METHOD TO INCREASE SENSITIVITY OF BACKUP PROTECTION OF ELECTRIC SET TO SHORT CIRCUITS Russian patent published in 2011 - IPC H02H3/08 

FIELD: electricity.

SUBSTANCE: in method, according to which currents are measured in phases of grid, double-phase short circuits (SC) are detected, time count t_act of protection actuation is started, for the time of count availability of this SC is monitored, and as it disappears, count is stopped, and if it is available on completion of count, electric set is disconnected, additionally, after measurement of currents, maximum current i_max is separated out of them, and if double-phase SC was not detected, then its value is recorded into memory intended to store value of maximum current i_hmax of load, and periodically, every time interval t₁, specified operations are repeated; and if double-phase SC is detected, value i_max is recorded into memory, intended to store value of SC maximum current - i_SCMAX, and at certain intervals of time t₂ measurements are continued; after disappearance of SC difference I_P1 of the last values I_SCMAX and i_hmax recorded in memory is found and memorised, difference I_P2 is found between current i_max for current moment of time and the last fixed i_hmax, and if condition I_P2≥k_TUNI_P1 is not met (k_TUN - coefficient of tuning), then count t_act is stopped, and if it is met, then count is continued, and then after time t₂ measurement of phase currents is repeated, i_max current is separated, I_P2 is calculated, condition I_P2≥k_TUNI_P1 is checked until it stops to be met.

EFFECT: expansion of functional capabilities of protection.

2 dwg