Wind turbine generator grounding engineering design
Foreword: With the rapid development of the wind power industry, various operational problems caused by grounding problems are gradually beginning to be exposed. Since the grounding of early wind turbines does not have corresponding industry and national standards, the grounding standards of wind turbines are more confusing, there are engineering reference enterprise standards, and there are also related standards in the power industry, and the selection of grounding materials is also problematic. With years of operation, a large number of wind farm units in domestic wind turbines are currently operating in a high grounding resistance state. This article only presents some of its own views on grounded engineering design.
1. Grounding characteristics of wind turbines
The grounding of wind turbines is mainly divided into two parts: power supply common grounding and lightning protection grounding. The common grounding of power supply is mainly determined by the power supply and distribution and transmission system of wind turbines. At present, the low-voltage end of most wind turbine generators adopts TN-C system, that is, three-phase four-wire system. There are three fire lines and one N-line between the generator converter output and the van substation, and the N-line and foundation reinforcement The cage is connected and actually becomes the NPE line. The lightning protection grounding includes the basic part, and also includes the part of the increased ground net outside the foundation. The general design is to distribute three 60×6mm grounded flat steels as the lightning protection ground wire and the basic ring on the basis, which will actually be the auxiliary of the power N-ground ground and the increase of the basic ground area. From the perspective of lightning protection, the grounding area is increased, and the power frequency grounding resistance is reduced under the premise that the soil resistivity is constant.
2. Grounding engineering design
2.1 Calculation of grounding resistance of wind turbine set
2.2 Calculation of thermal stability of ground wire in AC grounding network under common grounding conditions
2.3 Minimum cross-sectional area selection of the ground wire in the ground network
2.4 Thunder current counterattack of adjacent units during lightning strikes
3. Conclusion
This paper only gives the design model through the theoretical calculation of various geological conditions and engineering problems that may be encountered in the grounding engineering. There are many practical problems in the engineering practice, some of which can be solved by the existing theoretical calculations. Some rely on years of engineering experience to solve practical problems. Since there is no relevant industry standard in the wind power industry, there are still some shortcomings in the design, construction, acceptance and other aspects of the grounding of the aircraft. It is believed that with the gradual development of the industry, the corresponding specifications will be improved.
