Research And Design On Grounding System Of Huizhou Pumped-storage Power Station

Grounding system is very important to ensure a safe and reliable operation of the power system and guarantee the safety of operators and electrical equipment. With the rapid development of China's economy growth, the capacity of the power system expands rapidly, and the short-circuit current into the ground rises; this requires to reduce the grounding resistance in the grounding system. However, the pumped storage power station is generally built in the underground caverns where the rock condition is very good, so the resistivity of the earth is high, the hydraulic engineering work keeps a large range of the power station, and the height difference between the upper and lower reservoir is very big. While designing a pumped storage power station, it becomes the designers'great concern to reduce the grounding resistance effectively in the limited available space where the resistivity of the earth is very high, so as to improve the distribution of the surface potentional and enhance the safety and reliability of the operation of the power station. This paper researches the design proposal of the grounding system in Huizhou Pumped Storage Power Station which gives a reference for the design and implement of the grounding system in Huizhou Pumped Storage Power Station.The paper is mainly divided into several aspects as following:1.According to the characteristic of the pumped storage power station, I, theoretically, make out the physical model and mathematics model of the grounding grid of Huizhou Pumped Storage Power Station, and deduce its integral equation and boundary integral equation by boundary element method. By this way I design the key grounding grid layout, and calculate the grounding resistance of the grounding devices in Huizhou Pumped Storage Power Station, then analyze the effect of each physical quantity, including media boundary, subdivision numbers and the resistivity of the media, on the grounding resistance of the power station, and propose the design method and principle of the grounding grid of Huizhou Pumped Storage Power Station.2. Study the frequency voltage characteristic of control cable, and do test and study on the frequency V-T characteristic of secondary electrical equipment, which can be the basis when confirm the best potential rise value of the grounding grid.3. Separation and voltage equalizing are adopted in Huizhou Pumped Storage Power Station to ensure the operators'safety and the safety of electrical equipment operation. Check the contact potential difference and step potential difference, check the no-action of valve-type arrester 6-10kV, in order to ensure that the grounding grid of Huizhou Pumped Storage Power Station is conformed to the calibration condition.4. Describe the measurement of the grounding grid; verify that the measured value of the grounding resistance is basically in line with the calculation. Both the contact and step potential differences are less than tolerance.