Method of differential protection in the power distribution networks based on phase difference principles

Patent metadata

Field	Value
Publication number	US-10082816-B2
Application number	US-201615076638-A
Country	US
Kind code	B2
Filing date	Mar 21, 2016
Priority date	Aug 7, 2015
Publication date	Sep 25, 2018
Grant date	Sep 25, 2018

Abstract

The invention relates to a method of differential protection in the power distribution networks based on phase difference principles. The method comprises the following steps: collecting the current and voltage signals of each loading switch; calculating phase difference between the corresponding currents at two adjacent loading switches, wherein at least one of the two adjacent loading switches accords with ΔI ϕ max >n·ΔI T +ΔI dz ; tripping the two adjacent loading switches if the phase difference corresponding to the two adjacent loading switches being greater than a threshold then a section between the two adjacent loading switches being determined as a fault section. The method only needs to calculate the phase difference between the corresponding currents at the two adjacent loading switches, and achieves the fault determination according to the phase difference being greater than the threshold. The method has low data synchronizing requirements, and processes the fault determination according to the collected signals. The time required for the entirely determining process is short, and a fast protecting response is achieved, thus the problem of slowly protecting response in the existing relay-protection method for the power distribution networks is solved.

First claim

What is claimed is:

1. A method of differential protection in the power distribution networks based on phase difference principles, wherein the method comprising the following steps:
1) collecting, via each intelligent feeder terminal unit in association with each loading switches, current and voltage signals of the each loading switch;
2) converting, via each analog/digital conversion plug of the each intelligent feeder terminal unit, the collected current and voltage signals to optical digital signals;
3) transmitting, via Ethernet, the optical digital signals to a differential protection control system;
4) calculating, via a protection logic module of the differential protection control system, phase difference between the corresponding currents at each two adjacent loading switches, wherein at least one of the two adjacent loading switches accords with ΔI ϕ max >n·ΔI T +ΔI dz ; ΔI ϕ max is the maximum value among the 3 phase current mutation values of a corresponding loading switch, n is a set proportional value, ΔI dz is a start value of phase current mutation, ΔI T is a threshold value;
5) determining, via the differential protection control system, the phase difference corresponding to two adjacent loading switches being greater than a threshold;
6) determining a section only between the two adjacent loading switches as a fault section;
7) transmitting tripping control commands to one intelligent feeder terminal unit associated with the fault section; and
8) tripping, via a circuit breaker of the one intelligent feeder terminal unit, the two adjacent loading switches,
wherein each intelligent feeder terminal unit includes one circuit breaker, and wherein the value of n being set as 1.25.

2. The method of differential protection in the power distribution networks based on phase difference principles of claim 1 , wherein the control system transmits tripping control commands through a high-speed fiber optic Ethernet.

3. The method of differential protection in the power distribution networks based on phase difference principles of claim 1 , wherein after the step 8), the method of differential protection further comprising the following step:
delaying a set time; and
putting an interconnection switch into use.

Assignees

• Xj Group Corp
• Xj Electric Co Ltd
• Xuchang Xj Software Tech Ltd
• Jiangsu Electric Power Company Res Institute
• State Grid Corp China
• Xj Electric Co Ltd

Inventors

• Niu Qiang
• Liang Jingwan
• Jiang Shuai
• Qiu Junhong
• Jia Huawei
• Li Meng
• Gao Lei
• Tao Yongjian
• Liu Yongxin
• Li Feng
• Dong Xintao
• Xi Yake

Classifications

• G05F1/66 Primary

  Regulating electric power · CPC title

• H02H3/265

  responsive to phase angle between voltages or between currents · CPC title

• G05B15/02

  electric · CPC title