American Electric Power experience with loop switching in EHV stations using air-break disconnect switches

The authors focus on the loop switching operation inside a substation, which is called local loop switching. Within the local loop there are circuit breakers and disconnect switches that can be used to perform a loop switching operation. The interrupting duty of the air-break disconnect switch is calculated theoretically as a function of the station bus physical arrangement and current flow pattern inside the station. The loop switching capability is experimentally determined for two types of 765 kV air-break disconnect switches. The benefits of loop switching performed with air-break disconnect switches inside electrical substations are illustrated by three examples of actual field experience. The switching procedure involved in these examples is discussed