Abstract: With the increase of voltage grade, the overvoltage levels of UHVDC transmission engineering also increase significantly. The setting of DC control & protection and the parameter configuration of arrester are selected from the perspective of their own choice, so it is needed to study the coordination of control & protection with arresters operating characteristics. The control strategy used for the insulation coordination research on UHVDC convertor station is often simplified control strategy recommended by CIGRE （international council on large electric systems）. The protection timing based on the simplified control strategy also has a certain difference from the practice, which may lead to a great influence on the simulation results of overvoltage and arrester. Based on the practical control & protection strategy in Yun-Guang UHVDC transmission engineering, through theory analysis and simulation, this paper studied three typical over-voltage conditions: AC-side phase-phase switching impulse, the flashover of Y winding bushing at HV valve side of converter transformer and metal loop open-circuit, as well as compared the the influence of different delay of Yun-Guang actual control & protection on the operating characteristics of arresters. In these three conditions, the coordination of Yun-Guang actual control & protection strategy with arresters can meet the operation requirements；there is still a adjustable margin in protection delay, which can provide a reference for other DC projects.

Key words: UHVDC, control and protection, ZnO arrester, switching overvoltage