Multi-step back-to-back capacitor bank switching in a 115 kV substation

This paper presents the simulation investigation of multi-step back-to-back capacitor bank switching in a 115 kV substation of the Electricity Generating Authority of Thailand in order to observe inrush current, peak oscillating voltage and frequency of transient oscillation. Different cases are simulated such as energization of 24 MVAR back-to-back capacitor banks up to 5-step with and without the pre-inserted resistor as well as capacitor bank with current limiting reactor. Then the effects of short circuit current and opening the circuit breaker to de-energize the capacitor bank are investigated. Finally, the interesting case occurring in a practical substation with 5-step back-to-back capacitor bank switching is studied. The results are used to evaluate the severity of electrical stresses in electrical system when such switching operations are performed.