Impact of grounding and filtering on power insulation monitoring in insulated terrestrial power networks

Insulated terrestrial power networks are used for reliable systems such as large production plants, hospital operating rooms and naval ships. The system is isolated from ground and a first fault, such as a short circuit between a phase and ground, will not result in disconnection of the power via residential current devices. The power system does however have to be monitored to measure the fault and correct it, before a second fault occurs. The disadvantage is the maximum capacitance to ground which is allowed because the detection of a first fault to ground is interfered by those capacitances. In modern electronic systems many power line filters are used, increasing capacitance to ground, which is posing a big constraint in the design. Several power insulation monitoring devices have been evaluated and the impact of power line filters has been analyzed to see how much capacitance to ground can be tolerated in practice without impairing the first fault detection.