DEVICE FOR LEAKAGE TEST AND SHUTOFF PROTECTION Russian patent published in 2013 - IPC H02H3/17 

FIELD: electricity.

SUBSTANCE: source of DC measurement current is connected to grounding terminal through two parallel circuits; at that one circuit consists of the first additional resistor and normally closed contact of voltage relay connected in-series with the above resistor; the second circuit consists of the second additional resistor, diode connected in direction of measurement current passage and normally open contact of voltage relay connected in-series; alternating winding of compensatory choke is shunted by an additional capacitor. Out of two measurement circuits one is on when the other is off thus providing possibility to set setting for the device in each mode and to ensure required characteristics of the device in each mode; at that intrinsic safety of these circuits is ensured at voltage of measurement current equal to several hundred of Volts as it is required for protection devices in mains with voltage of 3 kV and more.

EFFECT: improving intrinsic safety.

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