EHV Breaker Rated for Control of Closing Voltage Switching Surges to 1.5 Per Unit

A 550 kV circuit breaker has been developed which demonstrates the feasibility of meeting the anticipated stringent switching surge limitation of UHV transmission systems of 1100 kV and above. This improved circuit breaker with two-step resistor insertion and a timed closing system limits switching surges to 1.5 per unit in 98% of the closing operations with a maximum of 1.65 per unit. The paper contains a description and the results of verification tests of the circuit breaker and the timed closing system which made meeting these requirements practical.