EFFECTS OF IONIC SOLUTIONS TO WATER TREEING ON XLPE CABLE FOR 22 kV DISTRIBUTION SYSTEM

Underground cables are subjected to ionic moisture conditions after installation and being in long-term services. Moisture causes the degradation of XLPE insulated underground cables by accelerating the occurrence of water treeing. This study is an investigation of the results on the effects of ionic solutions on the occurrence of water treeing ion 22 kV XLPE cable for the distribution system of the Provincial Electricity Authority of Thailand. Two ionic solutions, potassium sulfate (K2SO4) and iron(II)sulfate (FeSO4), have been used in this study. The experiment has been done with 1000 h and 2000 h testing periods at 3 temperature conditions, room temperature, 50 degrees C and 70 degrees C. The experimental results show that the most expansion of the water treeing size occurred on the tested samples after tested at the temperature of 50 degrees C with the K2SO4 ionic solution. In the case of testing with the FeSO4 solution, the most expansion of the water treeing size occurred on the tested samples after tested at the temperature of 70 degrees C. Furthermore, Fourier transform infrared spectroscopy has been used to analyze the trend of the chemical structure changes by considering the absorbance of the infrared spectrum of the C=C bond and the C=O bond. The chemical structure changes agree with the occurrence of water treeing as well.