Evaluation of service aged 35 kV TR-XLPE URD cables

Electrical Degradation of High Voltage Cable Insulation Energized by Switching Impulses

“…The trend of XLPE observed in this experiment is in agreement with the phenomenon reported in [4], [5] and [6], in which the dielectric strength of XLPE cables is determined after several years of aging in the field and accelerated aging in the laborotary. The AC breakdown voltage of XLPE cables decreases at first 500 impulses applied and then increases as more impulses are applied.…”

Lightning protection for aged cable systems — Problems with water trees

“…Data in [4] shows approximately a 50% drop of the TR-XLPE cable insulation impulse strength after two years of service aging. Data in [5] presents a continuous reduction of the impulse strength of 35 kV XLPE cable over its service life, and reports the remaining impulse breakdown strength after 7 years of service at 30% of its initial value All the research above demonstrate that the system impulse strength can degrade significantly as the cable ages.…”

“…Although it is more difficult to estimate the impulse strength of aged systems there has been some work done on this topic. Several reports have indicated that the remaining impulse strength of the cable insulation can drop from 20% to 75% depending on the degree of aging [3,4,5]. A 20% reduction in impulse strength can be typical of cables moderately aged, and a reduction in impulse The calculation examples for protective margins under different protection schemes are given in Figure 2 and 3 with the scenarios of 20% and 40% impulse strength reduction as a result of water treeing, respectively.…”