Controlling strategy and implementation for synchronously closing 550 kV parallel capacitor

Synchronously closing can avoid surge current and overvoltage on the parallel capacitor. There will be more meaningful to 550 kV than lower voltage capacitor because the insulation requirements are relatively higher in 550 kV situations. Circuit breaker´s synchronous operation and synchronously closing controller (SCC) can be a key part to the modern substation intellectualization and automation system in the future. The controlling strategy for synchronously closing 550 kV parallel capacitor has been discussed in-depth in this paper. The main influence factors, such as rate of decrease dielectric strength (RDDS), deviation of closing time of the circuit breaker, and residual voltage on the capacitor, have been considered. The optimized mechanical contact point for synchronously closing has been obtained. Based on embedded technology, a SCC for synchronously closing 550 kV parallel capacitor and fitting IEC 61850 standard has been developed and has passed the 4th rigorous level EMC test. The test results indicate that the SCC has enough accuracy, calculation and reaction speed, and reliability for real application.