GB1224381A - Device for protection of man against electrical shock from electric locomotive contact network, especially in pits and mines - Google Patents

Abstract

1,224,381. Protective arrangements. DONETSKY GOSUDARSTVENNY PROEKTNOKONSTRUKTORSKY I EXPERIMENTALNY INSTITUT KOMPLEXNOI MEKHANIZATSII SHAKHT. 24 April, 1968, No. 19346/68. Heading H2K. In an earth leakage protective arrangement for a locomotive trolley wire system 12, high frequency current from an oscillator 8 is superimposed on the line 12 and a phase comparator 2 provides an output to a control circuit 24 to effect the opening of contactor 15 to interrupt the supply from a rectifier 14 when earth leakage occurs, e.g. due to a person touching a trolley wire. The comparator 2 also provides an output to an amplifier 3 which with a delay energizes control winding 26 of a "self adjusting inductor" 1 to change the impedance of a winding 25 and so alter the parameters of the arrangement that the comparator ceases to provide an output and the contactor recloses unless prevented from doing so by an insulation monitoring device 29. This device comprises a bridge 32. . . 35 with a diode 36 and the trolley wire system connected across one limb 35. A A.C. supply is connected one diagonal and a relay 31 is connected across the other diagonal of the bridge. If the insulation resistance of the trolley is less than a predetermined value, the bridge is unbalanced and the relay 31 is energized to prevent the control circuit 24 from reclosing the contactor. The phase comparator 1 compares the H.F. current flowing through a current transformer 2 with a voltage derived from the oscillator through a phase shifter 9 and a voltage transformer 5.