Transient high-frequency current characteristics of UHV busbar fault and countermeasures in busbar protection

A frequency-domain research tool for calculating the initial amplitude,phase,frequency and time constant of fault transient components in complicated networks is developed. It is used to analyse the characteristics and laws of 1 000 kV UHV busbar fault transient high-frequency capacitive current. The result indicates that,its frequency depends mostly on system parameters and operating mode,the amplitude depends mostly on fault initial angle and fault transition resistance,and the time constant depends mostly on fault transition resistance,based on which a new principle of harmonic phasor differential protection is suggested. A short data window filter is constructed by phasor approach to extract the high-frequency current phasor from fault current as the operating signal to form the phasor differential protection. Combined with conventional sampling value differential protection,the operating time can be reduced to half AC cycle.