Between the two groups of buses, every three circuit breakers form a string. Each string connects two loops. It is equivalent to each half circuit breaker with a loop, so it is called one and a half circuit breaker wiring, also known as 3/2 wiring. In one and a half connection mode, three switches between two buses are connected in series to form a string.
In a string, the outgoing circuit is led out between two adjacent switches, that is, three circuit breakers are used for two circuits, and the middle switch is used as * * *, which is equivalent to 1.5 circuit breakers for each element, so it is also called one and a half circuit breakers for wiring. In a half-connected string, two switches (such as 50 1 1 and 50 13) connected to the bus are called edge switches, and the middle switch (such as 50 12) is called intermediate switch or contact switch.
One and a half switch connections shown in the figure are "complete strings". However, due to the small initial scale, many expansions and large final scale of the 500 kV substation, there is often a "half-series" transition process, that is, only two bus switches in the 1 series supply 1 line at the same time, and the equipment naming number is changed accordingly in view of the long-term consideration.
At this time, although it is not strictly a half-switch supply 1 line, it still has the advantages of reliability and flexibility of a half-switch connection, and it is still called a form of a half-switch connection.