Along with the growth of loads, the increase of transmission distance and the composited structure of HVAC and HVDC system, the stability characteristics of modern power system are getting more complicated. NR has established unique three-defense-line to protect the power system from blackout. It can significantly improve the stability of the power gird.

Fault Clearing (The first defense line)

The first defense line consists of accurate and fast protective relays to ensure the fault can be quickly cleared to ensure the system keeping the stability. NR provides reliable and high-speed protection products with innovative DPFC protection elements which can significantly reduce the pickup time to trip the fault. It ensures that the fault is quickly cleared before the system loses the stability.

Load Shedding and Generator Shut-Down (The second defense line)

The second defense line is emergency control for severe contingencies. If the unbalance between generation and load is arisen, the wide area protection will take some measurements, such as generator shut-down, load-shedding, to ensure the stability.

While the stability of the power system is lost after the serous fault is cleared, NR’s unique wide area protection and control system will calculate the power flow and generate corresponding control strategies. Then the control commands are sent to the executing device to take some measurements to keep the stability of the system.

Out-of-step Islanding (The third defense line)

The third defense line is local corrective control such as out-of-step islanding and load-shedding for extremely severe contingencies. If the second defense line can not rescue the stability, the third defense line will operated to avoid the collapse and minimize the loss of load. NR provides out-of-step protection and frequency/voltage control devices to keep the system stability if the second defense line can’t make the system to normal operating state.