Large-scale condenser(300 Mvar)has the possibility of stator winding inter-turn short-circuit in practice. It will be a serious hidden danger for the safe operation of the condenser that there is no inter-turn short-circuit protection or the performance of inter-turn short-circuit protection is not perfect. The multi-loop analysis method is used to simulate and analyze all possible internal faults of the large-scale condenser with two different cooling modes. The results show that there is a large dead zone in the existing main protection configuration of the large-scale condenser(complete longitudinal differential protection + longitudinal zero-sequence overvoltage protection). The failure types of longitudinal zero-sequence overvoltage protection is further analyzed

which can provide reference for the performance improvement of the main protection configuration of large-scale condensers.