Study on Over Load Protection Inverse Time Lag Property of Large Scale Generation Unit and Improvements

Aiming at difficulties in correct matching of inverse time lag property of large scale generation unit and practical heating of the unit,this paper analyzes differences and connection of logarithmic inverse time movement equation and common inverse time movement equation by deduction of inverse time movement equation of stator over load protection and draws a conclusion that logarithmic inverse time property is more close to practical over load heating process of the unit.According to complicated working condition of large scale generation unit,it proposes improvement suggestions for inverse time movement criterion of stator winding over load protection which solves problem of affection on safety of the unit by heat summation.