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To meet the special insulation demand of the DC transmission system with the highest voltage in the world, a new kind of ±1 100 kV DC voltage divider is designed. The reliability of the new structure voltage divider under the action of lightning impulse is studied. To achieve the voltage and electric field strength distribution of the voltage divider, a 3D transient electric field calculation model is established and a lightning impulse test for the prototype is carried out. The results reveal that (1)The voltage and electric field strength distributing on the voltage divider changing with time show a cumulative effect. (2)The maximum electric field strength occurs at the junction where the first grading ring connecting to the internal bushing. (3)The maximum current of resistance occurs at the peak voltage of lightning impulse with the corresponding time is 1.2 µs. (4)The voltage distributing on the capacitance imply that the capacitance really does play the role of equalisation voltage when the voltage divider suffering lightning impulse. (5)The prototype of HVDC voltage divider passing through the lightning impulse test successfully strongly demonstrates the correctness and reliability of the new structure ±1 100 kV voltage divider voltage.

This paper focus on the research about the probability and practicability of 330 kV GIS structure design with three phase in one tank， which represents the miniaturisation and compact developing trend of GIS. The design principle is proposed according to the volume of three phase in one tank (structure A) is generally smaller than that of the sum volume of three single phase (structure B). Then, the dimension size of 330 kV GIS with structure A is presented. To solve the weak insulation-level problem between phases of structure A, which prevents it from being used in high-voltage power system especially above 330 kV, an electromagnetic-temperature-flow multi-physical field coupling model considering eddy effect and skin effect is established to analyse the influencing factors on the insulation level of internal GIS. Therefore， the insulation level between the phases of structure A is calculated under the condition of power frequency and short circuit, respectively. The results show that the insulation margin of 330 kV GIS with structure A is enough and completely meet the insulation requirement of GIS. Furthermore, compared with structure B, structure A has lower temperature rise and energy consumption.