How to choose between single-bus and double-bus substations

A busbar refers to a multi-circuit common conductor in a power supply system; it serves as the conductor through which electricity enters and exits the system. Typically, copper bars are used to connect various switchgear units together in a row. A single-busbar system means that all incoming and outgoing circuits converge on one busbar. In the single-busbar sectionalization configuration, two power sources feed electricity into sections 1 and 2, which are connected to each other via bus couplers. A double-busbar system allows all incoming and outgoing circuits to converge on two separate busbars, offering a more complex yet flexible power supply arrangement compared to a single-busbar system.

1) Single-bus wiring: Single-bus wiring has advantages such as simplicity and clarity, fewer devices, lower investment, easier operation, and suitability for expansion, but it lacks reliability and flexibility. When a busbar or its isolating switch fails or is under maintenance, all power to the busbar must be disconnected. 2) Double-bus wiring: Double-bus wiring offers advantages such as reliable power supply, easy maintenance, flexible operation, and ease of expansion. However, this type of wiring requires many devices (especially isolating switches), resulting in complex distribution systems with poor economic efficiency. During operation, the isolating switches, acting as control devices, are prone to misoperation, which makes automation difficult to achieve. Especially when there is a fault in the busbar system, it is necessary to disconnect a large number of power sources and circuits for a short period of time, which is not acceptable in large power plants and substations that are of particular importance. 3) Bus with bypass: It offers high power supply reliability and flexible operation, but the investment is higher and its economic efficiency is slightly lower. Especially when using a bypass circuit breaker to take over, the operation is complex, increasing the chances of errors. At the same time, the installation of bypass circuit breakers complicates the corresponding protection and automation systems. 4) 3/2 and 4/3 wiring: Provide high power supply reliability and operational flexibility. Whether there is a bus fault or maintenance work, power supply will not be interrupted; except in the case of a fault in the tie circuit breaker, which causes short-term interruption of power to the two circuits connected to it, no other circuit breaker fault or maintenance work will disrupt the power supply. Even in extreme situations where both bus sets fail (or one set is under maintenance while the other fails), power delivery can still continue. However, this wiring configuration requires a large number of devices, especially circuit breakers and current transformers, resulting in high investment costs; both the primary control wiring and the relay protection systems are quite complex. 5) Busbar–transformer–generator set unit wiring: It features simple wiring, fewer switching devices, easy operation, suitability for expansion, and reduced short-circuit current on the low-voltage sides of the generator and main transformer, as there is no busbar for the generator’s output voltage.