With the increase of transmission capacity and voltage level

the demand for insulation performance of EHV DC is higher and higher. In the development of domestic ±535 kV DC cable

how to evaluate the electrical properties of insulating materials effectively has become a difficulty. In this paper

the electrical performance evaluation methods of flat samples

model cables and real cables of different insulating materials are studied. It is found that the electrical performance test of flat samples is difficult to characterize the electrical performance of materials after cable manufacturing

which is quite different from the performance test of cable spin slice. However

the model cable is designed based on the principle of equal field strength

and its performance test is closest to the actual cable

so it can effectively reflect the dielectric properties

processability and other comprehensive electrical resistance of cable insulation materials. Therefore

it is suggested to use model cable as a key link in the evaluation between flat sample and real cable

so as to effectively make up for the deficiency of flat sample in evaluating the electrical properties of real cable; In addition

the matching between the conductivity temperature parameter of DC cable material and accessory material is also an important parameter

which is one of the key evaluation indexes to determine whether DC cable and cable accessories can pass the type test.