Patent ID: 8680718

Claim:
A method for automatic activation of a backup power source to consumers, the method comprising: measuring a positive-phase-sequence voltage at busbars in the backup power source; measuring, at the input of a primary power source, a value of a rms current in a phase for each of three phases and a value of an angle between a vector of a complex rms current in the same phase and of a vectorial sum of a complex rms voltage between the two other phases at the busbars in the primary power source and a received portion, which is equal to 0-50%, of the analogous complex rms voltage at the busbars in the backup power source; measuring linear voltages at the busbars in a primary power source; and providing a command to switch a power supply to the busbars from the primary source to the backup source if any of the measured voltages at the busbars in the primary power source are lower than a set value, and if, simultaneously, the value of the rms current in a phase and the value of the angle between the vector of the complex rms current in the same phase and of the vectorial sum of the complex rms voltage between the two other phases at the busbars in the primary power source and the received portion, which is equal to 0-50%, of the analogous complex rms voltage at the busbars in the backup power source reach a set range of values, and if the positive-sequence voltage at the busbars in the backup power source exceeds a set value.