FIELD: electric instruments. SUBSTANCE: method involves generation of signals of instantaneous power of each phase, their averaging and adding, generation of signal of load power and its conversion to frequency of pulse signal. Then number of pulses is counted taking into account sign of signal of total power of phases. Then method involves generation of absolute values of instantaneous power in each phase. Said sum provides signal of load power. Corresponding device has two adders, zero-level comparator, voltage-to-frequency converter, information processing unit. Channel of each phase has multiplier, low-pass filter, and absolute value calculation unit. Another claim of invention describes method in which signs of averaged instantaneous power of phases are detected, their values are used for sign inverting of corresponding instantaneous power of phases, results are added. Thus average value of result signal is used as signal of load power. Signal of load power is generated simultaneously with its conversion to frequency of pulse signal. In addition in order to achieve this device has integrator and hysteresis- loop comparator, while channel of each phase has controlled inverter, zero-level comparator and XOR gate. EFFECT: protection of measuring result when power of one or several phases is going to be stolen. 4 cl, 5 dwg
