Suzhou: Optimize the hierarchical protection of distribution networks and quickly isolate faults

"10 kV eleven-polder line phase short circuit fault, please arrange personnel to the scene as soon as possible to deal with it
.
" At 18:32 on July 17, Geng Donghai, a shift worker in the dispatching and control sub-center of Jiangsu Zhangjiagang Power Supply Company, sent a line fault alarm information
to Chang Zhijian, a shift member of the distribution and transportation inspection center of the company, through the main station of power distribution automation.
Chang Zhijian immediately summoned Wang Gaobin and other 3 team members to the scene to deal with the fault
.

The 10 kV 11th polder line mainly undertakes the power supply task of 104 customers in Sanxing Street, Jinfeng Town
.
Due to the installation of graded protection switches on pole 16-1-2 and pole 28 in the middle section of the eleventh polt branch, the switch tripped, and the fault did not affect
the power consumption of other customers on the line.

At 19:45, after on-site investigation, the emergency repair personnel found the fault point in the No.
31-1-1 pole - affected by thunderstorms and windy weather, the drop fuse of the branch line broke
.
At 20:47, the fuse was replaced and the whole line resumed power
transmission.

In order to ensure the reliable supply of power during the peak summer period, State Grid Jiangsu Electric Power Co.
, Ltd.
adheres to the principle of "restoring power first, repairing later" in distribution network operation and maintenance, reasonably formulating fault finding and emergency repair strategies, and quickly restoring customer power supply
by improving the accuracy of distribution network operation and maintenance.
Optimizing the hierarchical protection strategy of the distribution network is one of
the measures.

On June 6, the real-time verification and push function module of graded protection switch trip event led by State Grid Jiangsu Electric Power was promoted and applied
in each distribution automation main station of 13 prefecture and city power supply companies in the province.
The module can determine whether the line is in normal operation according to the historical operation record, and determine whether it is a real trip event according to the change characteristics of the switch current sampling value before and after the fault, so as to automatically eliminate interference information such as remote signal jitter and terminal testing, capture the real hierarchical protection switch trip record caused by the fault, generate event information, and timely push it to power supply services and operation and maintenance personnel
.

Suzhou Power Grid is the largest prefecture-level urban power grid in China, with 8,239 10 (20) kV distribution lines, serving 6.
5 million customers
.

According to the traditional distribution network protection strategy, a failure of a customer-side line will cause the entire line where the customer is located to trip, affecting the power consumption in non-fault areas and affecting the reliability
of power supply.
During the peak summer this year, Suzhou Power Supply Company carried out a special action for the hierarchical protection application of 10 (20) kV distribution network lines, adjusted the distribution network protection strategy, and realized the local isolation of the customer-side and branch-side faults through the time-level difference of the distribution network switch, and controlled the customer range affected by electricity consumption to the smallest area
.

At present, Suzhou Power Supply Company has renovated 4,091 distribution network graded protection lines, the graded protection switch has been successfully operated 356 times, and the average fault recovery time has been shortened from the original 30 minutes to 120 seconds
.

The hierarchical protection strategy of distribution network also helps emergency repair personnel to lock fault areas, reduce the difficulty of troubleshooting faults, and shorten the power supply restoration time
.
"In the past, there was no graded protection switch installed on the distribution line, and after a failure, we needed to start from the outlet end of the substation and check the entire section of the line
.
" Chang Zhijian said, "Now we only need to patrol the line downstream from the tripping graded protection switch, which can lock the fault point faster, and the inspection time is cut in half
.
" ”