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Transformer External and Internal Bridge Connections

A bridge connection can be employed when there are only two transformers and two lines. Bridge connections can be categorized into internal and external connections based on the position of the connecting bridge. Bridge connections offer several advantages: they are reliable, flexible, require fewer electrical components, are straightforward to install, have lower construction costs, and can easily be upgraded to a single bus sectionalized connection.

A circuit breaker is also installed on the connecting bridge, which remains closed during normal operation. This type of connection uses only three circuit breakers for the four circuits, reducing the required number of circuit breakers.

In urban areas, internal bridge connections are the most common type of 110kV bridge-connected substations. These substations typically serve as terminal substations for the 110kV voltage level, distributing electrical energy to urban users at the 10kV voltage level. The two 110kV lines act as backups for each other, with no 110kV through power, and do not include 110kV line protection. They are configured with automatic transfer switching on the high-voltage side according to the incoming line backup automatic transfer scheme.

External bridge substations are often used as interconnecting substations within the 110kV voltage level ring network. At the external bridge circuit breaker, bidirectional line protection is configured, while automatic transfer switching on the high-voltage side is not configured within the station.


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