Usage and applications of petri nets in electric power system protection analysis

The electrical energy demand of our country is rising very fast day by day due to the developments in industry, technology and growing population. Therefore it is very important to sustain continuity within the process beginning with electrical power generation until its transmission to urban areas. Energy transmission lines, transformers and buses are the most important part of the power system. Interfering to an occurred fault in the shortest time is very important for the system efficiency. For this purpose, different protection equipments is developed which detect changing system parameters and isolate broken down part from system during the fault condition. Due to its graphical nature, ability to describe static and dynamic system characteristics and system uncertainty, and the presence of mathematical analysis techniques, Petri nets as a powerful tool, form an appropriate conceptual infrastructure for the modeling and analysis of power systems. Petri nets as a graphical and mathematical tool can be used for modeling and analyzing complex systems which can be characterized as synchronous, parallel, simultaneous, distributed, resource sharing, nondeterministic and stochastic. These types of complex systems exhibit characteristics which are difficult to describe mathematically using conventional tools like differential equations, difference equations. Petri nets as a mathematical tool provide obtaining state equations describing system behavior, finding algebraic results and developing other mathematical models. With respect to other techniques of graphical system representations like block diagrams or logical trees, Petri nets are particularly more suitable to represent in a natural way logical interactions among parts or activities in a system. In modeling point of view, Petri net theory allows the construction of the models amenable both for the effectiveness and efficiency analysis.The task of fault location determination is difficult for relays when multiple faults, failures of protection elements, and false data are involved. In this study, a mathematical model is improved in order to solve this problem and to predetermine failure locations in power systems. Fuzzy Petri Nets which produce more successful results than heuristic methods are used during simulation. Power systems with different structures are discussed in terms of operational and control characteristics. It is aimed to minimize the staff intervention during fault. Truth degree values of high probability of failure locations are obtained in the 14 buses power system which belongs to Northwestern Anatolia network using PIPE2 software during simulation. Simulation of the system for various fault cases have been realized in 14 buses power system. Behavior of the system for each fault and the truth degree values of the protection elements have been calculated. For the determination of fault locations with the improved new Fuzzy Petri Nets approach method, in transformations of constraint and objective functions, instead of approaching support hyper-planes fuzzy approaches are emphasized. Truth degree values have been obtained according to incomplete information from circuit breakers and uncertain alarm information from protective relays. Using truth degree values, the most accurate fault location determinations are accomplished.