Low Frequency High Voltage Source for Diagnostic of Insulation Diagnosis of Electrical Equipment - Design and Simulations

The paper deals with diagnostics methods based on dielectric spectroscopy in frequency domain which are nowadays the research subjects of many researchers around the world involved in diagnostic of insulation systems. There is relatively strong pressure to operators of electrical power systems to increase reliability while reducing a time needed for maintenance. The important instrument for frequency dielectric spectroscopy method is suitable very low frequency (VLF) high voltage (HV) source with sufficient parameters in voltage range, frequency range, low content of harmonics etc. Presented solution of HV source is based on the principal of semiconductor convertors usually used for control of electric drives. The HV source consists of high voltage transformer, semiconductor rectifier and IGBT module in H-bridge connection. The IGBT module is controlled by pulse width modulation (PWM). The application of semiconductor convertors for the supplying of capacitive loads brings higher demands on filtration circuits. This is the reason why a substantial part of design creates multi-stage filter module which ensures desired quality of output voltage. The entire circuit has been debugged in simulation program including the preliminary design of filters that can be adjusted after the practical implementation.