A new relay for interconnected distribution in the UK/spl minus/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 sequence component principles and rented low grade VF communication. It was needed urgently because rented metallic communication circuits, which are in widespread use, are being withdrawn in the UK. The relay development is unusual because of its measurement methods and because it can derive polarising voltage from existing 11 kV VTs. The time scales required were such that development, field trials and installation phases overlapped. The field experience is described.<
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