CN-122026344-A - Single-phase grounding identification, loop closing operation and load transfer method and system under consideration of multiple faults of distributed power supply

CN122026344ACN 122026344 ACN122026344 ACN 122026344ACN-122026344-A

Abstract

The invention discloses a single-phase grounding identification, loop closing operation and load transfer method and system under the condition of multiple faults of a distributed power supply, comprising the following steps of eliminating the interference of resonance and high-voltage side fusing of a voltage transformer according to the voltage amplitude and real-time fluctuation condition under the condition of multiple faults of a power distribution system, and identifying whether the power distribution system is in a single-phase grounding fault state; the method comprises the steps of calculating balanced power flow after loop closing according to an equivalent circuit before loop closing operation of a power distribution system with single-phase earth faults, determining an earth fault current increment margin according to partial or total compensation line capacitive current of inductive current flowing through an arc suppression coil when the single-phase earth faults occur, calculating the sum of line currents after loop closing according to the balanced power flow and the earth fault current increment margin, calculating impulse current which can be generated at the moment of loop closing operation of the power distribution network, and if the sum of the line currents after loop closing does not exceed a line limit value and the effective value of the impulse current is smaller than a corresponding line quick-break protection fixed value, meeting loop closing conditions, allowing loop closing operation, and if the sum of the line currents after loop closing exceeds the line limit value or the effective value of the impulse current is not smaller than the corresponding line quick-break protection fixed value, not meeting the loop closing conditions, and adopting power failure operation under a distributed power source considered scene. The invention can accurately identify single-phase earth faults of the power distribution network, is used for mode adjustment and fault treatment of the power distribution network with single-phase earth faults, and can improve the accuracy of loop closing check under the condition of earth faults and the safety of power failure transfer under the participation of a distributed power supply.

Inventors

LI ZHUQING
LIU HONGXIA
SHAN YUECHEN
HUO JIAN
ZHOU CHUNSHENG
SHI DONGMING
SHAO MINGYAN
DONG XIN
Chen kuo
ZHANG RUIZHE
XU XIN

Assignees

国网山东省电力公司济南供电公司

Dates

Publication Date: 20260512
Application Date: 20251229

Claims (10)

1. A single-phase grounding identification, loop closing operation and load transfer method and system under multiple faults of a distributed power supply are considered, which are characterized by comprising the following steps: according to the voltage amplitude and the real-time fluctuation condition, eliminating the interference of resonance and high-voltage side fusing of a voltage transformer, and identifying whether the power distribution system is in a single-phase grounding fault state; calculating balanced power flow after loop closing according to an equivalent circuit before loop closing operation of the power distribution system with single-phase grounding faults; The power distribution system adopts a neutral point to be grounded through an arc suppression coil, and the increment margin of the grounding fault current is determined according to the capacitive current of a part or all compensation circuit of the inductive current flowing through the arc suppression coil when a single-phase grounding fault occurs; calculating the sum of the currents of all the circuits after loop closing according to the balanced power flow and the earth fault current increment margin; calculating impact current generated at the moment of closing the loop when the power distribution network is operated to close the loop; If the sum of the circuit currents after closing the ring does not exceed the circuit current limit value and the effective value of the impact current is smaller than the corresponding circuit quick-break protection fixed value, the ring closing condition is met, and the ring closing operation is allowed; If the sum of the circuit currents after the loop closing exceeds the circuit current limit value or the effective value of the impact current is not smaller than the corresponding circuit quick-break protection fixed value, the loop closing condition is not met, and the power failure operation under the distributed power supply scene is considered.
2. The method for single-phase earth fault identification, loop closing operation and load transfer under multiple faults considered of a distributed power supply according to claim 1, characterized in that if the two-phase voltage of the bus of the power distribution system does not exceed the line voltage and is not approximately equal to the phase voltage, then the single-phase earth fault is judged.
3. The method for single-phase ground identification, loop closing operation and load transfer under multiple faults considering distributed power supply according to claim 1, wherein the ground fault current increment margin is less than or equal to 10A.
4. The method for single-phase earth identification, loop closing operation and load transfer under multiple faults considering distributed power supply according to claim 1, wherein if the loop closing condition is not satisfied, the loop closing operation is not allowed.
5. The method for single-phase earth identification, loop closing operation and load transfer under multiple faults considering distributed power supplies according to claim 4, wherein when the loop closing operation is not allowed, loop closing operation check is carried out again by adjusting the voltage or load of the relevant lines of the power distribution network.
6. The method for single-phase grounding identification, loop closing operation and load transfer under multiple faults considering distributed power supplies according to claim 1, wherein the voltage difference between two ends of a switch before loop closing is used as an equivalent power supply of a Thevenin equivalent circuit, the Thevenin equivalent impedance after loop closing of a circuit is calculated, and the balanced load flow after loop closing is calculated according to the equivalent power supply and the Thevenin equivalent impedance.
7. The method for single-phase grounding identification, loop closing operation and load transfer under multiple faults considering distributed power supplies according to claim 6, wherein voltages at two ends of a switch before loop closing are obtained specifically through a power distribution automation SCADA system, a power distribution automation system telemetry device or through a power flow calculation result before loop closing operation.
8. The method of claim 6, wherein the equivalent impedance of the integrated ring is the sum of the equivalent impedances of the respective lines and the corresponding transformers in the entire integrated ring circuit.
9. The method for single-phase grounding identification, loop closing operation and load transfer under multiple failures of distributed power supply according to claim 1, the voltage after closing the loop is regarded as 0.
10. A single phase earth identification, loop closing operation and load transfer system under multiple faults considering distributed power, comprising: The multiple fault identification module is used for eliminating resonance and interference of fusing of the high-voltage side of the voltage transformer under multiple faults and identifying whether the power distribution system is in a single-phase grounding fault state or not; the balanced power flow calculation module is used for calculating balanced power flow after loop closing according to an equivalent circuit before loop closing operation of the power distribution system with single-phase grounding faults; The current increment margin determining module is used for determining the grounding fault current increment margin according to the capacitive current of a part or all of compensation lines of the inductive current flowing through the arc suppression coil when the single-phase grounding fault occurs when the power distribution system adopts the neutral point to be grounded through the arc suppression coil; The loop closing current calculation module is used for calculating the sum of all the line currents after loop closing according to the balanced power flow and the earth fault current increment margin; the loop closing impact current calculation module is used for calculating impact current generated at the moment of loop closing when the power distribution network performs loop closing operation; the loop closing judging module is used for meeting the loop closing condition and allowing loop closing operation if the sum of the circuit currents after loop closing does not exceed the circuit current limit value and the effective value of the impact current is smaller than the corresponding circuit quick-break protection fixed value; And the power failure load transfer module is used for considering the distributed power supply to safely transfer the load under the condition of considering the power failure of the distributed power supply access if the loop closing condition is not met.

Description

Single-phase grounding identification, loop closing operation and load transfer method and system under consideration of multiple faults of distributed power supply Technical Field The invention relates to the field of power distribution network maintenance, in particular to a single-phase grounding identification, loop closing operation and load transfer method and system under multiple faults of a distributed power supply. Background Distribution systems typically employ closed loop wiring and open loop operation. The ring-closing power regulation operation is not only an important guarantee for improving the power supply reliability, but also an important means for regulating and controlling personnel during fault treatment of a power distribution system. The current 10kV power distribution system mostly adopts a neutral point indirect grounding mode, namely the neutral point is not grounded or is grounded through an arc suppression coil, under the grounding mode, the system can continuously run without cutting off a fault line when single-phase grounding faults occur, and the power supply reliability is improved. In a power distribution system, single-phase ground faults are one of faults with highest occurrence frequency, when a regulation person processes the single-phase ground faults, the regulation person needs to adopt loop closing and power regulating operation according to the operation mode of the power distribution system, a grounding bus is split or uninterrupted branch line load switching is carried out aiming at a grounding fault line, the fault range is reduced while reliable power supply is ensured, so that the fault line and a section are rapidly determined, and normal operation of a non-fault part is recovered. However, in a power distribution system with a neutral point indirectly grounded, zero sequence voltage rise and phase voltage abnormality can be caused by wire breakage, high-voltage fuse blowing of a voltage transformer and ferromagnetic resonance, so that a single-phase grounding signal is mistakenly sent out by the power distribution system, and the discrimination and identification of single-phase grounding faults are difficult. And for the distribution network running under the single-phase earth fault, the loop closing current and the single-phase earth fault current can influence the stability of the system and the safety of loop closing operation. If the loop closing current is too large, the overload of related equipment and even the brake drop of protection actions can be caused, and under the condition of single-phase grounding fault, unbalanced current appears in the distribution line, so that the risk of loop closing and power regulating operation is increased. Particularly, in a special operation mode, such as a case that a distribution line is transferred to a bus through a tie switch and is output, a single-phase grounding fault occurs, and the ground bus is divided by transferring power through a plurality of tie switches of different distribution lines, so that the operation mode and the change of related electric quantity are more complicated. The safety of the corresponding loop closing and power regulating operation cannot be confirmed by regulation personnel during fault treatment, and correct treatment cannot be timely and rapidly performed. In addition, if the traditional power failure transfer mode is adopted under the single-phase earth fault, the access of the distributed power supply also presents challenges for the safety of operation, and a dispatcher needs to support a new method system to properly handle the transfer operation under the single-phase earth fault. According to the superposition principle, the power flow after loop closing of the distribution line consists of the original power flow of each line before loop closing and the balanced power flow caused by the voltage difference between two ends of the loop closing switch. The original power flow of each line before loop closing is determined by line load, and the balanced power flow caused by loop closing operation can be calculated by the Thevenin equivalent principle: DeltaU and Respectively is the voltage difference of two sides of the ring closing pointReal and imaginary parts of (a) are provided. Balancing tideCan be expressed as: Because the reactance of the circuit and the transformer is relatively large and the resistance is relatively small in the power distribution system, the above formula can be simplified as: China patent 201210257852X proposes a power distribution network loop closing operation control method based on measurement and verification of voltage values and phase angle differences at two sides of a loop closing point, and whether the power distribution network meets loop closing conditions is verified through verification of voltage amplitude values, phase angles and variation amounts of the voltage values and the phase angles at two sides of the loop closing po