same after the double lines trip, and the calculated current of the lines and the measured line current by the existing wide-area measuring system constitute relay protection reference. By the grid line wide-area backup protection method, when the double lines of the power grid trip and the topological structure of the power grid changes, the current passing each line of the power grid can be directly calculated without rectifying the admittance matrix of the power grid after the double lines of the power grid trip at the same time, the integral calculation process can be completed within 200ms, and protection is fast in action.

Description

Power grid line wide area backup protection method suitable for double line tripping

Technical Field

The invention relates to the technical field of power system relay protection, in particular to a power grid line wide area backup protection method suitable for double line tripping.

Background

The task of relay protection is to reflect the fault and abnormal operation state of the protected element, and the relay protection can be divided into main protection and backup protection according to functions. The main protection is only responsible for quickly cutting off the fault of the protected element and is basically not influenced by the operation mode of the system. With the application of optical fiber channels, the main protection technology of high-voltage and ultrahigh-voltage systems based on double-end electrical quantity is becoming mature. The backup protection is also responsible for the remote backup protection of adjacent electrical elements, and the responsibility cannot be cancelled due to the possibility of failure of the direct-current power supply of the transformer substation. The existing power grid backup protection only reflects information of a protection installation position and is influenced by a power grid topological connection relation and an operation mode. In order to ensure the reliability, the configuration and setting have to be carried out according to the most severe condition; to ensure its selectivity, the rapidity and sensitivity of the backup protection have to be sacrificed. Meanwhile, as the structure of the power grid is increasingly complex, the following potential safety hazards are caused:

1) the backup protection has complex coordination relationship and long action time. The limit cutting time required by the stability of the power system may not be met in serious cases, and further the potential safety hazard of a large power grid is formed.

2) The difficulty of backup protection configuration and setting is high, the change of the operation mode of the power system cannot be tracked, and even the situation of protection mismatch or insufficient sensitivity may occur.

3) Backup protection cannot distinguish between internal faults and load flow diversion caused after fault removal, which may lead to a backup protection tripping in case of heavy load.

In a major power failure accident, although the backup protection of the power system acts correctly according to the design principle, the phenomenon that the system breakdown is objectively accelerated occurs. Therefore, research on a backup protection system considering the global information of the power grid is urgent.

In recent years, the advent of wide area synchronous measurement systems (WAMS) has made it possible to introduce system information in backup protection. The WAMS can synchronously acquire the electric phasor in the whole network, so that the dynamic process monitoring of the power system is realized; and secondly, the updating speed of the measurement is reduced from several seconds to dozens of milliseconds, so that conditions are created for realizing the dynamic process control of the power system, and the design of backup protection from the perspective of the overall optimum of the power grid becomes possible.

Disclosure of Invention

The invention aims to overcome the defects in the prior art and provides a power grid line wide-area backup protection method for realizing a power grid wide-area current protection function after double-line tripping by using the conventional power grid wide-area measurement system.

The purpose of the invention is realized by the following technical scheme:

the wide-area backup protection method for the power grid line adaptive to double-line tripping is characterized by comprising the following sequential steps of:

(1) the wide-area backup protection system realizes synchronous measurement of voltage and current phasors of each substation of the power grid by using the existing wide-area measurement system of the power grid, and acquires power grid synchronous data in real time; if the circuit breakers at the two ends of the circuit ij and the circuit lk are tripped off simultaneously, entering the step (2); the line ij is connected with the i transformer substation and the j transformer substation; the line lk is connected with the transformer substation I and the transformer substation k; 1, ·, n; j ═ 1.., n; 1,. n; k 1.., n; n is the total number of power grid substations; the line ij and the line lk are different lines;

(2) the wide area backup protection system calculates an inverse matrix of a grid node admittance matrix after the single line is tripped:

Y^-1-Y^-1M(M^TY^-1M-z_ij)^-1M^TY^-1

wherein z is_ijA line being line ijAn impedance; m [ 0.. 1.. 0. ] -1]^TThe matrix is an n multiplied by 1 dimensional matrix, the 1 st row and 1 st column element in the ith row in the M matrix is 1, the 1 st row and 1 st column element in the jth row in the M matrix is-1, and other elements are 0; 1, ·, n; j ═ 1.., n; n is the total number of power grid substations; y is a node admittance matrix of the power grid before the circuit breakers at the two ends of the circuit ij and the circuit lk are not tripped; y is^-1An inverse matrix of the node admittance matrix Y; (M)^TY^-1M-z_ij)^-1Is M^TY^-1M-z_ijThe inverse matrix of (1 x 1) -dimensional matrix; m^TA transposed matrix which is an M matrix;

(3) node admittance matrix Y of power grid after circuit breakers at two ends of circuit ij and circuit lk are simultaneously tripped and calculated by wide-area backup protection system_tInverse matrix Y of_t ^-1：

Y_t ^-1＝{Y^-1-Y^-1M(M^TY^-1M-z_ij)^-1M^TY^-1}{I-H(H^T(Y^-1-Y^-1M(M^TY^-1M-z_ij)^-1M^TY^-1)H-z_lk)^-1×H^T(Y^-1-Y^-1M(M^TY^-1M-z_ij)^-1M^TY^-1)}

Wherein z is_lkLine impedance of line lk; h ═ 0.. 1.. 0]^TThe matrix is an n multiplied by 1 dimensional matrix, the 1 st row and 1 st column element in the L matrix is 1, the 1 st row and 1 st column element in the k matrix is-1, and other elements are 0; 1,. n; k 1.., n; n is the total number of power grid substations; y is a node admittance matrix of the power grid before the circuit breakers at the two ends of the circuit ij and the circuit lk are not tripped; i is an n multiplied by n dimensional unit matrix, the diagonal elements of I are all 1, and the non-diagonal elements of I are all 0; h^TA transposed matrix which is an H matrix; (H)^T(Y^-1-Y^-1M(M^TY^-1M-z_ij)^-1M^TY^-1)H-z_lk)^-1Is H^T(Y^-1-Y^-1M(M^TY^-1M-z_ij)^-1M^TY^-1)H-z_lkThe inverse matrix of (1 x 1) -dimensional matrix; y is_tThe lower corner mark t has no practical physical significance, and the lower corner mark t is taken mainly to be distinguished from Y;

(4) the wide-area backup protection system calculates voltage phasor matrixes of all transformer substations of the power grid after circuit breakers at two ends of the circuit ij and the circuit lk are tripped simultaneously

Wherein,

is an n x 1 dimensional matrix and is,injecting current into nodes of substations numbered 1 st, 2 nd, 3 rd, 10 th, n-2 nd, n-1 th and n th after circuit breakers at two ends of the circuit ij and the circuit lk are tripped;

is an n x 1 dimensional matrix and is,the circuit breakers at two ends of the circuit ij and the circuit lk are numbered as voltage phasors of the transformer substations 1 st, 2 nd, 3 rd, n-2 nd, n-1 th and n th after being tripped;

(5) the wide-area backup protection system calculates the current flowing on the line pq after the circuit breakers at the two ends of the line ij and the line lk are tripped offAnd judgeIf the fault is not met, the wide area backup protection system judges that the line pq is a fault line, sends a tripping command to the circuit breakers at the two ends of the line pq and trips off the circuit breakers at the two ends of the line pq; wherein, p is 1. q ═ 1.., n; the line pq, the line ij and the line lk are different lines; n is power grid transformer substationTotal number; z is a radical of_pqIs the line impedance of line pq;measuring the current flowing on the line pq by the existing wide area measurement system after the circuit breakers at the two ends of the line ij and the line lk are tripped; the line pq is connected with the p transformer substation and the q transformer substation; i is_setTaking 0.3 times of the pq rated current of the line for setting a current threshold value;and the voltage phasors of the p transformer substation and the q transformer substation after the circuit breakers at the two ends of the circuit ij and the circuit lk are tripped off respectively.

Compared with the prior art, the invention has the following positive results:

the method comprises the steps of firstly, utilizing the existing wide area measurement system of the power grid to realize the synchronous measurement of voltage and current phasors of each transformer substation of the power grid, and acquiring power grid synchronous data; if the double lines of the power grid trip simultaneously, the wide area backup protection system calculates an inverse matrix of a power grid node admittance matrix after the single line trips, further calculates the inverse matrix of the power grid node admittance matrix after the double lines of the power grid trip simultaneously, then calculates voltage phasor matrices of all substations of the power grid after the double lines of the power grid trip simultaneously, calculates currents flowing through the lines after the double lines of the power grid trip simultaneously, and utilizes the calculated currents flowing through the lines and the current measured by the existing wide area measurement system to form a relay protection criterion. The method utilizes the existing wide area measurement system of the power grid to realize the wide area backup protection function of the power grid after the double lines of the power grid trip simultaneously. According to the method, when the dual lines of the power grid trip simultaneously and the topology structure of the power grid changes, the current flowing through each line of the power grid after the dual lines of the power grid trip simultaneously can be directly calculated without correcting the admittance matrix of the power grid, the whole calculation process can be completed within 200ms, the protection action speed is high and is faster than that of the existing line backup protection algorithm based on the local quantity decision, and a new defense line can be added between the dual lines of the power grid and the existing line backup protection algorithm on the premise of keeping the main protection function of the existing line and the line backup protection based on the local quantity decision.

Drawings

Fig. 1 is a general design scheme of wide-area current protection of a power grid line to which the invention is applied.

Detailed Description

The technical scheme of the invention is further detailed in the following according to the attached drawings of the specification.

Fig. 1 is a general design scheme of wide-area current protection of a power grid line to which the invention is applied. In fig. 1, the PMU is a synchrophasor measurement unit, the GPS is a time synchronization system, and 1, 2, 3, T-1, T, T +1, T +2, and n are numbers of substations in the power grid. The wide-area backup protection system utilizes the existing wide-area measurement system of the power grid to realize the synchronous measurement of the voltage and current phasors of each transformer substation of the power grid and acquire the synchronous data of the power grid in real time.

If the circuit breakers at the two ends of the circuit ij and the circuit lk are tripped simultaneously, the wide-area backup protection system calculates an inverse matrix of a grid node admittance matrix after the single circuit is tripped:

Y^-1-Y^-1M(M^TY^-1M-z_ij)^-1M^TY^-1

wherein z is_ijIs the line impedance of line ij; m [ 0.. 1.. 0. ] -1]^TThe matrix is an n multiplied by 1 dimensional matrix, the 1 st row and 1 st column element in the ith row in the M matrix is 1, the 1 st row and 1 st column element in the jth row in the M matrix is-1, and other elements are 0; 1, ·, n; j ═ 1.., n; n is the total number of power grid substations; y is a node admittance matrix of the power grid before the circuit breakers at the two ends of the circuit ij and the circuit lk are not tripped, and is an n multiplied by n dimensional matrix; y is^-1The inverse matrix of the node admittance matrix Y is an n multiplied by n dimensional matrix; (M)^TY^-1M-z_ij)^-1Is M^TY^-1M-z_ijThe inverse matrix of (1 x 1) -dimensional matrix; m^TA transposed matrix of the M matrix is a 1 Xn dimensional matrix; m^TY^-1M-z_ijIs a 1 x 1 dimensional matrix.

Grid node admittance matrix Y after wide-area backup protection system calculates that circuit breakers at two ends of circuit ij and circuit lk are tripped simultaneously_tInverse matrix Y of_t ^-1：

Wherein z is_lkLine impedance of line lk; h ═ 0.. 1.. 0]^TThe matrix is an n multiplied by 1 dimensional matrix, the 1 st row and 1 st column element in the L matrix is 1, the 1 st row and 1 st column element in the k matrix is-1, and other elements are 0; 1,. n; k 1.., n; n is the total number of power grid substations; y is a node admittance matrix, n multiplied by n dimensional matrix, of the power grid before the circuit breakers at the two ends of the line ij and the line lk are not tripped; i is an n multiplied by n dimensional unit matrix, the diagonal elements of I are all 1, and the off-diagonal elements of I are all 0; (H)^T(Y^-1-Y^-1M(M^TY^-1M-z_ij)^-1M^TY^-1)H-z_lk)^-1Is H^T(Y^-1-Y^-1M(M^TY^-1M-z_ij)^-1M^TY^-1)H-z_lkThe inverse matrix of (1 x 1) -dimensional matrix; h^TThe matrix is a transposed matrix of an H matrix and is a 1 multiplied by n dimensional matrix; y is_t、Y_t ^-1Are all n × n dimensional matrixes; h^T(Y^-1-Y^-1M(M^TY^-1M-z_ij)^-1M^TY^-1)H-z_lkIs a 1 x 1 dimensional matrix.

Wide area backup protectionThe protection system calculates voltage phasor matrix of each transformer substation of the power grid after circuit breakers at two ends of the circuit ij and the circuit lk are tripped simultaneously

Wherein,

is an n x 1 dimensional matrix and is,and the circuit breakers at the two ends of the circuit ij and the circuit lk are numbered as the voltage phasors of the transformer substations 1 st, 2 nd, 3 rd, n-2 nd, n-1 th and n th after being tripped.

The wide-area backup protection system calculates the current flowing on the line pq after the circuit breakers at the two ends of the line ij and the line lk are tripped offAnd judgeIf the fault is not met, the wide area backup protection system judges that the line pq is a fault line, sends a tripping command to the circuit breakers at the two ends of the line pq and trips off the circuit breakers at the two ends of the line pq; wherein, p is 1. q ═ 1.., n; the line pq, the line ij and the line lk are different lines; n is the total number of power grid substations; z is a radical of_pqIs the line impedance of line pq;the existing wide area measurement system measures the current flowing on the line pq after the circuit breakers at the two ends of the line ij and the line lk are tripped offThe current of (a); the line pq is connected with the p transformer substation and the q transformer substation; i is_setTaking 0.3 times of the pq rated current of the line for setting a current threshold value;and the voltage phasors of the p transformer substation and the q transformer substation after the circuit breakers at the two ends of the circuit ij and the circuit lk are tripped off respectively.

The method comprises the steps of firstly, utilizing the existing wide area measurement system of the power grid to realize the synchronous measurement of voltage and current phasors of each transformer substation of the power grid, and acquiring power grid synchronous data; if the double lines of the power grid trip simultaneously, the wide area backup protection system calculates an inverse matrix of a power grid node admittance matrix after the single line trips, further calculates the inverse matrix of the power grid node admittance matrix after the double lines of the power grid trip simultaneously, then calculates voltage phasor matrices of all substations of the power grid after the double lines of the power grid trip simultaneously, calculates currents flowing through the lines after the double lines of the power grid trip simultaneously, and utilizes the calculated currents flowing through the lines and the current measured by the existing wide area measurement system to form a relay protection criterion.

The invention realizes the power grid wide-area backup protection function after the double lines of the power grid trip simultaneously by utilizing the existing wide-area measurement system of the power grid. According to the method, when the dual lines of the power grid trip simultaneously and the topology structure of the power grid changes, the current flowing through each line of the power grid after the dual lines of the power grid trip simultaneously can be directly calculated without correcting the admittance matrix of the power grid, the whole calculation process can be completed within 200ms, the protection action speed is high and is faster than that of the existing line backup protection algorithm based on the local quantity decision, and a new defense line can be added between the dual lines of the power grid and the existing line backup protection algorithm on the premise of keeping the main protection function of the existing line and the line backup protection based on the local quantity decision.

The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention.

Claims

1. The wide-area backup protection method for the power grid line adaptive to double-line tripping is characterized by comprising the following sequential steps of:

(1) the wide-area backup protection system realizes synchronous measurement of voltage and current phasors of each substation of the power grid by using the existing wide-area measurement system of the power grid, and acquires power grid synchronous data in real time; if the circuit breakers at the two ends of the circuit ij and the circuit lk are tripped off simultaneously, entering the step (2); the line ij is connected with the i transformer substation and the j transformer substation; the line lk is connected with the transformer substation I and the transformer substation k; 1, ·, n; j ═ 1.., n; 1,. n; k 1.., n; n is the total number of power grid substations; the line ij and the line lk are different lines,

Y^-1-Y^-1M(M^TY^-1M-z_ij)^-1M^TY^-1

wherein z is_ijIs the line impedance of line ij; m [ 0.. 1.. 0. ] -1]^TThe matrix is an n multiplied by 1 dimensional matrix, the 1 st row and 1 st column element in the ith row in the M matrix is 1, the 1 st row and 1 st column element in the jth row in the M matrix is-1, and other elements are 0; 1, ·, n; j ═ 1.., n; n is the total number of power grid substations; y is a node admittance matrix of the power grid before the circuit breakers at the two ends of the circuit ij and the circuit lk are not tripped; y-1 is an inverse matrix of the node admittance matrix Y; (M)^TY^-1M-z_ij)^-1Is M^TY^-1M-z_ijThe inverse matrix of (1 x 1) -dimensional matrix; m^TIs a transposed matrix of the M matrix.

(3) Node admittance matrix Y of power grid after circuit breakers at two ends of circuit ij and circuit lk are simultaneously tripped and calculated by wide-area backup protection system_tInverse matrix of

Wherein z is_lkLine impedance of line lk; h ═ 0.. 1.. 0]^TThe matrix is an n multiplied by 1 dimensional matrix, the 1 st row and 1 st column element in the L matrix is 1, the 1 st row and 1 st column element in the k matrix is-1, and other elements are 0; 1,. n; k 1.., n; n is the total number of power grid substations; y is a node admittance matrix of the power grid before the circuit breakers at the two ends of the circuit ij and the circuit lk are not tripped; i is an n multiplied by n dimensional unit matrix, the diagonal elements of I are all 1, and the off-diagonal elements of I are all 0; h^TA transposed matrix which is an H matrix; (H)^T(Y^-1-Y^-1M(M^TY^-1M-z_ij)^-1M^TY^-1)H-z_lk)-¹Is H^T(Y^-1-Y^-1M(M^TY^-1M-z_ij)^-1M^TY^-1)H-z_lkThe inverse matrix of (1 x 1) -dimensional matrix;

\dot{U} = Y_{t}^{- 1} \dot{I};

Wherein,

\dot{I} = {[\begin{matrix} {\dot{I}}_{1} & {\dot{I}}_{2} & {\dot{I}}_{3} & . . . & {\dot{I}}_{n - 2} & {\dot{I}}_{n - 1} & {\dot{I}}_{n} \end{matrix}]}^{T}

is an n x 1 dimensional matrix and is,the circuit breakers at the two ends of the circuit ij and the circuit lk are numbered as 1 st, 2 nd, 3 rd, n-2 th, n-1 th and n th after being tripped offInjecting current into a node of the power station;

\dot{U} = {[\begin{matrix} {\dot{U}}_{1} & {\dot{U}}_{2} & {\dot{U}}_{3} & . . . & {\dot{U}}_{n - 2} & {\dot{U}}_{n - 1} & {\dot{U}}_{n} \end{matrix}]}^{T}

(5) the wide-area backup protection system calculates the current flowing on the line pq after the circuit breakers at the two ends of the line ij and the line lk are tripped offAnd judgeIf the fault is not met, the wide area backup protection system judges that the line pq is a fault line, sends a tripping command to the circuit breakers at the two ends of the line pq and trips off the circuit breakers at the two ends of the line pq; wherein, p is 1. q ═ 1.., n; the line pq, the line ij and the line lk are different lines; n is the total number of power grid substations; z is a radical of_pqIs the line impedance of line pq;measuring the current flowing on the line pq by the existing wide area measurement system after the circuit breakers at the two ends of the line ij and the line lk are tripped; the line pq is connected with the p transformer substation and the q transformer substation; i is_setTaking 0.3 times of the pq rated current of the line for setting a current threshold value;and the voltage phasors of the p transformer substation and the q transformer substation after the circuit breakers at the two ends of the circuit ij and the circuit lk are tripped off respectively.