IEEE ICHVE 2022 / 1-PAGE ABSTRACT

Space Charge Behavior in DC and Low Frequency Transmission Cable Insulation

YANG Jun, WU Jiandong, YANG Fanfan, YIN Yi

Shanghai Key Laboratory of power transmission and power conversion control, Ministry of Education (Shanghai Jiaotong University), Minhang District, Shanghai, 200240)Author email

lysklide@sjtu.edu.cn

The low frequency transmission technology has received extensive attention due to its unique advantages in recent years. Through the application of the low frequency transmission system, when the transmission frequency is reduced from 50Hz to 50/3Hz, the cable current carrying capacity can be increased and the reactive power compensation requirement can be reduced, but the space charge accumulation problem inevitably needs to be considered in the power transmission system. Current researches mostly focus on charge transport in cable insulation under DC electric field, but the distribution and transport of charge in cable insulation during low frequency transmission is still unclear due to the limitation of AC detection technology and resolution. In this paper, Space charge behavior characteristics in both DC and low frequency transmission scenarios are investigated.

The internal space charge distribution test of the insulating material adopts the Electroacoustic Pulse (PEA) space charge test system: put the sample into the equipment to pressurize, the pressurization time is 600s, and the sampling interval is 3s; the space charge under the low frequency AC electric field (50/3Hz) is measured by the improved PEA test method of automatic equalization phase shift (AEPS) realizes space charge test with high phase resolution of 1.8°.

Under the DC electric field, the upper and lower electrode sides of the sample accumulate homocharges; in the case of low frequency, the upper electrode side mainly distributes hetrocharges under the low field while the lower electrode side accumulates homocharges mainly with few hetrocharges. With the gradual increase of the electric field, homocharges of the lower electrode appeared inside the sample, and the charge accumulation at the electrode-sample interface and the internal area gradually increases.

Compared with High Voltage Direct Current (HVDC) transmission, the amount of space charge accumulated inside the cable insulation is less in the case of Low Frequency transmission. Due to the alternation of positive and negative cycles in the low frequency electric field, the charge injection and extraction are faster than under DC, resulting in less internal charge accumulation.