CN-116106676-B - Short-circuit current direct-current component calculation method, system and equipment of power system

CN116106676BCN 116106676 BCN116106676 BCN 116106676BCN-116106676-B

Abstract

The application relates to a method, a system and equipment for calculating short-circuit current direct current components of an electric power system, wherein the method comprises the steps of obtaining fault nodes of a network topology structure of the electric power system, the number M of branches connected with the fault nodes, active voltage phasors of the fault points and branch current phasors of each branch connected with the fault nodes; the method comprises the steps of obtaining an equivalent impedance phasor and an attenuation time constant corresponding to each branch according to active voltage phasors and branch current phasors of a fault point, obtaining time after the fault, obtaining a short-circuit current direct-current component according to the time after the fault, the branch current phasors and the attenuation time constant, and obtaining the short-circuit current direct-current component of the fault node to the ground according to the short-circuit current direct-current component of M branches. According to the method, each branch is connected with the fault node, the short-circuit current direct-current component of the fault node is calculated independently, and the attenuation time constant of the branch is combined in the process of calculating the short-circuit current direct-current component of the branch, so that the result of calculating the short-circuit current direct-current component of the branch is more accurate.

Inventors

SU YINSHENG
MAO ZHENYU
XU GUANGHU
ZHAO LIGANG
YAO HAICHENG
TU SIJIA

Assignees

中国南方电网有限责任公司

Dates

Publication Date: 20260505
Application Date: 20221111

Claims (9)

1. The short-circuit current direct current component calculation method for the power system is applied to the power system with larger branch impedance than deviation, and is characterized by comprising the following steps of: Acquiring fault nodes of a network topology structure of an electric power system, the number M of branches connected with the fault nodes, active voltage phasors of the fault points and branch current phasors of each branch connected with the fault nodes; Calculating according to the active voltage phasors of the fault points and the branch current phasors of each branch, and obtaining an equivalent impedance phasor corresponding to each branch and a decay time constant of a short-circuit current direct-current component; Obtaining the time after the fault corresponding to the decay time constant, and obtaining the short-circuit current direct-current component of the corresponding branch according to the time after the fault, the branch current phasor of each branch and the decay time constant; The method for obtaining the attenuation time constant of the equivalent impedance phasors and the short-circuit current direct-current components corresponding to each branch comprises the following steps of: calculating by adopting an equivalent impedance phasor formula according to the active voltage phasor of the fault point and the branch current phasor of each branch to obtain an equivalent impedance phasor corresponding to each branch; Calculating by adopting an attenuation time calculation formula according to the equivalent impedance phasor of each branch, and obtaining an attenuation time constant of a short-circuit current direct-current component corresponding to the branch; wherein, the equivalent impedance phasor formula is: The decay time calculation formula is as follows: , Wherein Z equ,x is the equivalent impedance phasor of the xth branch, As the active voltage phasor at the point of failure, L equ,x and R equ,x are equivalent reactance and equivalent resistance of the xth branch respectively, T x is decay time constant of short-circuit current direct current component of the xth branch, To obtain the value of the real part in the equivalent impedance phasor Z equ,x , To obtain the value of the imaginary part in the equivalent impedance phasor Z equ,x .
2. The method of calculating a short-circuit current direct current component of an electric power system according to claim 1, wherein obtaining a branch current phasor for each branch connected to the fault node in a network topology of the electric power system comprises: Acquiring second parameter data of a network topology structure of an electric power system, wherein the second parameter data comprises a reference node, n common nodes, a system nominal voltage, a voltage coefficient, the self admittances of the n common nodes, a first branch admittance between every two common nodes and a second branch admittance between the fault node and the common nodes; determining fault node conditions corresponding to the fault nodes according to the total nominal voltage and the voltage coefficient, and constructing a node current balance equation according to the self admittances of n common nodes and all first branch admittances; performing primary equivalent transformation on the node current balance equation, and performing back-generation calculation by adopting the fault node condition to obtain node voltage phasors of each common node; And obtaining the branch current phasors of the branch connected with the fault node according to the active voltage phasors of the fault point, the node voltage phasors of the common node connected with the fault node and the second branch admittance calculation corresponding to the common node.
3. The method of calculating a short-circuit current direct current component of an electric power system according to claim 2, wherein determining a fault node condition corresponding to the fault node from the total nominal voltage and the voltage coefficient includes: Calculating by adopting an active voltage calculation formula according to the unified nominal voltage and the voltage coefficient to obtain an active voltage phasor of a fault point; Determining a fault node condition corresponding to the fault node according to the fault point active voltage phasors; the active voltage calculation formula is as follows: the fault node conditions are: In which, in the process, Active voltage phasors for points of failure C is the voltage coefficient, U is the nominal voltage of the system, Is the voltage phasor of the failed node.
4. The method for calculating the short-circuit current direct current component of the electric power system according to claim 2, wherein a node current balance equation is constructed according to the self admittances of the n common nodes and all the first branch admittances, the node current balance equation being: Wherein when i=j, Y ij is the self-admittance of the ith or jth normal node, when i+notej, Y ij is the first branch admittance between the ith normal node and the jth normal node, and Y ij =0 if no connection branch exists between the ith normal node and the jth normal node, Is the node voltage phasor of the nth common node.
5. The method for calculating the short-circuit current direct current component of the power system according to claim 1, wherein the short-circuit current direct current component of the corresponding branch is obtained by calculating a first calculation formula according to the time after failure, the branch current phasor of each branch and the decay time constant, and the first calculation formula is as follows: Calculating the short-circuit current direct-current components of the M branches by adopting a second calculation formula to obtain the short-circuit current direct-current components of the fault node to the ground, wherein the second calculation formula is as follows: Where t is the post-failure time corresponding to the decay time constant, Is the branch current phasor of the xth branch, For the short-circuit current direct current component of the xth branch, T x is the decay time constant of the short-circuit current direct current component of the xth branch, and I DC is the short-circuit current direct current component of the fault node to ground.
6. A short-circuit current direct-current component computing system of an electric power system is applied to the electric power system with branch impedance larger than deviation, and is characterized by comprising a data acquisition module, a first computing module and a second computing module; The data acquisition module is used for acquiring fault nodes of a network topological structure of the power system, the number M of branches connected with the fault nodes, active voltage phasors of the fault points and branch current phasors of each branch connected with the fault nodes; The first calculation module is used for calculating according to the active voltage phasors of the fault points and the branch current phasors of each branch, and obtaining an equivalent impedance phasor corresponding to each branch and an attenuation time constant of a short-circuit current direct current component; the second calculation module is used for obtaining the time after the fault corresponding to the decay time constant, calculating according to the time after the fault, the branch current phasors of each branch and the decay time constant, and obtaining the short-circuit current direct-current components of the corresponding branch; The method for obtaining the attenuation time constant of the equivalent impedance phasors and the short-circuit current direct-current components corresponding to each branch comprises the following steps of: calculating by adopting an equivalent impedance phasor formula according to the active voltage phasor of the fault point and the branch current phasor of each branch to obtain an equivalent impedance phasor corresponding to each branch; Calculating by adopting an attenuation time calculation formula according to the equivalent impedance phasor of each branch, and obtaining an attenuation time constant of a short-circuit current direct-current component corresponding to the branch; wherein, the equivalent impedance phasor formula is: The decay time calculation formula is as follows: , Wherein Z equ,x is the equivalent impedance phasor of the xth branch, As the active voltage phasor at the point of failure, L equ,x and R equ,x are equivalent reactance and equivalent resistance of the xth branch respectively, T x is decay time constant of short-circuit current direct current component of the xth branch, To obtain the value of the real part in the equivalent impedance phasor Z equ,x , To obtain the value of the imaginary part in the equivalent impedance phasor Z equ,x .
7. The system of claim 6, wherein the data acquisition module comprises a parameter acquisition sub-module, an equation construction sub-module, a third calculation sub-module, and a fourth calculation sub-module; The parameter acquisition sub-module is used for acquiring second parameter data of a network topology structure of the power system, wherein the second parameter data comprises a reference node, n common nodes, a system nominal voltage, a voltage coefficient, the self admittances of the n common nodes, a first branch admittance between every two common nodes and a second branch admittance between the fault node and the common nodes; The equation construction submodule is used for determining fault node conditions corresponding to the fault nodes according to the system nominal voltage and the voltage coefficient, and constructing node current balance equations according to the self admittances of n common nodes and all first branch admittances; The third calculation sub-module is used for performing primary equivalent transformation on the node current balance equation and performing back-generation calculation by adopting the fault node condition to obtain node voltage phasors of each common node; the fourth calculation sub-module is configured to obtain a branch current phasor of a branch connected to the fault node according to the active voltage phasor of the fault point, the node voltage phasor of the common node connected to the fault node, and the second branch admittance corresponding to the common node.
8. The system of claim 6, wherein the second calculation module is further configured to calculate, according to the post-fault time, the branch current phasors and the decay time constants of each branch, by using a first calculation formula to obtain a short-circuit current dc component of the corresponding branch, calculate, according to a second calculation formula, the short-circuit current dc components of M branches to obtain a short-circuit current dc component of the fault node to ground, where the first calculation formula is: The second calculation formula is as follows: Where t is the post-failure time corresponding to the decay time constant, Is the branch current phasor of the xth branch, For the short-circuit current direct current component of the xth branch, T x is the decay time constant of the short-circuit current direct current component of the xth branch, and I DC is the short-circuit current direct current component of the fault node to ground.
9. A terminal device comprising a processor and a memory; the memory is used for storing program codes and transmitting the program codes to the processor; the processor is configured to execute the short-circuit current direct current component calculation method of the electric power system according to any one of claims 1 to 5 according to instructions in the program code.

Description

Short-circuit current direct-current component calculation method, system and equipment of power system Technical Field The present application relates to the field of short-circuit current technologies of power systems, and in particular, to a method, a system, and an apparatus for calculating a dc component of a short-circuit current of a power system. Background The attenuation of the direct current component of the short circuit current is slowed down, the direct current component content of the short circuit impact current, the short circuit full current and the direct current component content of the breaker which needs to break the current are increased, the test on whether certain breakers with small breaking capacity margin in the power grid can timely break the short circuit current according to the configuration requirement is serious, and hidden hazards are buried for the safe operation of the power system. At present, attention to short-circuit current calculation is mainly focused on the calculation aspect of short-circuit current periodic components, due attention to direct-current components and attenuation thereof in short-circuit current is absent in practical engineering application, and a simple and practical method and tool for engineering are absent in the calculation of direct-current component attenuation. Therefore, it is needed to accurately calculate the short-circuit current direct current component by using electromagnetic transient simulation, and put forward a practical calculation algorithm of the short-circuit current direct current component. For a three-phase symmetrical circuit of a power grid supplied by an infinite power supply, assuming that a three-phase symmetrical short circuit occurs at the time t=0, the expression of the short-circuit current direct current component in the power system is as followsIn the formula (I), in the formula (II),For the voltage initial angle of the power grid,For the current period component amplitude during normal operation of the grid,Is the loop impedance angle during normal operation of the power grid,The forced component of the short-circuit current is generated by the action of the power supply electromotive force, has the same change rule as the power supply electromotive force, and the amplitude of the forced component is kept unchanged in the transient process, and is also called a periodic component because the forced component is periodically changed according to a sine rule; Is the amplitude of the short-circuit current periodic component; is the impedance angle of the short circuit loop; The free component of the short-circuit current is irrelevant to an external power supply, and the current in the inductance loop cannot be generated suddenly and decays to zero along with time, so that the current decays exponentially and is usually called a direct current component and an aperiodic component; the time constant of the short circuit loop is the ratio of the inductance L and the resistance R of the short circuit loop ) Its magnitude reflects how fast the free component decays. The expression of the short-circuit current direct current component in the power system shows that the initial value of the short-circuit current direct current component is related to the initial phase angle of the power supply voltage and the current value in the loop before short-circuit, and the decay time is related to the running mode and the grid structure when short-circuit occurs. The existing examination of short-circuit current data mainly focuses on calculating periodic components, but neglects the influences of direct current components and decay time constants, and does not make a quantitative analysis on the influence degree. In recent years, with the development of ultra-high voltage transmission engineering, in order to reduce transmission loss, the capacities of a generator and a transformer in the ultra-high voltage transmission engineering are gradually increased, the resistance of a transmission line is further reduced, the reactance resistance ratio of a short-circuit point equivalent power system is increased, the attenuation time constant of a direct-current component is increased, and the influence of the short-circuit current direct-current component on a power grid is increasingly prominent. Under the short-circuit fault, the attenuation speed of the direct-current component of the short-circuit current is slower and slower, and the influence on the actual breaking capacity of the circuit breaker is more and more obvious. Therefore, only the direct current component of the short circuit current attenuated with time on each circuit breaker branch connected with the short circuit node is accurately calculated, and an effective basis can be provided for checking the breaking capacity of the circuit breaker. The existing attenuation time constant calculation method commonly used for the short-circuit current direct-current com