Insulation monitoring method for unearthed electrical network uses pulses AC voltage applied between network and earth and evaluation of measured current values

摘要

The insulation monitoring method has a pulsed AC voltage connected between the unearthed network (1) and earth, with calculation of the ohmic insulation resistance from the difference between successive measured values for the measuring current. A time constant for the network is determined for each pulse voltage value, with measurement of the measuring current at a multiple of the time constant and comparison with a control value for detection of measuring errors. An Independent claim for an insulation monitoring device for an unearthed electrical network is also included.