The vacuum system fault of steam turbine No.2 of L Power Plant in Indonesia was introduced.The reasons caused the vacuum system fault were diagnosed and analyzed.Using the filling water method and the Helium mass spectrum leakage detector to find the leakage point of the vacuum system,the especially big leakage point was found in lower half casing of low pressure cylinder.The effective measures were adopted,and the condenser vacuum leakage fault does not occur again.
