METHOD OF AND DEVICE FOR RELAY PROTECTION OF GENERATOR VOLTAGE CIRCUITS OF DIRECTLY WATER-COOLED GENERATOR- TRANSFORMER UNIT Russian patent published in 1996 - IPC

FIELD: electrical engineering. SUBSTANCE: method involves superposition of AC currents of two frequencies onto generator voltage circuits and determination of equivalent conductance G_eg of insulation and coolant using formula G_eg=(I21

n²-I22)^1/2•(n²-1)^-1/2•K, where I₁, I₂ are superimposed currents of frequencies f₁ and f₂, respectively; n = f₂/f₁ is frequency ratio; K is constant; then dielectric power factor is determined and OFF-operation command is generated in case at least one of these parameters is higher than permissible value. Insulation conductance G_i is determined as difference between equivalent conductance G_eg and coolant conductance G_c. Device implementing this method has two voltage supplies for frequencies f₁ and f₂ connected through potential transformer 1 to generator voltage circuits, current-to-voltage changer 4 whose output is connected to two admittance and conductance square calculating units 10 and 11, respectively. Outputs of the latter are connected through adders 8, 12 and square-root extraction units 13, 14 to inputs of first adder 15 calculating insulation conductance and capacitance, and divider 15 calculating dielectric power factor. Outputs of adder 5 and divider 15 are connected through comparison units 16, 17 and OR gate 18 to input of final element 8. EFFECT: improved sensitivity of protective device; improved validity of insulation parameters calculation results. 1 dwg