A NEW RELAY FOR INTERCONNECTED DISTRIBUTION IN THE UK - DESIGN AND FIELD EXPERIENCE

The design of a new microprocessor based multifunctional relay for use on interconnected 33 kV circuits is described. The relay uses sequenc e component principles and rented low grade VF communication. It was n eeded urgently because rented metallic communication circuits, which a re in widespread use, are being withdrawn in the UK. The relay develop ment is unusual because of its measurement methods and because it can derive polarising voltage from existing 11 kV VTs. The time scales req uired were such that development, field trials and installation phases overlapped. The field experience is described.