Study Of UHV Transmission Line Protection Principle And Device

UHV transmission line plays an important role to transport high-power with long distance in power transmission and transformation project, study the principle of its relay protection and design the device which suits our nation condition is one of the most important work of us. The principle of differential protection and distance protection on transmission lines are studied. The distribution parameters'influence on distance protection of UHV transmission lines is simulated, analyzed and discussed. The design of a new digital relay protection device is given at the last of this dissertation.Considering the principle of UHV transmission line protection, firstly, several traditional principles of differential protection are introduced, analyzed and compared in this dissertation. The pilot differential protection based fiber is fit for being the main protection of UHV transmission lines as it owns obvious natural characters and good reliability. Distance protection also has a broad application space as it is not limited by the network topology of transmission lines of power systems. The principle of distance protection is simply introduced and the factors such as the transition resistor, the swing of power systems, the wire-break of voltage loop and the series compensation with capacitance which affect distance protection's action are discussed in this dissertation thenceforth.The influence on protection of transmission line's fault transient is analyzed in this dissertation and an ATP model of 750kV UHV transmission line is constructed and simulated. Simple faults occur on transmission line of different voltage lever are compared, and the distribution parameters'influence on protection when transmission line get single-phase grounded with big resistance is discussed extra. Several kinds of methods such as the capacitance compensate based on normal phasor in power frequency, the capacitance compensate based on Bergeron model and the capacitance compensate in time domain which are used to compensate the capacitive current of UHV transmission line are listed and compared..Considering the development of the protection device, the design of a digital relay protection device which based on Digital Signal Controller (DSC) for UHV transmission line is introduced, the design of hardware, the module and flow of software, the anti-disturbance measure and the configuration of distance protection functions with particular criterion are presented in detail. At the last of this dissertation, the problem should be considered for the device to adapt for application of UHV transmission line protection is pointed out.