What is the difference between a prefabricated substation and a combined substation?

The main differences between prefabricated substations and Combined Substation lie in their wiring forms, composition of main components, as well as their respective advantages and disadvantages:

1. Connection type：

• Combined substation: Characterized by a compact layout, it is generally equipped with one or two 10KV incoming lines, and the low-voltage outgoing cables connect 4 to 6 transformers, each with a capacity ranging from 500KVA to 800KVA.
• Pre-assembled substation: In the case of a single transformer, there are usually two 10KV incoming lines, with each transformer having a capacity ranging from 500KVA to 800KVA, and up to 8 to 12 low-voltage outgoing cables. If two transformers are configured, the number of incoming and outgoing lines will increase accordingly.

2. Main component composition:

• Combined substation: Consisting of a transformer, 10KV Ring Main Switch, cable plug, and low-voltage terminal box, it boasts advantages of small size and low cost.
• Pre-assembled substation: It integrates equipment such as transformers, 10KV ring main switchgear, low-voltage capacitors, and low-voltage switches, achieving the integration of Type III station equipment and making the box body more compact.

3. Advantages and Disadvantages:

• Combined substation: Its advantage lies in its small footprint, facilitating rapid installation and concealment; however, its disadvantage includes lower power supply reliability, absence of electric motor mechanisms and distribution automation devices, slightly higher noise levels compared to indoor substations, and the potential for civil engineering modifications during capacity expansion.
• Prefabricated substation: Its advantages lie in noise control and low electromagnetic radiation, and it can be equipped with distribution automation, combining the advantages of Type III substation and American-style box transformer substation. Its disadvantages include its large size, inconvenient installation, and potential impact on the layout of residential areas.

 In summary, prefabricated substations and combined substation each have their own characteristics. The choice of type mainly depends on specific project needs, environmental conditions, and power supply requirements.