Electricity is complex system and in order to understand it, you will have to break it down into subsystems and farther into components. In our discussion today, we will look at busbars. A busbar is a metallic strip or bar that is a good conductor of electricity that ‘transports’ power from incoming feeders to distribution feeders. To carries incoming power and distributes to all connected outgoing conductors.
The main function of bus busbars is to conduct electricity from incomer feeder lines to output feeder lines. Essentially it is a conductor doing the same work the cables do. They are made of copper, aluminum or brass as they have high electrical conductivity. They are fitted in switch gear units allowing incoming power to be distributed to several outgoing circuits. The bar forms the connection point of inputs and outputs. Usually they are not insulated with polymer materials meaning when they touch each other they are electrically connected forming a short circuit. They are installed on the mounting panel board to be firmly held in place using insulators. Positioning is done in such a way to provide enough clearance from one another. The bars may be painted with a given colour code to mark what they are carrying i.e. Phase, neutral or earth just like in cables.
Shape and Arrangement
The most common shape is a rectangular strip, other shapes are round and hollow tubes. Rectangular strip is preferred because it has high conductivity as the skinning factor is low. The high surface area to volume ratio also makes cooling effective. Hollow busbars are preferred to solid ones as they have high conductivity, low skinning factor, less bulky and high cooling rates. The arrangement highly depends on number of incomers, outgoing circuits and switching operation desired. The commonly used types include;
- Single busbar – one unit is used to connect input and output
- Sectionalized busbar- divided into sections which can be closed or opened using disconnectors and circuit breakers
- Main and transfer busbar- two busbars with a coupler that can close or open them
- Double busbar- two units not coupled being connected to output lines, the line have circuit breakers and can take power from either busbar.
- Sectionalized double busbar- integrates the operation of sectionalized and double busbar
- One and a half breaker busbar- has two bars and three circuit breakers for output line, any of the breaker can supply power to outgoing conductor.
- Ring busbar- bars connected to form a ring using switched couplers
- Mesh busbar- connections forms a mesh like shape where breaker switching allows power from one source be directed to desired output.
- It’s easy and fast to install, additional circuit supply or draw power by tapping from the busbar.
- Low facility cost- no expensive cabling required both at initial or future expansion. Busbar are cheap compared to equivalent size cables.
- They are secure, reliable and better cooling- lack of insulated makes them efficiently to be air cooled. They are durable, faulty easily detected and easy to service.
- They are environmental friendly- hollow conductor are light, no need of strong support structures. Since they don’t have polymer insulators, they are fire resistant.
Busbar used for?
- Power distribution stations- bulky high voltage power from transmission line is stepped by power transformers then fed to busbars where many distribution circuits are powered from. They tap from common bar.
- Building power connection- where cables are expensive and bulky to install, busbars becomes the best alternative. Rising busbars are used in storey houses.
- Design and construction of distribution board and consumer units.
Engineering provides solutions to world problems. A busbar may look a simple component and a passive one but power distribution system really respect it. Did you know your office or home consumer unit has a busbar? A word of caution; Never ever touch a busbar, remember we said it’s not insulated. For a technician always switch make sure you have disconnected the bar by switching off incoming and outgoing lines. Equally important, ensure you have earthed the bar (after disconnection) to drain static charges.
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