Ground Fault, Leakage and Electric Shock Currents in DC IT Systems

Abstract

In the chapter theoretical basis of ground fault phenomena in DC circuits is given. Ground fault transient voltages and current waveforms are shown. Measurements of earth fault current characteristic parameters such as initial value and steady-state value are described. Formulas for evaluation of earth fault and leakage currents are derived. Methods of analytical assessment of electric shock hazard as function of insulation parameters are given. Procedures and systems for earth fault and shock current evaluation by means of experimental measurements both in live networks and in network models are proposed. Network total capacitance to ground together with insulation equivalent resistance to ground determine time constant of currents and voltages transients under earth fault conditions. The last section of this chapter presents an overview of methods of ground capacitance determination with use of waveform recording and calculations.