INVESTIGATION OF SPACE CHARGE AND ITS TRANSPORT PROCESS IN UV AGED SILICONE RUBBER

Summary

Silicon rubber (SiR) insulators are widely accepted outdoor insulator since two decades for conventional High Voltage Alternating Current (HVAC) transmission lines. Though under HVAC transmission line performance wise there are fewer issues but under High Voltage Direct Current (HVDC) transmission space charge accumulation is causing severe tracking and erosion leading to failure of the SiR insulator. The accumulated space charge during processing is affected in outdoor environment by various factors like corona, electric field, dry band arcing, pollution, humidity, temperature and ultraviolet (UV) radiation which leads to material degradation. In this present investigation the effect of UV ageing in SiR is studied by a non-destructive test technique. The technique employed, Thermally Stimulated Discharge Current (TSDC) which revealed thermal relaxation properties in SiR samples. SiR samples with three different percentages of filler loadings are UV aged for 1000 hours as per ISO-4892-2 standard and assessed UV aged and compared with that of un-aged samples employing the TSDC method. The result of the TSDC test indicated that, an increase in the accumulated space charge for UV aged samples as compared to virgin samples. Further the performances of UV aged samples are also assessed subjecting the samples under Direct Current Inclined Plane Tracking Test (DC-IPT) as per IEC-60587 standard with a constant positive DC voltage of 3.15 kV which is equivalent to 4.5 kV AC voltage. A relationship between space charge accumulation and resistance to tracking and erosion is presented. Therefore non-destructive TSDC test following the UV ageing test (ISO-4892-2) could serve as a diagnostic technique to assess long term performance of SiR insulator for outdoor HVDC transmission.

Additional informations

Authors

Merte Ralf, Kolcunová Iraida, Cimbala Roman, Lison Lukáš