Electrical Busbar Classification, Management With Calculation

Busbar in Panel Board

We use a network of cable with different voltage rating to transfer electricity through the circuit. Copper and Aluminum are the most popular cable conductor. Same like Electrical Busbar is a modern way to transfer electricity by using Copper and Aluminum Plate which is covered by a protecting insulating cover or not. Generally, we drill a hole on Busbar and then we bolt cable lugs with it.

Usages of Busbar:

Busbar is frequently using inside a panel board and as the main power carrier from power transformer and generator. Now the reason behind the use of Busbar as follows,

  1. We can easily transfer electricity to a different load.
  2. If you are using Busbar then you can keep one side of bus bar active when you are performing maintenance to a load side.
  3. If there is any glitch in the system then you can deactivate that part from the active system.

The feature of Busbar:

  1. The conductor you use as a Busbar that must have less resistance value.
  2. If there is any change in temperature due to load demand then conductor material resistance value will not change.
  3. Required insulation material space between two or more conductor must be available.
  4. Busbar metal conductor should have high mechanical strength.
  5. If in near future, output load limit is increased then it should have the capacity to adjust with a required load to a specific limit.
  6. Future extension opting should be available.

Related: Electrical Isolator

Classification of Busbar:

Generally, Busbar classification depends on its usages like where to use it, load type and others. Here is some different type of Busbar,

  1. Outdoor Busbar.
  2. Indoor Busbar.
  3. Enclosed Busbar.
  4. Open Busbar.
  5. Isolated Phase Busbar.
  6. Gas-Pressurized Insulated Busbar.
  7. Oil Sinking Busbar.

Busbar Management:

Busbar management as follows,

  1. Single Busbar.
  2. Sectional Single Busbar.
  3. Sectional Double Busbar.
  4. Double Busbar with Single Breaker System.
  5. Ring Busbar.

Now come to the selection of a Busbar size. There are some rules and guidelines that need to maintain during designed or select a Busbar and those are,

  1. According to the plant efficiency, Busbar should have an opting to active entire Busbar or half of Busbar.
  2. Amount of load needs to carry.
  3. Primary installation cost.
  4. Operation and maintenance cost.
  5. Future extension option.
  6. Busbar size selection.
  7. A safe place to install.
Busbar in PFI Panel
Busbar in PFI Panel

Busbar Size Calculation:

Generally, a Busbar size depends on the total ampere of current that it needs to carry. If carrying current is small then its size will be small and if it is carrying a high amount of current then its size will be large. When you are calculating the size of a Busbar then you have to keep in mind its height and thickness of conductor plate that you use. Calculation of Busbar will denote by millimeter.

Example of Busbar Calculation: Let’s consider we have a 600KVA power transformer or a generator which have 400V as line voltage. Now total ampere we can get

I=(1000×600)/(√3×400)=866A

Now we have to add a minimum of 25% extra ampere for safety reason with 866A. You can add more percent according to your demand with future extension. Then our total ampere will be 1082A.

Now Basbar calculation formula is,

  • 2A=1mm ^ 1A=1/2mm^

1082A=541mm^

Please note that 2 (1.7~2) is the density of copper. If you go with 1.7 then 25% extra ampere will not be required. Now we have to reach 541mm^ by multiplying height and thickness of copper like 108×5=540A. If this size of copper plate is not available in the market then take the nearest size but upper size.

Related: General Question About Circuit Breaker

Some Common Busbar Size:

Here is some most common Busbar size,

19.05mm×6.35mm = 100A

25.40mm×6.50mm = 250A

30mm×10mm = 400A

40mm×10mm = 600A

44.45mm×12.70mm = 800A

50.80mm×12.70mm = 1000A

2×63.5mm×9.525mm = 1600A

2×80mm×10mm = 2500A

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