Voltage Bypassing Operations

Distribution utilities know the inherent risks of bypass switching of medium voltage regulators. When bypassing a regulator in any step position other than neutral, dangerous circulating currents can develop due to the voltage across the series winding in parallel with the shorted bypass switch. Conventional distribution protection systems do not adequately protect circulating currents until the regulator, bypass switch, or leads fail and short to ground. This paper Will use case studies to help us understand why the inherent dangers are posed to distribution service personnel and equipment. Though no substation protection schemes are perfect, we will look at the physics of the circuit to determine if some protection schemes are better at protecting field personnel. This would serve to minimize the damage caused when regulators are switched off neutral, and more importantly, enhancing the safety of distribution service personnel while limiting damage to substation equipment.