In order to improve the power grid relay protection operation management ability, there are three ways to monitor the hidden failures in protection system based on Protection Fault Information System (PFIS) i.e. get the device iteself condition by cataloging the self check alarm information, compare the device operating parameters with the reference values online, and analyze the measurement accuracy by homological comparison with other devices. Liaoning Electric Power Grid has realized relay protection online monitoring and condition assessment on PFIS by these methods. The system is running well, which has proved the correctness and validity of these methods and it has high value of popularization.