Research On The Electric Field Distribution In HVDC Cable Terminal And The Design Of Test Terminal

High voltage direct current(HVDC)transmission has distinct advantages in long distance and large capacity power transmission,and it is an excellent technical means to realize the goal of optimizing the allocation of power resources of “electric power transmission from West to East,electric power exchange between South and North,and interconnection in the whole country” in our country.Among the many factors that cause the failure of the power cable system,the failure of cable terminal occupies the largest proportion as the basic structure of the power cable system.When DC voltage superposition pulse is applied to the cable terminal,the interface between main body insulation and reinforced insulation is easy to gather space charge,leading to the local electric field distortion and the breakdown of the insulation in severe,which limits the development of DC cable system to a certain extent.Different tests are needed to be carried out before the application of DC cable,and the use of inappropriate cable terminal is likely to cause erroneous results.In previous tests,trade terminal is usually adopted.However,it can not be used repeatedly and the cost is relatively high.So,we need a kind of reliable,convenience and economical test terminal to conduct testing of DC cable.To sum up,it is of great practical significance to develop reasonable DC cable terminal and test terminal.The COMSOL Multiphysics simulation software was used to calculate the electric field distribution in the cable terminal with different silicone rubber as reinforced insulation and cross-linked polythene(XLPE)as main body insulation,and the combination of reinforced insulation and main body insulation was optimized.It was found that the electric field distribution in the cable terminal was more reasonable when SiO2/XLPE composite insulation was used as the cable main body insulation and ordinary silicone rubber was used as reinforced insulation.Next,the electric field distribution in the steady and transient state was simulated.The simulation results showed that the electric field distribution in the cable terminal was reasonable to meet the requirement under the load cycle test voltage,lightning pulse voltage and operating overvoltage.Then,load cycle and impact voltage tests were performed on the cable terminal.During the tests,there was no breakdown and flashover phenomenon in the cable terminal,which indicated that the cable terminal with the insulation composite had excellent long-term reliability and met the operational requirements.HVDC cable test terminal with grading rings,oil filled and stress cone was designed,and the simulation model was established respectively in this paper.The electric field distribution of HVDC cable test terminal in the steady and transient state was simulated using COMSOL Multiphysics software and the results indicated that the test terminal could obviously improve the electric field distribution at the end of the cable outer shielding,and the electric field distribution in the test terminal and the cable end was reasonable.