A: APPENDIX469 MOTOR MANAGEMENT RELAY – INSTRUCTION MANUAL A–3Once again, if the polarity of one of the phases is out by 180°, the magnitude of theresulting vector on a balanced system will be out by a factor of 1.73.On a three wire supply, this configuration will always work and unbalance will be detectedproperly. In the event of a single phase, there will always be a large unbalance present atthe interposing CTs of the relay. If for example Phase A was lost, Phase A would read zerowhile Phase B and C would both read the magnitude of Phase C. If on the other hand,phase B was lost, at the supply, Phase A would be 180° out-of-phase with Phase C and thevector addition would equal zero at Phase B.
