Effect of NaCl Solution and Temperatures on Water Treeing Propagation in XLPE Underground Cable for Medium Voltage

Water tree has been studied for many years due to it is the cause of insulation failure in HV Cross-Link Polyethylene (XLPE) cable. The insulation failure was mostly associated with the presence of ionic solutions in water treeing. This paper presents the study results on the effect of NaCl ionic solution and temperature to water treeing propagation in HV XLPE cable. A 22 KV XLPE HV underground cable using in the distribution system of Provincial Electricity Authority (PEA) of Thailand was used as a testing specimen. The study was performed by dip testing specimens in 0.1 mol/L of NaCl ionic solution with difference temperature, i.e., ambient temperature, 50 degrees C, and 70 degrees C, respectively. Testing specimens were subjected to 24 kV 50 Hz during the testing period for 1000 hours and 2000 hours. A comparative study of the effects of relative permittivity, bulk conductivity, and behavior of water treeing was presented. The experimental results show that at ambient temperature of 50 degrees C and 70 degrees C for 1000 hrs. However, for 2000 hrs., water treeing propagation was not similar at 1000 hrs. Such results may be due to the role of the testing period. The trend of water treeing propagation is faster than at 1000 hrs.