Electrical Substation Equipment: Bus Bar and Its Functions

In a substation, a bus bar refers to a metal bar or a system of bars used to conduct and distribute electrical power within the facility. It serves as a central point for connecting and interconnecting various electrical components and devices, such as circuit breakers, transformers, disconnect switches, and other equipment present in the substation.

Why are Bus Bars Used in Electrical Substations?

Fig-Typical Bus Bar System

The primary purpose of a bus bar in a substation is to efficiently transfer and distribute electrical power between different parts of the substation and the power grid. It acts as a common electrical connection point, allowing for the smooth and safe transfer of electricity at various voltage levels.

Copper and Aluminum Bus-bar Size Selection Chart

What is Bus-bar?

Bus-bar is the common header where one or multiple sources poor the power also one or more sources can take power simultaneously; means bus-bar is a common bus that receives power and releases power.

Literally, the bus bar is usually a very thick wire or bar that leads from the power source and is the wire that every load in the system is connected to.

Bus-bar is like a city water reserver where water is accumulated and distributed from.

Types of Bus bar

Bus bar mainly classified into two, though the function is same.
1. In outdoor substation the bus bar is a kind of bulk-sized aluminium conductor;
2. In indoor substation copper or Aluminum bar is used as a bus bar.

Why Bus bar is required in an electrical transmission network?

In electrical substations, the bus bar is a common component where all the anchorages that have the same voltage level are connected. In an electrical transmission network, it’s required an electrical node but it is physically impossible to connect all the bays- such as transmission lines, transformers, reactors, shunt capacitors, etc. into a single point. But, the bus-bar system provides the best solution that can connect all equipment together and this node is known as the bus-bar system.

Typical Sectionalized Double Bus bar Arrangement System

The figure shows a typical substation with two main bus-bar with a bus-coupler connection facility, also shows auxiliary bu-bar and outgoing feeder connection with isolator and circuit breakers. Different configurations in substations and multiple bus bars are used to assure a constant operation even if a circuit breaker or any other element requires maintenance.

Copper Bus-bar Selection Chart

Electricity is usually sent over electrically conductive metal wires. The wire is more convenient because we can put insulation on it and bend it around corners, move it around, string it between power poles, that sort of thing. But, sometimes wire isn’t the best option, it may be easier if we used a solid conductor instead of wire which is bus-bar. The chart below shows a copper bus-bar selection procedure.

Aluminum Bus-bar Selection Chart

Using slabs of metal instead of the cable has some advantages- we can bolt them into place using insulators, and just like a welding table, we can attach a connector anywhere on the bus bar. The chart below shows the Aluminum bus-bar selection procedure.

What are the Advantages of Bus-bar Trunking over Cabling System?

1. Bus-bar trunking save the cost compared to a cabling system
2. Bus-bar trunking reduce installation times on site compared to hard-wired systems.
3. Bus-bar trunking provides increased flexibility in design for future modifications.
4. Greater safety and peace of mind for specifiers, contractors and end-users.
5. Bus-bar trunking is easy to design/estimate and the installation stage is also cost-effective.
6. Distribution bus bar distributes power along its length through tap-off points along the bus bar, tap-off units are plugged in along the length of the bus bar to supply a load that could be a sub-distribution board what reducing production downtime.
7. Installed vertically the same systems can be used for rising-mains applications.
8. Certified fire barriers are available at points where the bus bar passes through a floor slab.
9. Very compact so provides space savings.
10. Protection devices such as fuses, switch fuses or circuit breakers are located along the bus bar run, reducing the need for large distribution boards and cables running to and from installed equipment.
11. Bus bar trunking can be installed with a natural galvanized, aluminium, or painted finish.
12. Special colours to match switchboards or a specific colour scheme are also available on request.
13. Uneven distribution of current takes place where multiple runs of cables are used in parallel.