456 / 2022-03-15 23:08:07

Relationship between long-term withstand voltage and short-term boost voltage of XLPE insulation

long-term withstand voltage,short-term boost voltage,XLPE insulation

At present, the electrical and mechanical properties of XLPE insulation are mostly tested by samples with small thickness (micron to millimeter), which is quite different from the centimeter thickness of polyethylene insulation materials in actual high-voltage DC cables. Even though the electrical and mechanical properties of XLPE insulation of thin sample can meet the test requirements, there is still no systematic research to provide the basis for whether the results of thin sample are consistent with those of thick sample and whether it can be directly used to guide the insulation design in practical application.In this paper, a multi-channel long-term breakdown platform independently designed by the laboratory is used to apply a constant 50kV/mm AC electric field to XLPE samples of different thicknesses, and the temperature is controlled by controlling the oil bath circulation device at 30, 50 and 70 °C, respectively. The withstand voltage test is carried out until the insulation breakdown occurs, and the withstand voltage duration is recorded in time. At the same time, the AC breakdown test was carried out on XLPE samples of the same thickness by means of linear boosting. By analyzing the experimental data, the correlation between the short-time breakdown characteristics of XLPE under high field strength and the long-time breakdown characteristics under low field strength is established.The test results show that the withstand voltage duration of XLPE materials in the process of constant voltage is closely related to the breakdown field strength in the process of linear boosting, and with the increase of thickness and temperature, the duration of withstand voltage is significantly different from that in the process of linear boosting. The breakdown field strength decreases together during the linear boosting process.In this paper, the correlation between short-term breakdown characteristics of XLPE insulation under high field strength and long-term breakdown characteristics under low field strength is established, which can provide theoretical reference for accurately selecting the test electric field strength and breakdown time of XLPE test samples during cable inspection.