DETECTION OF WATER INGRESS IN PILC CABLE BASED ON CHANGE IN CHARACTERISTIC IMPEDANCE

Moisture leads to deterioration of oil-impregnated paper. Locating the water-ingress along paper-insulted lead-covered (PILC) cables is a challenge for utilities. This paper proposes a method to detect the water ingress based on change in the cable's characteristic impedance. The impedance variation causes non-homogeneous propagation for high frequency signal along the cable, where signal reflection occurs. This reflection can be utilized for water ingress location. Experiments are performed to verify the principle. A three-core medium voltage PILC cable with about 80 m length is used in the experiment. Water is pressed into the cable insulation via a hole made in the lead sheath. Measurements are performed before, midway and after water ingress. Two approaches are implemented: time domain…