First pilot project for regional 'third defense line' put into operation

The first "third defense line" for regional coordinated control has successfully completed its operation recently in Suqian, Jiangsu province, said its operator State Grid Suqian Power Supply Co.

The third defense line serves as the "lifeline" of the power grid's security.

"In order to ensure power supply during winter months, higher requirements are placed on ensuring electricity for people's livelihood, prompting us to strengthen technical support to enhance the grid's defense capabilities against unforeseen situations in extreme conditions," said Fan Bei, a specialist at the power dispatch control center of the State Grid Suqian Power Supply Co.

The preliminary phase has already achieved "observable and measurable" centralized low-frequency load shedding devices in substations. While on the load capacity side, based on mixed connections of sources and loads in low-voltage distribution networks, the power supplier has developed distribution terminals with low-frequency load shedding capabilities.

These terminals can cut off the load ports of the third defense line from the substation terminal, eliminating entire feeder lines and moving the separation point forward to the distribution line users, significantly improving the precision of load control, said the power supplier.

"We have developed eight such distribution terminals, which can solve the problem of precise load shedding and add a firewall for residential electricity supply," said Fan.

In addition, an upgraded third defense line for main station system has also been carried out, including automated generation of low-frequency load shedding strategies, smart identification of active lines and remote value-refreshing for low-frequency load shedding terminals.

Through intelligent inspections on the main station side, it is easier to identify hazards for lines and finally achieve "observable, measurable, and controllable" operations for different types of low-frequency load shedding devices, it said.

lijiaying@chinadaily.com.cn