FIELD: protection of transformers and induction motors against emergency operating conditions in single-, double-, and three-phase ac mains.
SUBSTANCE: phase shifts are evaluated either between current and voltage relative to moment arbitrarily chosen as time reading origin or between phase voltages and currents in any combination thereof. Respective phase shifts are compared with specified limiting deviations. If at least one of relative phase shifts is found to be beyond specified limiting deviations, device generates signal for disconnecting power consumer from supply mains.
EFFECT: facilitated procedure, enhanced precision and speed of response.
4 cl, 4 dwg
