The difference between prefabricated substation and pad-mounted transformer

Pad-mounted transformer is a substation equipment that integrates high-voltage switchgear and transformers and other equipment. It usually uses load switches and current-limiting fuses as power switches, and has the advantages of simple structure, easy operation, small size, and small footprint.

In contrast, prefabricated substation is a substation equipment that separates high-voltage switchgear and transformers and other equipment. It usually consists of transformers, high-voltage switchgear and low-voltage switchgear, and each device is connected to each other through cables or other transmission media.

When choosing box transformer, it is necessary to make comprehensive considerations based on the actual situation to ensure that the selected box transformer can meet the actual needs.

1. Appearance and structure

The appearance of the prefabricated substation is similar to a small building. The high-voltage switchgear, transformer, low-voltage switchgear and other equipment are installed in different compartments. Each compartment is independent of each other and separated by metal partitions, which has good isolation and protection performance.

The appearance of the pad-mounted transformer is relatively compact. The transformer oil tank is integrated with the switchgear. The transformer body, high-voltage load switch, fuse, high-voltage and low-voltage connections are all placed in a sealed oil tank, and the structure is relatively simple.‌

2. Protection method

Prefabricated substations usually use load switches and current-limiting fuses for protection on the high-voltage side, and intelligent circuit breakers and other protection methods on the low-voltage side. Each unit has an independent protection system, which can achieve accurate protection and fault isolation of the equipment.

Pad-mounted transformers use fuses for protection on the high-voltage side. The transformer adopts a dual protection strategy of plug-in fuses and backup fuses. The low-voltage side is usually protected by air switches.

3. Application scenarios

In view of the structural characteristics and advantages and disadvantages of pad-mounted transformers, pad-mounted transformers are suitable for the power supply of multi-storey residential buildings and other unimportant buildings with relatively low power supply requirements. According to our actual use, pad-mounted transformers are fully suitable for the power supply needs of multi-storey residential buildings after being equipped with a small ring network switch station. Because even if the box transformer fails, it will not have much impact on residents. But it is not suitable for small and high-rise buildings.

Prefabricated substations are suitable for multi-storey residential buildings, small and high-rise buildings, high-rise buildings and other more important buildings.

4. Performance

The prefabricated substation has a high level of protection, which can effectively prevent the impact of external environmental factors on the equipment. The equipment has high operating reliability and a long maintenance cycle.

The pad-mounted transformer has a compact structure, relatively difficult heat dissipation, and a slightly weaker ability to adapt to ambient temperature. But it has certain advantages in terms of cost.

5. Cost

The prefabricated substation has complete equipment configuration and high manufacturing process and technical requirements, so the cost is relatively high.

The pad-mounted transformer has a relatively simple structure, high equipment integration, and low manufacturing cost, which has certain advantages in some projects with high cost control requirements.

Both the prefabricated substation and the pad-mounted transformer have various shortcomings. But with the advancement of science and technology, the continuous application of other new technologies such as distribution automation and capacitor compensation in box transformers, box transformers will definitely be the preferred solution in the power supply mode.