Title :
Fault location and diagnosis in a medium voltage EPR power cable
Author :
Reid, A.J. ; Zhou, Changle ; Hepburn, Donald M. ; Judd, M.D. ; Siew, W.H. ; Withers, P.
Author_Institution :
Inst. of Eng. & Built Environ., Glasgow Caledonian Univ., Glasgow, UK
Abstract :
This paper presents a case study on fault location, characterization and diagnosis in a length of shielded 11 kV medium voltage ethylene-propylene rubber (EPR) power cable. The defect was identified on-site as a low resistance fault occurring between the sheath and the core. A 43 m section was removed for further analysis. The fault resistance was characterized and the location of the defect pinpointed to within a few cm using a combination of time-difference-of-arrival location and infra-red imaging. A combination of X-ray computed tomography, scanning electron microscopy and energy dispersive X-ray spectroscopy were then applied to characterize any abnormalities in the dielectric surrounding the breakdown region. A significant number of high density contaminants were found to be embedded in the dielectric layer, having an average diameter of the order of 100 μm, a maximum diameter of 310 μm and an average density of 1 particle per 2.28 mm3. Scanning electron microscopy and energy-dispersive X-ray spectroscopy were used to determine the geometry and elemental composition of some initial contaminant samples. It was concluded that contamination of the EPR layer, combined with an observed eccentricity of the cable¿s core and sheath resulting in a reduced insulation gap, may have led to an electric field concentration in the region of the defect sufficient to initiate breakdown. Preventative strategies are discussed for similar families of cables, including more stringent dielectric testing requirements at the manufacturing stage and PD monitoring to detect incipient failure.
Keywords :
computerised tomography; electric breakdown; ethylene-propylene rubber; fault location; infrared imaging; power cable insulation; scanning electron microscopy; X-ray computed tomography; breakdown region; defect location; dielectric layer; electric field concentration; elemental composition; energy dispersive X-ray spectroscopy; energy-dispersive X-ray spectroscopy; ethylene-propylene rubber power cable; fault diagnosis; fault location; fault resistance; high density contaminants; infra-red imaging; insulation gap; low resistance fault; medium voltage EPR power cable; scanning electron microscopy; sheath; size 100 mum; size 310 mum; size 43 m; time-difference-of-arrival location; voltage 11 kV; Cable insulation; Cable shielding; Electric breakdown; Power cables; Resistance; X-ray imaging; Power cable insulation; condition monitoring; dielectric breakdown; power system faults;
Journal_Title :
Dielectrics and Electrical Insulation, IEEE Transactions on
DOI :
10.1109/TDEI.2013.6451336