Scheme Of Current Longitudinal Differential Protection For HV Transmission Lines

The thesis is focus on the protection criteria and CT saturation of differential current protection in HV transmission line.Based on CT saturation at external fault of short line and other special conditions such as 3/2 connection mode will cause misoperation of line current differential protection for EHV/HV transmission line, a novel integrated scheme which has the optimum functions is provided based on several different criteria and adaptive principle in this paper. Simulation results demonstrate that the proposed scheme is superior to the traditional compensation method.The problem of CT saturation is very difficult all at times and this paper makes researches on CT saturation in UHV transmission lines. The CT saturated characteristic and the influence of CT saturated to the current differential protection have been analyzed, and the anti- saturated measures have been proposed.