Cable winter construction problems

October 04 23:22:09, 2021

During the construction of low and medium voltage power cables in winter, because the outdoor temperature is below -10°C, the PVC and XLPE insulation and jacketing materials at low temperatures exhibit hard and brittle characteristics, such as accidental accidental accidents during the laying process. Bumps, insulated cores and copper shields are easily damaged. Even if the on-site completion test can be successfully passed after the cable is laid, after the cable is continuously energized in the later stage, the partial discharge will be induced after the capacitor current flows through the damaged part, accelerating the insulation aging, and causing the breakdown of the line. This situation is not prominent in low-voltage cables and stands out in medium-voltage cables. Sometimes, there is no problem in the cable factory test. On-site laying and installation are limited due to various conditions. No measures are taken for the cable. The construction is performed directly in winter. After the laying of the cable, the on-site completion test is all normal, but the subsequent power-on operation occurs for a short time. Faults, anatomical points of failure, appearance without any signs of mechanical damage, but the internal insulation lack severe breakdown and ablation.

In recent years, some newly installed medium-voltage 10kV and 35kV faulty cables have not taken measures to heat the cables at the site due to various conditions, and have been directly installed and installed on site at about minus 10°C during the winter. In the short period of time after the power-on operation, there was a breakdown between the phases and the relative insulation (the time of the incident was 10 days and the duration was about 1 month). After the accident investigation, there was no abnormality in the cable production and factory test. The completion test was also successful (26/35kV power cable exchange 52kV/1h passed). However, there was a short-term power failure (a short period of 10 days and a long period of about 1 month). This is undoubtedly related to the fact that the cable was not heated by the cable during winter construction.

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