EXAMINATION AND LOCATION OF PARTIAL DISCHARGE SITES IN SEVERELY AGED UNDERGROUND DISTRIBUTION CABLES

This paper presents the results of laboratory investigations of partia l discharge (PD) in field aged XLPE underground power cables. This wor k was performed under EPRI contract RP-2284-01. PD measurements were m ade on sixty-one cable samples over a three year period. When PD was d etected, the magnitude was measured and a site location was determined . PD site locations were predicted using time delay estimations betwee n PD pulses arriving at opposite ends of the test cable. Fourteen of t he samples tested had detectable levels of PD. Some of these PD sites extinguished during the measurement period and were retumed to rated v oltage aging. When samples had continuously active PD sites, they were either dissected or retumed to the aging test. Four sites of this typ e were found allowing two for dissection and two for aging. Seven of t he samples failed after PD measurements. All seven failed near the pre dicted PD location. During the PD testing, no test cables contained PD which initiated at or below operating voltage. When PD detection equi pment was monitoring cables which failed, the failures occurred from 2 to 80 minutes after the presence of PD pulses was detected.