LONGITUDINAL DIFFERENTIAL PROTECTION DEVICE OF DOUBLE-WINDING POWER TRANSFORMERS Russian patent published in 2013 - IPC H02H7/45 

FIELD: electricity.

SUBSTANCE: in the device at the outlet of each transformer (TT) there installed are load resistors equal to 0.1-0.2 Ohm (1% accuracy). Voltages from those resistors, which are proportional to currents, are supplied to two channels of an electronic device, where they are in-series connected in high-voltage transformer (HV TT) channel to a low-frequency filter, which is made as per a scheme with zero offset and a precision full-wave rectifier on operating amplifiers (OA); negative pressure from the rectifier output is supplied simultaneously to inputs of an adder and a quick-acting time-pulse converter; output of the same converter is connected to a base of a transistor switching over an amplification coefficient of the output amplifier for tuning-out against excitation current surges; in low-voltage transformer (LV TT) from TT there performed is series connection of the low-frequency filter, a phase shifter, for phasing of currents from HV TT and LV TT and the precision full-wave rectifier on the OA with a controlled amplification coefficient for compensation of difference of secondary currents of HV TT and LV TT; positive voltage is simultaneously supplied from the rectifier output to inputs of the adder and the quick-acting time-pulse converter; the output of the same converter is connected to the base of the other transistor switching over the amplification coefficient of the output amplifier for tuning-out against three-phase SC currents.

EFFECT: possible setting of protection actuation current by four and more times less than at electromagnetic relays at regulation of voltage of transformer under load.

14 dwg