FIELD: instrumentation engineering for electric- traction vehicles. SUBSTANCE: for measuring insulation resistance of any pole of power circuit to ground measuring voltage is applied to power circuit through series resistor inserted between ground and non-checked pole of power circuit. The latter pole is placed at measuring-voltage potential of same polarity as that of operating voltage across pole under check. Transient process is ceased at no voltage across insulation resistance of non-checked pole by adjusting voltage between the latter and ground. Source current and voltage across pole under check are measured and insulation resistance of power circuit pole under check relative to ground is calculated; to this end measured voltage is divided by measured current. Insulation resistance measuring device has measuring voltage source, limiting resistor, indicator, metering circuit shaper, microprocessor unit, two voltage sensors, and two current sensors. Proposed method provides for more comprehensive diagnostics of power mains and for continuous in-service measurements of insulation resistance. EFFECT: enhanced reliability, speed of response, fire and electric safety. 2 cl, 3 dwg
