In this paper

the influence of element breakdown of series capacitor on the traditional unbalanced current protection is analyzed. The monitoring method of breakdown in certain two bridge arms of capacitor element is judged through phase comparison of unbalance current. The influence of the breakdown of series capacitor element on the branch circuit current is analyzed further. A method of monitoring the breakdown of series capacitor element at the certain bridge arm is made by way of monitoring unbalance current

branch current difference and total current simultaneously. The actual series compensation device is calculated

the selection method of current transformer in the project

the monitoring step and criteria of the breakdown of series compensation capacitor element are proposed.