The technical differences between prefabricated substations and combined substations are mainly reflected in their structural design, installation process, operational flexibility, and application scenarios. A comprehensive comparison is as follows:

1. Structural Design
Prefabricated substations typically adopt an all - in - one, fully enclosed structure. High - voltage switchgear, transformers, and low - voltage distribution equipment are integrated into a single pre - assembled box. This design emphasizes compactness and integration, with components pre - installed and wired in the factory. For example, the shell materials often use high - strength steel or composite materials, providing good protection against dust, moisture, and mechanical impacts.
Combined substations, on the other hand, usually adopt a modular structure. Different functional modules, such as the high - voltage compartment, transformer compartment, and low - voltage compartment, are designed as independent units. These modules can be combined flexibly according to specific requirements. The advantage of this design is that it allows for easy replacement and expansion of individual components. For instance, if the low - voltage equipment needs to be upgraded, only the low - voltage module needs to be modified without affecting other parts of the substation.

2. Installation Process
Prefabricated substations are highly pre - assembled in the factory. After arriving at the construction site, they only require simple foundation fixing, connection of incoming and outgoing cables, and commissioning. This significantly shortens the on - site installation time. For example, a small - scale prefabricated substation can be installed and put into operation within 1 - 2 days, making it suitable for urgent power supply projects.
Combined substations, due to their modular nature, require more on - site assembly work. Each module needs to be accurately positioned, and complex inter - module wiring and connection operations are necessary. Although this increases the on - site construction time, it provides greater flexibility in adapting to different site layouts and power requirements.

3. Operational Flexibility
Prefabricated substations have relatively fixed internal configurations. Once manufactured, it is difficult to make major changes to their internal electrical systems without significant reconstruction. However, they offer stable performance in environments with known and unchanging power demands.
Combined substations shine in terms of flexibility. Their modular design enables easy capacity expansion or functional modification. For example, when the power load of an industrial park increases, additional low - voltage distribution modules can be added to the combined substation to meet the growing demand, without having to replace the entire substation.

4. Application Scenarios
Prefabricated substations are often used in scenarios with limited space and urgent power supply needs, such as temporary construction sites, small - scale residential areas, and rural power grids. Their compact size and quick installation features make them ideal for these applications.
Combined substations are more suitable for large - scale industrial parks, commercial complexes, and urban power grid projects with complex power requirements. Their modular design allows for customized configurations to meet diverse load characteristics and grid connection requirements.

In conclusion, prefabricated substations focus on simplicity, quick installation, and fixed - configuration applications, while combined substations prioritize flexibility, scalability, and adaptability to complex power demands. The choice between them depends on specific project requirements, site conditions, and long - term operational considerations.