Fault Ride-Through trip curves

Over the past decade, new requirements have been proposed and implemented for Fault Ride Through, including a proposed NERC standard that would impose fault ride through requirements on all generation. Most existing fault ride through curves are used in the wind industry. Some have some very unusual-looking trip characteristics that are polygonal in shape, rather than the characteristic rectangular trip curves customarily used by protection engineers. This paper will examine some of these trip characteristics, increasingly common in the wind turbine industry, and show how a rectangular characteristic can be used to satisfy a polygonal trip requirement. The use of common trip curves such as that proposed by NERC in PRC-024-1 may require some changes in generator plant design, as occurred in the wind industry, to insure that equipment is designed for low-voltage operation.