Energy-saving Research In Underground Transformer Substation With Ventilationand Air Conditioning System

The city power supply facilities were an important component of urban infrastructure. With the rising living standards and the accelerated construction process of Shanghai to build a world-class modern city, the electricity demand in Shanghai area had a rapid growth and the power supply shortage also got more and more serious, therefore, the city power supply facilities needed to be improved. The ground of downtown had a high commercial value and was very limited, so the site of transformer substation was hard to find. Even after the site was determined, the area of the transformer substation was extremely small, which caused a difficulty of design and coordinate problem with the surrounding environment, which demanded style and landscape of the architecture to be integrated with environment. Seriousness of the situation compelled us to seek new ideas, the construction of large underground transformer substation in the voltage (110 kV,220 kV,500 kV) and the transformer substation combined with civil construction were presented, which could suit the needs of urban development. The Jing'an underground transformer substation (Expo project) was the nation's first 500kV underground transformer substation. The transformer substation had many kinds of equipment, to ensure the safe operation of equipment the cooling load was designed very high. According to the result of the investigation,67.09% failures of 110kV indoor transformer substation room full of equipment were due to heat caused by failure to make timely discharge. And now the large-scale underground transformer substation design standards of ventilation and air conditioning system were lack of appropriate practical experience and reference works. Therefore, it was necessary to simulate the conditions of ventilation and air conditioning system in the underground transformer substation through the appropriate software to find the optimal design parameters, to ensure safe and reliable operation of the equipment used. Research results not only served the project, but also for a similar follow-up project to provide technical support.As the name suggests underground transformer substation was that all the equipment were located underground, but the ventilation and air conditioning systems still needed to exchange heat and mass with the outside world, so this paper mainly studied the underground ventilation and air conditioning system of each equipment rooms, and the interaction between the main over ground air suction port and exhaust port. The primary object to the underground part of study is the largest heat of 220kV main transformer cabin. By using Fluent software, the flow field and temperature field were numerical simulated. The turbulence simulation and temperature term were simulated with Realizable k-s model and the Boussinesq hypothesis, respectively. The result showed the temperature is closer to the actual situation when the radiation conditions were considered. On this basis, the effective area of outlet was changed to optimize the effective area to obtain the best outlet. The simulation result of the flow and temperature fields under different supply air temperature was analyzed. The analysis showed when the temperature is below a certain value, the ventilation air flow rate in the room could be reduced, which made the ventilation program more user-friendly. Other device rooms (reactors, grounding transformer room) were studied with similar process, because the reactor and change rooms were natural air inlet and mechanical exhaust, the simulation results showed that when the outdoor fresh air temperature below a certain value, air could flow into the equipment room under the natural pressure and eliminated the indoor waste heat.Because of the ground part was a large space, so the simulation studied main diffusion path of the exhaust and its impact on the inlet air temperature. When the outdoor environment was simplified, the case of solar radiation factors were also considered, and ignored external factors, by changing the underlying surface (lime, soil, grass), the impact of the underlying surface was analyzed. When external factors were considered, for example, prevailing winds, by trying different methods, changing downcast shaft location and ground planting of vegetation, the diffusion path of the exhaust was optimized. Namely, the exhaust temperature on the influence of the inlet temperature was in the lowest level.