Two different structures of box-type substation

Box-type substations are divided into two typical types according to their structure and components: European box type and American box type.

From the perspective of the structure of the high and low voltage switchgear and the composition of the transformer, this box-type substation is called the European box-type transformer. The metaphor is a house built with high and low voltage switch cabinets and transformers.

Structurally, the load switch, ring network switch and fuse structure are simplified to the transformer tank immersed in petroleum, the lightning arrester also uses oil-immersed zinc oxide arresters and transformer pillows to offset each other, and the oil tank and radiator are exposed to the air. This box-type substation is called the American box-type transformer. It's like hanging a box next to a transformer.

In terms of volume, European box-type transformers are relatively large due to the traditional switch cabinets and transformers installed inside. It adopts American box-type transformer and has small integrated installation volume.

In terms of protection, load switches and current-limiting fuses are used to protect the high-voltage side of the European chassis. When a single-phase fuse is broken, the pin of the fuse is used to switch the load switch at the same time to avoid phase-break operation. The load switch must have the ability to cut off the transmission current. The low-voltage side is protected by a load switch with a current-limiting fuse. The high-voltage side of the American cabinet is protected by a fuse. The load switch only has the functions of switching, switching and cutting off the high-voltage load current, with a small capacity. When a phase fuse appears on the high-voltage side, the voltage on the low-voltage side drops, and the under-voltage protection or over-current protection of the plastic case automatic air switch works, and low-voltage operation does not occur.

From the point of view of product cost, the European style box becomes a high cost. From the perspective of product price reduction, the US box-type transformer still has a large price reduction space. The three-phase five-leg core of the American box-type transformer can be changed to a three-phase three-leg core; on the other hand, the high-voltage part of the American box-type transformer can be changed from the transformer tank to the outside of the tank, occupying the space of the high-voltage chamber.