The misoperation of the high-frequency protections of different types and different sorts has been taken place many times in the 220kV power system in Hunan Province when a breaker was closed surgyly to a transformer or a fault took place at the remote termial of a close-in Line. They in fluenced seriously the correct operating ratio of the relay protection in the 220kV power system. In accordance with this
the paper Analyzed and studied the related problems caused misoperation and puts forward some precautions for reference.