Fault Diagnosis Of The Thermal Equipments Based On The Dynamic Characteristics Of The Control System

With the development of the power industry, the parameters of the generating set are improving gradually, and the capacity is increasing constantly and the systematic complexity improves rapidly. The relevancies and coupling between the different equipments have become more and more close. The requisition for security and reliability of the power system is higher and higher as a result the identification and fault diagnosis(FD) of the equipments in the earlier stage is the hot problem to be solved all the time. The common FD methods are to capture the state signs of the equipments to identify the fault directly. But a lot of status information acquires difficultly for the measure problem and the difficult to identify the corresponding relationships between the faults and their signs. This paper analyses and summarizes the various kinds of ways of FD, which points out the limitations of these methods. Based on the analysis, this paper puts forward the concept of FD based on the dynamic characteristics of the equipments' control system. Meanwhile, the principle of this method and the feasibility of applying to the power plant are demonstrated.This paper takes executive equipment of electronic-hydraulic(EH) servo valve in the introducing 300MW generating unit's DEH that mostly happens the jam fault in the operating as the researching example. The mathematics model of the EH servo valve is set up and simulated in the MATLAB. The dynamic characteristic of the EH servo valve is shown and lay the foundation for the further research of the jam fault.The method of FD based on the magnitude of the flutter signal is presented, which thought derives from the FD based on the dynamic characteristics of the equipments' control system. This paper simulates how the additional flutter signal impacts on oil pressure and actuator output when the dead zone is kept. The proper principle of flutter signal for jam diagnosis is given. Based on the given flutter signal, different jams caused by jam of the EH servo valve under different operating condition are simulated and the output of the oil pressure and actuator are presented. Meanwhile, waving threshold of the oil pressure for jam diagnosis is given. The simulations and analysis prove that the jam fault identification of the EH servo valve based on flutter signal is feasible.The new breakthough is put forward for the equipments' fault diagnosis based on this paper's study.