Abstract
Development of a simple method for condition assessment of oil filled XLPE terminations An on-site/off-line prototype method for measuring water content at different positions inside oil filled high voltage cable terminations has been developed. The method consists of: 1) Measurement rod with relative humidity and temperature sensors in addition to a conductivity sensor for measuring free water in the bottom of the termination, 2) Characterisation database for three oils for converting relative humidity and temperature to absolute humidity, 3) Wireless unit for data transfer from the measurement rod to a computer and 4) Procedure for doing the measurements.The method proved to be a powerful and very simple tool in estimating the humidity and level of the oil in the termination and also detecting free water. The method was compared with more traditional and time consuming methods taking oil samples from the terminations. The agreement between the laboratory and the on-site measurements were very good. In only 10-15 minutes it was possible to diagnose the condition of the termination with respect to humidity.During the project more fundamental work studying from a provoked leakage of water into a transparent cable termination were performed by master student Geir Birkenes (NTNU) supervised by Frank Mauseth (NTNU) and Sverre Hvidsten (SINTEF Energy Research). The behavior of water droplets during leakage was visually studied and the development of the relative humidity from installed relative humidity sensors in the zero field regions below the cone was monitored on-line. Partial discharge activity (pd) was also monitored and proved that such installations are very robust. PD is not a very good method for detecting water leakage and water content in such devices due to the intermittent and in general very low discharge levels.
