Correlation Between Electroluminescence and Partial Discharges in Silicone Rubber Used for High Voltage AC Subsea Connectors
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- Institutt for elkraftteknikk 
Processing of oil and gas has been performed on topside installations close to the wells. Inthe future, wells will be further away from the infrastructure and more processing will beperformed on the seabed. This will require more electrical power on subsea installationsin deep waters and far away from the platforms and shore. Large power cables are connected in subsea connectors at the subsea installations. Becauseof its good electrical abilities, flexibility and water repelling, silicone rubber is agood candidate as insulation material in these subsea connectors. As the industry lookstowards deeper sea-levels and more challenging terrain, studies and research must be conducted on the materials to be used in order to estimate operation-time. Life time of thepower system is crucial for the complete subsea processing plant and long term propertiesof the insulation materials must be known. This study aims to find a correlation between partial discharges and electroluminescencein a pre-made cavity in silicone rubber. In total six samples have been tested; three sampleswith a pre-made crack in the surface wall of a cavity and three samples with a smoothsurface wall in the cavity. A molding procedure in addition to a test-procedure of the samples has been found. It has been found a clear correlation between partial discharges and electroluminescencein a pre-made cavity. If the dissipated energy is high, the emitted light is accordinglyhigh, independent of the peak magnitude of a partial discharge. Partial discharges occurfor voltages below 1 kV for all samples. Electrical tree growth was observed to occur at alower voltage level in samples with a pre-made crack in the surface wall of the cavity. Noelectrical tree growth was seen in the three samples with a smooth cavity surface wall. Allsamples showed sign of degradation in the tip of the surface cavity.