Some relay quantities for pilot-wire protection

A reappraisal is made of multiterminal private pilot-wire protection. Pilot-wire relay operating and bias quantities are analysed separately. Possibilities of compensation to make relay quantities completely independent of pilot-wire characteristics for a multiterminal protection are examined for both circulating-current and opposed-voltage schemes. Practical methods of achieving such compensation are outlined. Discriminating margins for multiterminal protections are considered, and a basis for optimising the design of a 4-wire multiterminal private-wire protection is set out. An assessment is made of alternative schemes.