METHOD FOR PROTECTING A USER OF A THREE-PHASE ALTERNATING-CURRENT NETWORK AGAINST OPERATING EMERGENCY CONDITIONS AND DEVICE FOR CARRYING OUT SAID MEHTOD

摘要

The inventive method for protecting a user of a three-phase alternating-current network against operating emergency conditions consists in determining actual values of a phase-shift between a feeding voltage and a consumption current(s) in at least two phase conductors, in comparing said actual values with permitted phase-shift values within a range which is determined taking into account the maximum and minimum values of a user's power factor (cos?) and in disconnecting the user from the network when a current value exceeds a specified permitted value range. The inventive device for protecting the user of a three-phase alternating-current network against operating emergency conditions comprises current sensors (4, 5, 6), voltage sensors (7, 8, 9) and a unit (2) for disconnecting in the phase conductors. Said device also comprises a phase shift control unit (16), which is embodied in such a way that it makes it possible to produce a signal that the user id disconnected from the alternating-current network when said phase shift exceeds a specified permitted value range and a synchronising unit (19) whose inputs are connected to the network phase conductors, whereas the output thereof is connected to the phase shift control unit (16).