Using high-fidelity waveform data to diagnose medium-voltage protection misoperations

Faults and failures are an unfortunate reality on power systems. In response, engineers have developed a variety of means and methods to protect power systems, with the ultimate goal of rapidly detecting and deenergizing circuits when a fault occurs while causing minimal impact to customers. Most of the time this process works reliably, but occasionally misoperations occur. While many microprocessor-based relays record oscillography as an auxiliary function, the quality and fidelity of the data vary substantially. Particularly during complex events, a lack of high-quality data can impede the investigation into the causes of protection misoperations, and their solution. This paper presents multiple case studies where high-fidelity waveform data was used to diagnose medium-voltage protection misoperations, and, in some cases, correct the underlying causes.