Modeling And Solving Of A Complete Analytic Model For Fault Diagnosis Of Power Systems

Rapid diagnosis of fault elements plays a crucial role to speed up the process of fault treatment and system recovery when faults occur in a power system, for the secure operation of power systems. Fault diagnosis of power systems has been being an active research area at home and abroad for many years, but the fault diagnosis problem has not yet been resolved completely till now. The main cause is that fault diagnosis of power systems is difficult to be modeled accurately and be solved exactly considering errors of alarms as well as misoperation and failure operation of protective relays and circuit breakers. In this thesis, modeling and solving the fault diagnosis in a complete analytical form are investigated, and a complete analytical model for fault diagnosis is presented. The complete analytical model consists of a set of logical equations representing the diagnostic rules, of which the variables represent the states of faulty elements, actions and malfunctions of protective relays and circuit breakers. Each solution of the model represents a logically possible fault mode interpreting a complete scenario of fault diagnosis. The modeling, as well as simplifying and solving, of the complete analytical model is investigated systematically, and several technologies of fault diagnosis based on the complete analytical model are developed.The main work of this thesis is summarized as follows:1. A complete analytical model for fault diagnosis of power systems is proposed by complete representation of the diagnostic rules. The intrinsic logical relations between the states of faulty elements and actions of protective relays(&circuit breakers) are reserved, contributing to the improvement of the error-tolerance ability of the analytical model.2. Simplifying and solving of the complete analytical model is investigated systematically. The complete analytical model is a set of logical equations consisting of implicit functions, and no effective approaches to solve such logical equations are available by far. With the exploration of the characteristics of the complete analytical model, a simplified version of the model is derived theoretically using equivalent transformations, relation decoupling and separating the independent variables from the dependent ones. The complete solution set of the complete analytical model is obtained by deduction from analysis of the alarms received.3. A fault diagnosis method based on the complete analytical is proposed with various uncertainties in consideration. The complete analytical model has a multiplicity of solutions because of the uncertainties in the process of fault diagnosis. A composite index denoting the decision-making risk of fault diagnosis is built by considering distribution of the uncertainties. The fault diagnosis problem is then transformed into an integer programming problem of risk-based decision making, and the optimal solution of the complete analytical model can be obtained as the result of fault diagnosis by using a stochastic optimization algorithm.4. An approach to construct the complete analytical model is proposed according to the IEC61850standard. The configuration of protection and the logical relationships between the behaviors of protective relays and circuit breakers can be acquired by analyzing the SCD (Substation Configuration Description) file, and the complete analytical model is constructed on line by combining the topology of the power network with the configuration and relationships acquired above.5. An acquisition method of the real-time information for fault diagnosis is proposed by building an online interface to the SCADA system. A sequence of alarms including information for fault diagnosis is intercepted and captured using a technique so-called "generation of dynamic event window" presented by the thesis. From the captured alarms, the fault diagnosis information is then extracted according to the relevance among faulty elements, protection relay actions and circuit breaker trips.