Consideration of Bus Protection on Gas-Insulated Switchgear, A Three-Phase Fault Case Study

One design benefit of gas-insulated switchgear is its sealed bus design that reduces the chance of bus short circuit fault. Since the costs of implementing a bus protection scheme can be significant, engineers sometimes forgo designing a bus protection scheme for gas-insulated switchgear due to its robust design. This paper reviews a special case of a three-phase fault on the bus of a 34.5 kV gas-insulated switchgear that did not have a dedicated bus protection scheme. The sequence of events, impact, and root causes are outlined as a case study. From the findings revealed in the incident, bus protection was re-evaluated for installation on the existing gas-insulated switchgear. Retrofit options are presented and compared to each other in terms of effectiveness, complexity, and cost.