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The space charge in dielectric materials is closely related to the aging of insulating materials under DC voltage. In order to further reveal the aging process of ultra-high voltage direct current (UHVDC) dry bushing, it is necessary to study the space characteristics of epoxy resin used in the bushing during aging process. The epoxy resin samples were prepared in vacuum condition. The samples were aged for 24 hours under the dc stress of 60 kV/mm at different temperature (40, 60, 80 and 100 °C). The space charge in the samples during the aging process was simultaneously measured with improved pulsed electro-acoustic (PEA) system. When the temperatures are less than or equal to 60 °C, there are only homocharge accumulations in the sample bulks. When the temperatures are higher than or equal to 80 °C, the homocharge accumulations near both of the electrodes are the same as the conditions at low temperatures at first. Then subsequently, with the increase of aging time, the positive charge accumulation gradually occurs near the cathode at high temperatures. The higher the temperature is, the sooner the positive charge accumulated near the cathode appears, and the larger the amount of the positive charge is. The characteristics of space charge play an important role in distorting the electric field distribution. With the change of the space charge polarity, the position of the maximum electric field in the samples changed.

With the rapid development of smart grid and grid automation level, the intelligent requirements of power switch in the power system are also increasing. One of the main factors that lead to the secondary equipment failed is the transient electromagnetic interference in the process of switching operation. Due to the transient electromagnetic interference(EMI) caused by the operation of intelligent distribution switch, the secondary equipment may not work normally. Especially during the operation of intelligent distribution switch, the burning and reignition of the arc which caused by contacts generate transient electromagnetic field on the disconnected bus and radiate energy to the surrounding space. Therefore, it is of great theoretical and practical significance to research the electromagnetic interference of 10kV distribution switch in secondary control and protection device. In this paper, the finite-integral time-domain (FITD) method is used to calculate the interference of 10kV intelligent distribution switch when it is operating. The calculated results show that the space radiation and coupling interference caused by the arc in the 10kV distribution switch can be ignored because the intelligent distribution switch is a closed container.

As a mature renewable energy technology, wind power is an important form of renewable energy power generation. With the increasing installed capacity of wind turbines, the cluster of wind turbines has become more and more popular in china. Wind farms are usually located in open areas, and the wind turbines always stand out from the wind farm, which make the blade of the wind turbines are easily damaged by lightning. So lightning protection of blades is important for the safe operation of wind turbines. In this paper, a calculation model of multiple wind turbines was established in finite element method. Through simulating the electric field distribution of multiple wind turbines under thunder-cloud background and lightning leader, the effects of factors such as lightning leader positions and blade angles of wind turbines on the electric fields distribution of the turbine blades were investigated, and the lightning shielding effect of multiple wind turbines was analyzed. The results show that the variation of the lightning leader position and the blade angle of wind turbines both have influences on the electric field distribution of multiple wind turbines. When the lightning leader position varies in three typical positions, the electric field distributions on the surface of the turbine blades vary with the angle at different positions. When the lightning leader position was unchanged, the variation of wind turbine blade angle would also affect the electric field distribution on the surface of adjacent wind turbine blades. Furthermore, in clustered wind farms the angles of adjacent wind turbine blades are random, and the lightning shielding effect of multiple wind turbines was analyzed considering the influence of blade angle variation on the electric field distribution of adjacent wind turbine blades in this paper. The research results can be regarded as a basis for analyzing lightning strike characteristics of clustered wind farms.