The circuit under maintenance is transferred to the transfer bus. The circuit breaker to be maintained is now opened, isolated and removed for maintenance. The transfer bus is energized and the isolator nearest the transfer bus of the breaker to be maintained is closed. When a tie circuit breaker is present, circuit breaker maintenance is achieved by closing the tie breaker. Circuit protection will be disabled in this maintenance arrangement. When no Tie CB is present, for maintenance of a circuit breaker, the transfer bus is energized by closing the isolator switches to the transfer bus, then the circuit breaker to be maintained is opened and isolated on both sides. One or more circuit breakers may be used in this arrangement to make connections between the main and transfer bus. In this arrangement one or more busses is added to the single bus substation scheme. Reliability and availability of this system can be improved by expanding and sectionalizing the bus. Single bus configurations are not considered reliable systems and they should only be implemented in substations where high reliability is not required, such as large transmission yards. This configuration requires less installation area and it can be easily expanded. The single bus substation configuration is the simplest and least expensive of all configurations. Circuit protection is disabled in this case. A bypass switch across the breaker should be used for maintenance of the corresponding breaker. Maintenance of any circuit breaker requires shutdown of the corresponding circuit/line and maintenance of the bus requires a complete shutdown of the bus. Failure of a single circuit breaker will also result in an outage of the entire bus. A fault on the bus or between the bus and circuit breaker will result in an outage of the entire bus or substation. There are six common substation bus schemes that every test technician should understand:Īs the name implies, the sigle bus substation configuration consists of all circuits connected to a main bus. A total shutdown of the substation means complete shutdown of all the lines connected to the substation.Ĭlearly, a EHV or UHV transmission substation where a large number of critical lines terminate is extremely important, and the substation should be designed to avoid total failure and interruption of minimum numbers of circuits. The first requirement of any substation design is to avoid a total shutdown of the substation for the purpose of maintenance, or due to fault somewhere out on the line. The operational flexibility and reliability of the substation greatly depends upon the bus scheme. In many large transmission substations, the total numbers of lines terminating exceeds one or two dozen.Ī substation bus scheme is the arrangement of overhead bus bar and associated switching equipment (circuit breakers and isolators) in a substation.

In actuality, most EHV and HV substations can be the point where more than half a dozen of lines terminate.

The electrical substation is a junction point where two or more transmission lines terminate. A substation bus scheme is the arrangement of overhead bus bar and associated switching equipment.

Substation optical isolator