FIELD: electrical engineering. SUBSTANCE: point of fault is detected by presence of overcurrent protective gear signal in faulty cell and absence of such signal in preceding cell in direction from power supply; faulty cell is registered as zero time grading and first grading is determined in cell by presence of signal in this cell and in zero grading cell; time grading Δt is found from equation 
, where tmax is desired maximum permissible operating time of entire protective circuit; n is maximum number of grading; n = R-1, where r is number of ranks; to is inherent operating time delay of cell; operating time T of each cell found from equation T = to+CiΔt, where Ci- is protective gear operating time grading number; i = 0, 1, 2.... EFFECT: reduced operating time of protective gear due to its adaptation to point of fault. 2 dwg
