Dielectric Measurements on Epoxy Resin Based Insulating and Field Grading Materials under High Frequency High Voltage Stress

Inhalt:
Solid insulating materials are more and more exposed to electric fields with high frequency components. This is due to an increased integration of power electronic components in power grids and the continuous advancement of wide-bandgap semiconductors. The combination of high electric fields and high frequencies can be a more critical stress on most insulating and field grading materials compared to conventional operation at power frequency. This work introduces dielectric measurements on an unfilled epoxy resin as well as a nonlinear field grading material (filled epoxy resin) with frequencies up to 2MHz at field strengths up to 12 kV/mm. As a part of the dielectric measurements, the relative permittivity, the dissipation factor and the dielectric losses are determined. In addition, the stationary operating temperature of the test samples due to dielectric heating is measured. The measurements have shown that the dielectric parameters of both materials depend on field strength and frequency. In addition, the investigations clearly indicated the electrical-thermal limits of the materials as a function of the frequency and the electrical field strength. For both reasons, material characterization with high frequency high voltage can be an important step in the design processes of insulating systems in high voltage technology and power electronics.