Study On Tansmission Sections In Power System

Along with the improvement of automation science, people is putting ever-increasing requirement on the real time control of power grid. But practical power systems develop to be inter-connected for the sake of economic and security, which makes the static security analysis under the N-1 principle not only impossible, but also needless. The changes of power generation and load in power systems follow some certain rules. Based on these rules we bring forward the analysis on transmission sections which is the core purpose of this thesis.The primary thing underpinning others is the introduction for the basic concepts, significance and feasibility of transmission section analysis. There are three factors who can influence the transfer capability of transmission lines. They are: the power and angle restriction, the thermal restriction and the voltage stability. Essentially, it is a question on the electro-thermal coupling. Depends on different running modes of the system and the components themselves, their transfer capabilities will be limited by one of the three factors. In this thesis the conception of transmission section is defined based on the thermal restriction. The normal and the key sections are distinguished and the necessity and feasibility are analyzed. It also points out that comparing with the traditional static security analysis, the analysis on transmission sections finds out the weakness of the power grid firsthand which improves the efficiency and veracity in power system analysis.The study on algorithms to partition transmission sections of the practical power grid is the keystone of this thesis. The dividing algorithms: the algorithm based on the communicating lines mode, the algorithm based on the distributing coefficient, the algorithm based on natural areas and the flow directions and the algorithm based on graph theory are analyzed firstly. Then simple examples are used to explain these algorithms as well as find out the merits and demerits of them. Based on these works it summarizes in the thesis that the network topology and the grid flow both should be took account in when a practical system is being analyzed. Then a new method which fits practical complex power grids is brought forward. By the method brought forward in this thesis which takes account in both the network topology and the grid flow, we do analysis on the power grid whose voltage equal to or over 220kV in ShanDong power system. Then we do some analysis on the result.In this way, transmission sections are the weakness of the whole power grid and we can also call them the bottle-neck who restricts the transfer capability of the grid. Then the ETC (electro-thermal coordination) theory can be used to improve the transfer capability of transmission sections. When the transfer capabilities of transmission sections are improved, the transfer capability of the whole power grid is improved.