Measurement of Solubility and Water Content of Insulating Oils for HV XLPE Cable Terminations

Water has been found to be one of the the main causes for some service breakdowns of high voltage XLPE cable terminations in Norway. Therefore, measurements of water content have been performed on oil samples taken from several oil-filled housings in service. In addition, measurements of water solubility of three actual oil types have been performed at different relative humidities and temperatures in order to detect the saturation contents. The results show that high water content in the oils in service can be present, and even liquid water was detected. The measurements of water solubility of actual oils show that condensation of water droplets can occur during service. It is therefore recommended to perform maintenance work on such installations with respect to monitor the water content of the insulating oils.