The series compensation device has good effect in improving the power quality of distribution lines and has found wide application in recent years. In view of the feature of frequent fault in the distribution line

the self-protection of series compensation device should be considered in actual operation to avoid the damage caused by over-voltage of capacitor due to line faults. In this paper

a kind of dual protection mechanism based on metal oxide varistor（metal oxide varistor

MOV）and real-time wavelet transform algorithm to detect faults is proposed. In case of short circuit fault in the line

the MOV is used to suppress the voltage at both ends of series capacitor. The real-time wavelet transform algorithm is used to detect system current

identify quickly short-circuit faults and bypass series capacitor and MOV components

which is a series compensation device with dual protection function compensation device.