Application of PLCs for nuclear plant emergency load sequencers

To alleviate operational problems and improve reliability, Florida Power & Light Company (FPL) initiated an electrical enhancement project which implemented modifications to its Turkey Point nuclear power plant 4.16 kV emergency power supply and distribution system (EPS). Each nuclear unit at the Turkey Point plant is a 760 MWe Westinghouse pressurized water reactor. The original design featured shared emergency diesel generators (EDGs) and 4.16 kV busses between the two units. Included in the EPS were the addition of two new EDGs, a new EDG building, diesel support systems, 480 V load centers, bus load sequencers plus numerous components necessary to segregate the electrical system between the two units. This paper describes design considerations for performance objectives, design control, equipment qualification, documentation, verification and validation, codes and standards and the regulatory approval process. The design of the emergency bus load sequencer represents either the first or one of the first applications of PLCs for safety related systems in a US nuclear power plant