Impacts of high-frequency voltage on cable-terminations with resistive stressgradding

Behaviors of insulation system are strongly affected by frequency of the system voltages. In addition to power-frequency voltage, the insulation system could be also exposed to a voltage with frequency on the order of kHz due to application of new HV devices. Insulation failures under HF voltages occur not only because of lower breakdown strength of dielectic material under HF voltage but also because of distortion of field distribution and appearance of hot-spot. A comparison study was carried out on the insulation performance and thermal behaviors of cable-terminations with resistive stressgrading layer under power frequency and HF voltages by experiments and simulations. For HF cases, the hot-spot is generated by high power loss in the semiconducting and field-grading layers due to flowing through of capacitive current. Field enhancement and hotspot increase significantly the failure risk of the cable-terminations.