FIELD: electrical engineering; check of insulation of circuit sections which affect electrical and fire safety of power plants with grounded neutral. SUBSTANCE: summary insulation resistance is measured by means of milliwattmeter and millivariometer with scale calibrated in kilohms and current winding connected to secondary winding of zero-sequence current differential transformer which supplies current asymmetry voltage of phase-working zero loop. In this case, multi-phase circuits should be preliminarily set to single-phase mode of operation with the aid of auxiliary switching apparatus which closes circuit of one of phase power contacts of common contactor in network section to be disconnected for measurement period. EFFECT: simplified measurement process and design of device and reduced mass and dimensions of the latter. 2 cl, 1 dwg
