Reliability of SF₆ Circuit Breaker Cells and Selection of Switchgear Circuits for 220 kV Substations

The reliability parameters of 220 and 500 kV circuit breaker cells of various types at substations within the Unified National Power Grid have been analyzed in different time intervals. This analysis revealed that the replacement of outdated oil, minimum-oil, and air circuit breakers (CBs) with SF₆ did not lead to a drastic decrease in the frequency and duration of planned downtime for CB cells. This observation is crucial when assessing the reliability of standard switchgear circuits regulated for use in the national electrical networks. The study demonstrates the expediency of deep unification of switchgear circuits with voltage levels up to 220 kV at UPS substations. Instead of maintaining eight alternative standard circuits, it is proposed to use only two: a system with one partitioned busbar system and a bypass busbar system with the connection of (auto)transformers through a fork of CBs (circuit 12N); transformers-buses with one-and-a-half-line connection (circuit 16). At the same time, the latter is the most preferable in terms of reliability, efficiency, and flexibility.