Estimation of life expectancy of polyethylene-insulated cables. Final report

Technical Report · Sun Jan 01 04:00:00 EST 1984

OSTI ID:5339398

Srinivas, N N

In order to correlate water tree size and density with cable life and properties and to estimate cable life, an extensive test program was carried out using new, laboratory aged and field aged 15 and 25 kV polyethylene (not XLPE) URD cables. The laboratory aging program consisted of accelerated tests at 60 and 1000 Hz with stresses between 1.4 and 6 kV/mm (35 and 150 V/mil) and test times from 6 to 31 months. All laboratory aged and field aged cables showed deterioration characteristic of water treeing: low ac breakdown, low impulse breakdown, high dissipation factor and the presence of water trees. Ac breakdown (as compared to water tree length, dissipation factor and impulse breakdown) appears to be the most conclusive way found in this project to determine the quality of a field aged or laboratory aged cable. Cable degradation depends strongly on the operating stress and therefore, 15 to 35 kV polyethylene URD cables should be operated at low stress (less than 1.6 kV/mm or 40 V/mil) in order to obtain an increased life. Analysis indicates that the life exponent (n) is about 4 and that the failure rate appears to be related to the ratio of ac breakdown to operating stress. If this ratio is 4 or less, the analysis indicates that the cable will probably be experiencing an unacceptable failure rate (5 or more failures/100 miles/year).

• Research Organization: Phelps Dodge Cable and Wire Co., Yonkers, NY (USA)
• OSTI ID: 5339398
• Report Number(s): EPRI-EL-3154; ON: DE84920289
• Country of Publication: United States
• Language: English

Related Subjects

42 ENGINEERING
420800* -- Engineering-- Electronic Circuits & Devices-- (-1989)
BREAKDOWN
CABLES
CONDUCTOR DEVICES
ELECTRIC CABLES
ELECTRICAL EQUIPMENT
ELECTRICAL INSULATION
ELECTRICAL PROPERTIES
EQUIPMENT
ORGANIC COMPOUNDS
ORGANIC POLYMERS
PHYSICAL PROPERTIES
POLYETHYLENES
POLYMERS
POLYOLEFINS
TESTING