Ground Insulation Measurement in AC IT Systems

In the chapter there is presented general information on physical nature of network-to-ground insulation. Sense of “insulation equivalent resistance” parameter is explained. A method of insulation resistances-to-ground of single phases and insulation equivalent resistance determination is presented for de-energized AC IT systems. Procedures of insulation equivalent resistance and total capacitance determination in live networks are described. Detailed description of few methods of single phases insulation parameters (i.e. resistances and capacitances) determination in both single- and three-phase systems is given. Several unconventional methods of insulation parameters measurement are presented. Attention is paid to ways of ground fault, ground leakage and possible electric shock currents analytical evaluation and practical measurement. Influence of insulation parameters on these currents levels is discussed. Ground fault current compensation problems are dealt with.