Study On The Adaptive Current Differential Protection For Transmission Line

This paper analyzes the basic characters of several different criterions existing in being - the criteria of whole-current differential protection, the criteria based on fault component vector , the criteria of whole-current differential protection and the criteria based on fault component instantaneous value. Meanwhile various numerical simulations with Electromagnetic Transients Analysis Program (ATP) are made and the results are analyzed on double-end and T transmission lines. Considering all of the four fault types such as one-phase to-ground , two-phase to-ground ,two-phase short circuit and three-phase short circuit occurred in the lines and outside of the lines.The fault impedances are considerd on to-ground fault.This paper put forward the scheme of capacitance current compensation and the method to discriminate CT's saturation based on above. Single differential criterion can't satisfy the special requirements of UHV transmission line for the sensitivity, speed and reliability of protection. In this paper, an integrated scheme that can get the optimal general scheme is provided based on several different criterions and adaptive theory.