Protection Considerations for an Improperly Installed On-Load Tap Changer

Abstract

On-Load tap changers (OLTCs) are critical transformer components when automatic voltage adjustment is required, such as in distributed generation systems. In June 2019, a defective OLTC was replaced with a brand new one, and shortly after re-energization, solar inverters started to randomly trip offline. This paper describes the investigation into these random nuisance trips, how proper commissioning could have prevented this issue, and what protection elements are suggested to detect this particular problem.