Design of an under voltage load shedding scheme

This paper describes the design and development of a controlled under voltage load shedding scheme (UVLS) for protection against fast and slow voltage collapse of the Public Service Company of New Mexico (PNM) transmission system. This UVLS was designed as a technically-effective and economically-viable control-based countermeasure to prevent voltage instability and collapse for low probability events involving the loss of multiple transmission elements. This paper also discusses the effects of load modeling assumptions and summarizes PNM's load modeling and monitoring efforts at the distribution feeder level.