Reset Characteristics of Automatic Resetting Type Fault Indicators on Three-Phase URD Systems

The need for reliable fault indication in industrial parks has never been greater than it is today. For the most part, these areas are serviced by three-phase multi-legged core padmount transformers. If single-phasing occurs, a voltage induced in the open leg could cause automatic resetting type fault indicators to incorrectly reset as a result. This paper deals with such a situation and its solution. Studies and tests by Long Island Lighting and RTE determined the magnitude of the incident, its affect on associated equipment, and what new product application information resulted.