Research On Coordination Of Large Generating Set Relay Protection And Automatic Device

In recent decades, with the rise of economic level, China’s power industry is also growing rapidly. The scale of power system is increasingly large, and while the capacity of generating units, voltage rate are further improving. In the predictable future, China’s power grid is bound to join into a unified whole. How to improve power system security and reliability has become a hot issue of the study at this stage. In recent years, the power grid collapse accident, which caused by such factors as, voltage instability, frequency fluctuations and disturbances, happened several times in a number of large power grids at home and abroad, resulting in large areas of long power cuts and enormous economic losses. In this context, research on coordination between the generating set of relay protection and automatic devices has important significance.Various generator protection should be adapted to changes in operation mode, and achieve the best match with automatic devices, thus ensuring the security and stability of the entire power grid. Early domestic plants do not maintain separate from networks, so this has not been given much attention. Recently, there is also no effective analysis on coordination between abnormal operation of generator protection and system protection. Researches on large generating units involved in the coordination of machine network protection and automatic device at home and abroad are systematically summarized in this article. On the basis of deepening understanding, protection needs of network coordination after developing the domestic power system to the high-voltage, high-capacity, large unit direction are analyzed. And deep research is made for such aspects as low-excitation limitations and loss of excitation protection, over-exciting limit and protection, excitation system parameters setting.The following aspects of the analysis and research are mainly done in this paper:Through study and research, it identifies that PSS configuration in a broad multi-machine power system is feasible. PSS parameter optimization can better suppress system oscillation, in multi-machine power system wide PSS configuration can improve all mechanical and electrical damping oscillation modes, yet not come up with the reduction situation of engineering significance in such mechanical and electrical damping oscillation modes, nor will it reduce excessive non-electrical and mechanical model damping.Based on the establishment of generators and excitation system models, through MATLAB simulation, conclusions have been made: Excitation system magnification times K A mainly affect steady-state output. With the increment of K A, the system gradually began to track the input changes. However, when K A is made too large, System began to emerge oscillation. In addition, with the increment of K A, the rise time and peak time of system are on the decline. Time constant T A has no substantive impact of the system time domain response, only has very minor impact to overshoot.Conversion formula of loss of excitation protection from the characteristic impedance plane to the plane PQ is derived in this paper, and in the PQ plane, loss of excitation protection unit with AVR low exciting limit characteristic action curve is correlated with each other. The tuning problems of low-AVR over-excitation permit limit generator run-time phase are studied. Loss of excitation protection unit can be set with asynchronous boundary, and consider both the co-ordination among low exciting limit prior to loss of excitation protection action.Run-time limitations and the protection of the co-ordination in generators over-excitation have also been researched in the paper, and further clarify the coordination movements order between over-excitation restrictions and the protection, that is, first limit, so that AVR can resume to normal work; when after doing the limiter action , AVR can still not restore to normal working condition, protection by AVR delay acts, yet still can not be restored to normal working condition ,eventually generator relay protection is made to halt.