Study On Criteria For Transient Based Protection For EHV Power Grid

Transient based protection for extra high voltage (EHV) power grid is a concerned research topic for its great significance of theoretical study and value of practical application in recent years. In this dissertation, the principle and algorithm of fast starting, directional, and fault phase selection elements has been studied based on background of transient based protection.The wavelet transform singularity detection is studied, and singularity detection starting element based on wavelet transform modulus sum is constructed. Simulation on ATP program and authentication on measured transient faulted data show that starting element meets the requirement of fault starting—not resist action when fault and not action when no fault.Transient energy directional element based on recursive median filter is constructed according to analyzing the character differences between transient of different fault direction and combining recursive median filter. Simulation on ATP program indicates that the directional element determines fault direction clearly; its performance can endure the influences of various factors, including fault distances, types, inception angles and fault path resitances.The fault feature parameters are extracted, subjection functions and fuzzy rules for identifying pattern of fault and selecting phase of fault are developed from perspective of fuzzy pattern recognition, and comprehensive faulty phase selection element based on stratified fuzzy reasoning is presented. A large number of simulation on ATP program and authentication on measured transient faulted data show that the faulty phase selection element can select fault phase correctly, and its performance can also endure the influences of various factors, including fault distances, types, inception angles, fault path resitances,and is reliable.