DC filter in the UHVDC project plays such important role as harmonic elimination and high-voltage capacitor bank is easily damaged during the operation of DC filter. It is therefore necessary to calculateand study the setting of the unbalanced current protection action of the capacitor bank in accordance withthe specific configuration proposal in the UHV converter station. In this paper

the percentage calculationmethod of unbalanced current of capacitor at bridge differential protection is deduced on the base of thestructural characteristics of DC filter capacitor in UHV converter station. Then

the unbalanced current percentage of the DC filter capacitor banks under different fault conditions at Shaoshan UHV converter stationis calculated and which is in agreement with the simulation result of unbalanced current under the samefault condition. With such factors as environment and stray capacitance

the setting of the three unbalancedprotection actions are obtained under holding a fixed margin

and it is compared with the measurement ac-curacy of optical current transformer for Shaoshan station and both accuracy and reliability of the unbalanced action is proved. The study contents in this paper have definite reference significance for the unbalanced protection configuration of DC filter capacitor in the UHV converter station.