Research On Protection Of Large Generator Unit Connected With Power System

With gradual implementing of’power plant and power grid separating, price competition for grid’and an increasing number of trillion level units, the coordinating generators with network has become an important part of strong power grid construction, and proper configuration and setting on large generator protection related with grid has become an important content of coordinating generators with network. Loss of excitation and out of step are the common failure form of generator, which makes loss-of-excitation and out-of-step protection the most significant aspect of large generator protection related with grid. In this paper, the research mainly involves how to optimize configuration of loss-of-excitation and out-of-step protection in order to achieve coordinating generators with network.Firstly, theoretical process of loss of excitation and out of step is analysed. Then three-machine infinite bus system simulation model of a unit capacity of1000MW is set up by PSCAD software, and loss of excitation and short-circuit fault are simulated. The characteristics of terminal voltage, output current, output active power and reactive power are analyzed, which lay the foundation of optimizing configuration of loss-of-excitation and out-of-step protection.Secondly, the criterions of loss-of-excitation protection are analyzed. This paper takes a power plant as an example. By using PSCAD software, a simulation model is build which involves the three-step loss-of-excitation protection with setting impedance circle as the main criterion, and in versing reactive power as auxiliary criterion. The simulation on the behavior of the loss-of-excitation protection indicates that this loss-of-excitation protection can distinguish among loss-of-excitation failure, system unstable and stable oscillation, and short-circuit failure, which meets the requirement of Guide on Security and Stability for Power System. Combined with the simulation results and in view of coordinating generators with network, this paper optimizes configuration of generator loss-of-excit-ation protection for Jiangsu power grid.Finally, the out-of-step protection of a power plant is taken as an example in this paper. Setting calculation of the out-of-step protection of three components is done. The out-of-step protection of three components model is created in the PSCAD software. And the out-of-step criterion of equal area criterion based on energy is added to this model. The action of the improved protection under different faults is simulated. Simulation obtains that the new out-of-step protection can predict unstable oscillation with sending signals in the first unstable oscillation period. And then it counts the number of sliding pole to achieve a delay action. When loss of excitation and short-circuit fault are not promptly removed, the protection works as their backup protection. While during stable oscillation, it doesn’t respond. Combined with the simulation results and in view of coordinating generators with network, this paper optimizes configuration of generator out-of-step protection for Jiangsu power grid.