ACCELERATED PD-AGING OF SOLID INSULATING MATERIALS UNDER HIGH FREQUENCY HIGH VOLTAGE STRESS

Abstract

Due to an increased integration of power electronic components in power grids and the continuous

development of power semiconductors, insulation materials are exposed not only to high electric fields

but simultaneously to strongly increased frequencies. This combination poses greater stress on most

insulating materials compared to conventional operation. Thereby, both, their short- and long-term be-

havior can be negatively affected. Due to higher dielectric losses and the associated heat generated

leading to accelerated aging of the material. The aim of this study is to investigate the aging behavior of

solid insulating materials under the presence of partial discharges at high frequency test voltages. These

results are compared with aging under 50 Hz stress. For this purpose, various long-term studies are

conducted on epoxy resin test samples at different frequencies and voltage waveforms. As test voltages,

both, sinusoidal high frequency high voltages (HFHV) and so-called mixed-frequency high voltages

(MXF-HV) are used. The high frequencies range from 20 kHz to 2.5 MHz. As indicators of the test sam-

ples aging state the change of the dielectric parameters as well as the breakdown field strengths of the

test samples are examined. In addition, the reduction in lifetime due to different partial discharge aging

stresses is evaluated.