After preprocessing the sampled measurement of bus bar branch current

the external and internal faults with different current transformer (TA) saturation degrees can be distinguished by calculating the differences between the correlation coefficients of the sampled currents. According to this

a new criterion with self-adaptive restraint characteristic for bus-bar protection is proposed. Based on the instantaneous sample values and integrating information from multiple sample values

the new criterion can distinguish internal fault from external faults with only a short data window to calculate the correlation coefficients. Moreover

the new criterion can effectively restrain the interference of harmonics and frequency variation. The performance of the new criterion has been extensively tested through dynamic simulation. Simulation results indicate that the new criterion can distinguish internal fault from external faults effectively and reliably. The new criterion is insensitive to TA saturation and the protection performance will not be affected even when an internal fault occurs with current flowing out of the bus. Based on the setting scheme of ratio-restraint differential protection

the setting scheme of the new criterion is simple and feasible. Cooperating with the filtering unit (e.g. the morphological filter)

an ideal bus-bar protection scheme is presented as well.