CN-121983927-A - Single-phase grounding protection method, system, equipment and medium for closed-loop distribution line

CN121983927ACN 121983927 ACN121983927 ACN 121983927ACN-121983927-A

Abstract

The invention discloses a single-phase grounding protection method, a system, equipment and a medium for a closed-loop power distribution line, belonging to the technical field of operation and maintenance of power systems, comprising the steps of collecting zero-sequence voltage and zero-sequence current and judging whether line faults exist or not; the method comprises the steps of detecting the existence of a line fault, collecting three-phase voltage data and three-phase current data in a first time window, extracting a zero-sequence voltage transient component and a zero-sequence current transient component, calculating a zero-sequence voltage phasor and a zero-sequence current phasor through frequency domain transformation, determining a phase difference between the zero-sequence voltage and the zero-sequence current, judging a fault direction, and controlling to send a control signal to an opposite-end protection device according to the fault direction. The invention can quickly and accurately identify the fault direction on the premise of not depending on the power frequency steady-state quantity, and can realize the accurate positioning and isolation of the fault section through the double-end cooperative mechanism, thereby solving the problems of low sensitivity and poor selectivity of single-phase grounding protection under the network structure.

Inventors

LI XINHAO
LIU TONG
WANG ZHUOYUE
SHI TONG
LIU PENGZHU
CAI YONGXIANG
XU YUTAO
FAN KE
LI QIANMIN
ZHANG HENGRONG
ZHANG SIYUAN
XIAO XIAOBING
YOU XINYU
WENG DI
ZHENG YOUZHUO
HE XIAOMENG
HE PENG
DU WEI
WANG FENG
HUANG WEI
LIU JIAHONG
WANG LIN
SUN JIAN
KE QINGPAI
Qiu Yangxin
LIN ZHIYUAN
SONG ZIHONG
YANG JIANBO
ZHOU MIAOMIAO
HE XINYI
SHI XUNTAO
MIAO YU
LIU ANJIANG
LI YUE
HAO SHUQING
ZHANG SONG

Assignees

贵州电网有限责任公司
南方电网科学研究院有限责任公司

Dates

Publication Date: 20260505
Application Date: 20251225

Claims (10)

1. A single-phase grounding protection method for a closed-loop power distribution line is characterized by comprising the following steps of, Collecting zero-sequence voltage and zero-sequence current, and carrying out fault detection according to the zero-sequence voltage and the zero-sequence current to judge whether line faults exist or not; three-phase voltage data and three-phase current data are collected in a first time window after line faults are detected, and zero-sequence voltage transient components and zero-sequence current transient components are extracted from the three-phase voltage data and the three-phase current data; Calculating a zero-sequence voltage phasor and a zero-sequence current phasor through frequency domain transformation according to the zero-sequence voltage transient component and the zero-sequence current transient component; Determining a phase difference between the zero-sequence voltage and the zero-sequence current according to the zero-sequence voltage phasors and the zero-sequence current phasors, and judging a fault direction according to the phase difference between the zero-sequence voltage and the zero-sequence current; And sending a control signal to the opposite-end protection device according to the fault direction control.
2. The method for single-phase grounding protection of a closed loop power distribution line according to claim 1, wherein the steps of collecting the detected zero sequence voltage and zero sequence current, and performing fault detection based on the detected zero sequence voltage and the detected zero sequence current, and judging whether a line fault exists comprise: Collecting and detecting zero sequence voltage and zero sequence current in real time at a bus of a transformer substation; Setting a zero sequence voltage threshold value and a zero sequence current threshold value, comparing the detected zero sequence voltage with the zero sequence voltage threshold value, and comparing the detected zero sequence current with the zero sequence current threshold value; if the detected zero sequence voltage is greater than the zero sequence voltage threshold value and the detected zero sequence current is greater than the zero sequence current threshold value, judging that a line fault exists; and if the detected zero sequence voltage is less than or equal to the zero sequence voltage threshold value or the detected zero sequence current is less than or equal to the zero sequence current threshold value, judging that no line fault exists.
3. The method for single-phase grounding protection of a closed loop power distribution line according to claim 2, wherein the step of collecting three-phase voltage data and three-phase current data within a first time window after detecting the presence of a line fault, and extracting zero-sequence voltage transient components and zero-sequence current transient components from the three-phase voltage data and the three-phase current data comprises: After detecting that a line fault exists, starting a time window with a preset length to cover an initial transient process after the fault; Collecting three-phase voltage data and three-phase current data in a time window; calculating accurate zero sequence voltage and accurate zero sequence current according to the three-phase voltage data and the three-phase current data; extracting voltage transient components and current transient components in the accurate zero sequence voltage and the accurate zero sequence current through a Butterworth band-pass filter; the voltage transient component and the current transient component are preprocessed.
4. A method of single-phase earth protection for a closed loop power distribution line according to claim 3, wherein the step of calculating the zero sequence voltage phasors and the zero sequence current phasors from the zero sequence voltage transient and the zero sequence current transient by frequency domain transformation comprises: frequency domain transformation is respectively carried out on the voltage transient component and the current transient component, so as to obtain a voltage amplitude-frequency characteristic curve and a current amplitude-frequency characteristic curve; determining transient dominant frequency according to the voltage amplitude-frequency characteristic curve; And extracting the zero-sequence voltage phasors and the zero-sequence current phasors by using frequency domain transformation according to the transient dominant frequency.
5. The method for single-phase earth protection of a closed loop power distribution line according to claim 4, wherein the step of determining a phase difference between the zero sequence voltage and the zero sequence current based on the zero sequence voltage phasor and the zero sequence current phasor, and determining the fault direction based on the phase difference between the zero sequence voltage and the zero sequence current comprises: Determining and extracting a zero-sequence voltage phase angle and a zero-sequence current phase angle according to the zero-sequence voltage phasors and the zero-sequence current phasors; calculating the phase difference between the zero sequence voltage and the zero sequence current according to the zero sequence voltage phase angle and the zero sequence current phase angle; And setting a preset action interval, and judging the fault direction according to whether the phase difference between the zero sequence voltage and the zero sequence current falls in the preset action interval.
6. The method for single-phase grounding protection of a closed loop power distribution line according to claim 5, wherein the step of determining the fault direction based on whether the phase difference between the zero sequence voltage and the zero sequence current is within a preset action interval comprises: if the phase difference between the zero sequence voltage and the zero sequence current is in the preset action interval, judging that the fault direction is a forward fault; And if the phase difference between the zero sequence voltage and the zero sequence current is outside the preset action interval, judging that the fault direction is reverse fault.
7. The method for single-phase ground protection for a closed-loop power distribution line according to claim 6, wherein the step of transmitting the control signal to the opposite-end protection device according to the fault direction control comprises: The method comprises the steps that a local side protection device monitors a communication channel from an opposite side protection device and receives an allowable tripping signal sent by an opposite side; When the protection device on the side judges that the fault direction is a forward fault, an allowable tripping signal is immediately generated, and the allowable tripping signal is sent to the protection device on the opposite end of the line through a communication channel; when the present side protection device judges that the fault direction is reverse fault, the present side protection device does not generate a tripping permission signal and does not send any tripping permission information to the opposite side protection device.
8. A single-phase grounding protection system for a ring distribution line, applying a single-phase grounding protection method for a ring distribution line according to any one of claims 1 to 7, comprising: the data acquisition module acquires zero-sequence voltage and zero-sequence current, and performs fault detection according to the zero-sequence voltage and the zero-sequence current to judge whether line faults exist or not; The transient component extraction module is used for acquiring three-phase voltage data and three-phase current data in a first time window after detecting that a line fault exists and extracting a zero-sequence voltage transient component and a zero-sequence current transient component from the three-phase voltage data and the three-phase current data; the zero-sequence phasor calculation module is used for calculating zero-sequence voltage phasors and zero-sequence current phasors through frequency domain transformation according to the zero-sequence voltage transient components and the zero-sequence current transient components; The fault direction judging module is used for determining the phase difference between the zero-sequence voltage and the zero-sequence current according to the zero-sequence voltage phasors and the zero-sequence current phasors and judging the fault direction according to the phase difference between the zero-sequence voltage and the zero-sequence current; and the signal control module is used for controlling and sending a control signal to the opposite-end protection device according to the fault direction.
9. A computer device comprising a memory and a processor, the memory storing a computer program, characterized in that the processor, when executing the computer program, implements the steps of a closed loop power distribution line single phase ground protection method as claimed in any one of claims 1 to 7.
10. A computer readable storage medium having stored thereon a computer program, wherein the computer program when executed by a processor implements the steps of a combined ring power distribution line single phase ground protection method of any of claims 1 to 7.

Description

Single-phase grounding protection method, system, equipment and medium for closed-loop distribution line Technical Field The invention relates to the technical field of operation and maintenance of power systems, in particular to a method, a system, equipment and a medium for protecting a single-phase grounding of a closed-loop power distribution line. Background With the large-scale access of distributed power sources such as photovoltaic power, wind power and energy storage in a power distribution network, the power supply structure of the power distribution network is gradually evolving from a traditional radial unidirectional power supply to a gridding, annular or partial annular operation mode. The distribution and controllability of the distributed power supply enable the power flow direction to be more flexible, the variation range of the branch current and voltage waveforms is obviously increased, and the line impedance asymmetry and the short-circuit capacity distribution become more complex. In order to improve the power supply quality, improve the reliability and enhance the robustness to faults, future power distribution networks aim at running a certain degree of feeder network gridding, annular connection and even micro-networks (microgrid), and dynamic power flow distribution and quick reconstruction are realized through multi-source interconnection, flexible active power distribution and authorized controllable switching elements. While many existing distribution lines are ring-wired topologies, they are open-loop in operation, i.e., a radial network, existing ground protection is primarily directed to radial networks, lacking effective protection for meshed or ring-connected operational lines. The neutral point of the power transmission network is directly grounded, the single-phase grounding fault current is large, the neutral point of the power distribution network is mainly in an arc suppression coil or ungrounded mode, and the zero sequence current is small during fault, so that the power distribution network grounding protection cannot adopt the same protection method as the power transmission network. The low-current grounding protection of the distribution line is generally protection logic based on radial assumption, and a protection algorithm is based on a single-path and single-end short circuit model, so that multipath shunt and complex power flow distribution during gridding or annular operation are difficult to deal with. The protection fixed value, time characteristic and selectivity also need to be dynamically adjusted under the grid chemical condition, and the traditional fixed value thinking line is easy to cause misoperation or refusal operation. In the gridding operation, the impedance and the short-circuit capacity of each branch circuit greatly fluctuate along with the tide distribution and the running state of the distributed power supply, so that a protection area and an action time sequence are unstable. The common grounding protection area division method is sensitive to online parameter changes and is easy to generate protection range drift. In a system with a neutral point which is not grounded or is grounded through compensation, single-phase grounding fault current is small, the direction protection sensitivity based on the power frequency zero sequence component is low, and a fault line is difficult to reliably identify. The research shows that the single-phase earth fault instantaneously excites a transient process, the amplitude of the high-frequency component of the zero-sequence voltage and the current in the transient process is large, the directional characteristic is obvious, and the transient process is not influenced by the power frequency compensation of the arc suppression coil, so that the transient protection method is little influenced by the neutral point compensation degree and the fault characteristic, acts rapidly, and the secondary fault caused by overvoltage due to the fault can be avoided. The existing transient protection is mainly aimed at a radiation network, the protection scheme in a mesh network is complex, and a transient protection method suitable for a non-grounding or arc suppression coil grounding network-shaped power distribution network needs to be developed. Disclosure of Invention The present invention has been made in view of the above-described problems. The invention solves the technical problems that in a closed loop distribution circuit with a neutral point not grounded or grounded through an arc suppression coil, single-phase grounding fault current is weak, the traditional direction protection sensitivity based on a power frequency zero sequence component is low, the fault direction is difficult to judge reliably, the traditional transient protection method is multi-faced to a radial network, the method cannot adapt to the selectivity problem caused by multi-power supply and multi-path current distribution in a net-sha