Partial Discharges in Low Voltage Switchgears at Elevated Temperatures

Usually, the focus of investigations on low-voltage switchgear lies on contact and switching behaviors. Due to increasing power densities, optimization in design or shared operation in frequency converter application (such as in multi- motor applications), switching devices are submitted to increased thermal and / or electrical stress. For certain conditions, the effect of partial discharges, which is well-known for high-voltage applications and components, already occurs at operating voltages in the low-voltage range. Hence, the focus lies also on polymeric materials for dimensioning switching devices.In order to localize potential sources of field enhancements and partial discharges, the focus lies on numerical field strength calculations by means of the entire conductor path geometry in switching devices. To consider the PD behavior on main contacts during a closing switching operation, analytical field strength calculations are done by means of the Schwaiger factor. Finally, measurement results of three selected low-voltage switchgears are presented to evaluate the PD phenomenon at 1 kV and 150 °C.