Research On Adaptive Residual Voltage Compensation Method And Prevent Asynchronous Sampling Measure

The thesis is focus on the research of distance protection and current differential protection in EHV&UHV transmission line. The significant achievements are as follows:Firstly, in cognizance of grounding fault at the weak-infeed side, carried out a detailed analysis of the current, voltage and measured impedance. And present a new residual current and voltage compensation method based on the current and voltage magnitude of each phase for Mho elements. It has been shown that the above compensation manner may have positive impact on the distance protection.Secondly, a new measure to prevent current differential protection maloperation is presented in the paper. This measure is based on phase difference, in connection with the maloperation which is caused by asynchronous sampling. It has been shown that the measure is an effective method.Finally, the characteristics of CT saturation and the impact of CT saturation on the secondary current have been analyzed. And provide a theoretical basis to the engineering practice about how to determine CT saturation state.