## 2 Materials and Methods
### CFD Numerical Simulation  
#### 2.2.1 Modeling and Computational Domain  
This study conducts CFD simulations using the Fluent software [Ansys Fluent! Fluid Simulation Software Available online: [[https://www.ansys.com/products/fluids/ansysfluent](https://www.ansys.com/products/fluids/ansysfluent)]([https://www.ansys.com/products/fluids/ansysfluent](https://www.ansys.com/products/fluids/ansysfluent)) (accessed on 20 May 2025)].The main transformer room is characterized as a semi-outdoor type that lacks a rooftop cover, which facilitates a spacious area with natural ventilation. The primary objective of this study is to examine the impact of PV arrangement on the wind environment inside the main transformer room. Therefore, the influence of ambient wind and heat sources (transformers) on wind pressure is not considered. The model configuration is delineated in Table 1.  
The substation building in this study consists of four main transformer rooms, each with identical scale and structure. Additionally, the substation exhibits uniform geometric characteristics along the airflow inlet and outlet directions. Therefore, the research model is simplified by retaining only a single main transformer room for CFD simulation, as shown in Figure 1b. The shape of a building typically influences the airflow distribution in its  
\begin{table}
\begin{tabular}{c c} \hline \hline
**Item** & **Parameter (m)** \\ \hline Transformer substation & 80.4 \(\times\) 43.2 \(\times\) 29.6 \\ the simplified model & 20.1\(\times\) 43.2 \(\times\) 29.6 \\ Transformer room & 19.1 \(\times\) 20.0 \(\times\) 29.6 \\ Transformer & 12.0 \(\times\) 8.2 \(\times\) 4.0 \\ Vents & 12.0 \(\times\) 1.5 \(\times\) 0.5 \\ \hline \hline \end{tabular}
\end{table}
Table 1: Geometric model of the computational domain.  
Figure 1: Geometric model: (**a**) the 220 kV transformer substation; (**b**) the simplified model.  
surroundings. When simulating the outdoor wind environment of a building, the three-dimensional model should accurately represent the building's dimensions and intricate details within the height boundary. However, in practical applications, simplifying the computational model of the actual building is often necessary to reduce computational time and accelerate convergence [28]. This simplification involves minimizing the complexity of protrusions and recesses while ensuring that the modifications do not significantly affect the airflow distribution around the building [29].  
In the computational domain, H (height) represents the height of the tallest building within the considered area. The distance between the inlet and the building is set to at least 5H, a constraint that also applies to the outlet boundary and the lateral boundaries of the building. The height of the computational domain is defined as 6H. The external computational domain measures 316.1 m \(\times\) 339.2 m \(\times\) 177.6 m, with the substation positioned at its center, with dimensions of 20.1 m \(\times\) 43.2 m \(\times\) 29.6 m. The substation is located 5H away from the horizontal boundaries and 6H from the top boundary, ensuring compliance with the requirements for computational domain boundaries and the blockage ratio [30].