Analysis on Relay of Large Pumped-storage Unit and Study on Setting Calculation
|School||Huazhong University of Science and Technology|
|Course||Proceedings of the|
|Keywords||large pumped storage power plant setting calculation inverse-time characteristic low forward power protection backup protection|
With the rapid development of power system in China, large pumped storage units are being widely constructed because of their excellent regulation characteristics. In order to guarantee the safety and stability of pumped storage units and power system, it is necessary to set up complete protection configuration, solve major problems of setting calculation based on the analysis of features of pumped storage units and their relay devices, and make recommendation for protection operation.For large generator, the actual thermal characteristic is difficult to match the inverse-time operation equation. The paper analyzed the relation and differentiation between the logarithmic inverse-time equation and the general inverse-time equation by inducing the inverse-time operation equation, and came to a conclusion that the logarithmic inverse-time characteristic is closer to the actual thermal process of large generator than the general inverse-time equation. Because of pumped storage unit’s frequent operation, complex working modes, and shortage of capacity of vibration, the suggestions for improvements to thermal overload protection and negative-phase-sequence thermal protection are proposed to eliminate the threat which is caused by thermal accumulation and 100Hz vibration of stator-core and ensure the safety of the power unit.Low forward power protection is one of the unique protections of large pumped storage unit. According to pumped-storage power plant’s mechanical structure, the power would be easy to oscillate if there is a disturbance in the system and may make the malfunction of low forward power protection. Based on electromagnetic transient simulation and analysis of the hydraulic transient characteristic in pumped storage plant, the paper improved the criterion of the low forward power protection in order to enhance the relay’s ability of anti-interference and sensitivity to serious faults.For self-shunt excitation generator, if there is a fault nearby, the short-circuit current would decay quickly and make the backup protection miss operate. This paper analyzed the principle, configuration and setting of the backup protection in large self-shunt excitation generator by comparing the criterion of voltage restrained overcurrent protection with composite-voltage memory overcurrent protection’s criterion. The paper took some actual self-shunt excitation generators as example to illustrate the particularity of the short-circuit current’s changing process, and improved the setting methods of backup protection of large self-shunt excitation generator.Based on research achievements of this paper, the solution to some improtatn problems which are relative to setting calculation of pumped storage unit had been proposed and being used in actual engineering. During the process of finishing the setting calculation subject of generator-motors and transformers of Bailianhe pumped storage power station, this paper also bringed out a set of complete and strict work specifications which could be applied to setting calculation of large pumped storage unit’s delay.