Method of and device for insulation monitoring

摘要

Method of and device for insulation monitoring of an ungrounded electric network such as for example DC and/or AC networks wherein an insulation impedance comprising an unavoidable ohmic and capacitive insulation resistance between network and ground exists, in particular such networks with connected rectifiers and/or other converters. A measuring voltage in the form of a pulsed voltage is applied to the network to be monitored between network and ground. Initially an offset DC voltage is applied and adjusted until a possible DC voltage inherent in the network to be monitored is compensated for. A voltage pulse of said measuring voltage is applied to the network between network and ground, and a resulting current or a variable derived therefrom is monitored until a predetermined stage is reached, for example an essentially stationary value. The value of said resulting current or a variable derived therefrom is determined at this stage and used for establishing an evaluation of the insulation impedance of the network. <IMAGE>