Standardization of Distribution Protection System Based on the New Generation of Microprocessor Relays

AEP's distribution protection systems which generally include transformers, bus bar, feeders and capacitor banks on low voltage levels, and vary in applications such as fuse saving scheme, high set IOC restoration/lockout scheme, UV load shedding scheme, X'^mer high side circuit switcher and low side circuit breaker control scheme, and bus-1 shot operation (reliability consideration) scheme, to name a few, pose constant challenges to relay protection engineers in designing standard protection and control (P&C) schemes. The new generation of microprocessor relays offers enhanced protection, control and automation features such as flexible programming, programmable pushbuttons and non volatile latches etc. to replace traditional breaker controls, cut-in/cut-out switches, metering, and annunciation panels etc. These new elements/functions provide new opportunities to P&C engineers in developing standard P&C schemes for their distribution system in one relay box. This paper describes in detail the innovative design stages of the development of standardized distribution P&C solutions based on the new generation of microprocessor relays. Each standardized distribution P&C solution offers a complete set of elementary drawings, relay setting templates, relay application guide and relay point list assignments for SCADA. This paper will also present detailed case studies of how AEP leveraged the new generation of microprocessor relays to successfully implement standardized P&C solutions across its various regions of operations and practices