Modification of Pulsed-Electro-Acoustic (PEA) measurement system for investigation of the space charge distribution in insulating materials under HVDC with superimposed medium-frequency AC voltage

Abstract:
Due to the use of power converters as a result of the growing role of HVDC transmission, the insulation of electrical equipment is stressed by DC voltage with superimposed medium-frequency (1 to 30 kHz) AC voltage (combined voltage). The possible formation of space charge can result in ageing and subsequent destruction of the insulating material. The traditional Pulsed-Electro-Acoustic (PEA) technique for investigating space charge distributions is unsuitable for combined voltages with medium-frequency AC components due to the unfavorable voltage distribution between the sample and decoupling elements. This paper presents a modified PEA measurement system (electrical circuit, setup, trigger system) for measuring space charge space charge profiles when applying low- and medium-frequency combined voltages (up to 25 kHz). A verification of its functionality is shown using test measurements on polycarbonate.