Sunday, April 10, 2011

Switchboard earthing busbar

This post shows some pictures of the earthing busbar of a main switchboard. Click here to go back to the main post, Switchboard electrical earthing.
Photo 1 - View of the lower part of a main switchboard
You may be wondering why I did not stand back a little bit and take a wider view of the subswitchboard. The would give a nicer picture, right?
I however took this picture when the main switchboard (MSB) has already been located on its actual position in the electrical switchroom (LV Switchroom).
Usually the layout of an electrical LV room is such that the main switchboard is located near the wall of the room. The space behind the board is usually between 600mm to 1000mm between the back of the switchboard and the wall.
In fact 750mm is a more common space clearance for office and residential building. This of from my own personal experience. I do see projects where the architects were more generous.
In those cases you may then find that the clearance is between 1000mm to 1300mm.
Okey, back to the earthing busbar.
Here you see that the switchboard earthing busbar is located at the near bottom towards the rear door of the switchboard. This is a common practise.
The phase busbars are usually at the top part of the 2 meter plus main switchboard.
Here you may also notice the the photo shot was taken at the left end of the long switchboard. "Left" if you look at it from the rear.
So here you can also see how the busbar is mounter to frame or the chasis of the board. This is not how the phase busbars are fixed in place.
You can see the pictures of how they are fixed in future posts. Maybe if you browse around this blog, you may be able to see it already but I cannot be very sure if I have already uploaded a photo that contain this information.
Photo 2 - The earthing busbar of the switchboard
I just zoom in a little onto the busbar so you can see the details better.
Notice how the end of the busbar is fixed to the switchboard structureal frame. This way the structure is automaticalled earthed.
Notice also the green color sticker located on the busbar approximately at the middle of the panel opening.
Photo 3 - The green/yellow submain earthing cables and copper tape
The function of the switchboard earthing busbar is not only to ground the equipment and metal parts loacted on the switchboard.
It also serves as the feeder the grounding facilities that are needed by submain circuits taking supply from the particular main switchboards or cubswitchboard.
So in the above photo you can see four earthing connections: three from grounding cables with green/yellow insulation, and one from a 3mm by 25mm copper tape.
Each of these grounding conductor would be running along its respective phase and neutral conductors.
Photo 4 - The earthing connection to switchboard rear door (metal parts)
The specifications in the original article, Switchboard earthing, requires that all doors of the switchboard be properly connected to the grounding busbar.
So here is how it is done.
Note that it is a common practise to use spring washers to secure the cable ends to the bolt and nut.
It should be noted also that the cable lug should be a ring type.
A fork type of cable lugs should not be accepted.
Photo 5 - Branch earthing connections to the earthing busbar
When the specifications say branch earthing connections, this is what it meant.
The insulated green wires terminated to the switchboard earthing busbar is the earthing branch connections.
The provide proper and reliable connection to all live equipment and components on the panel or inside the switchboard.
Click here to go back to the previous post, Switchboard earthing.
Note: This anchor post, Free electric installation pictures , may contain a summary of the materials you are looking for. It can be faster than clicking through each post title at the Blog Archive. I started it long ago but never actually got around to finish it.
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row anco said...

It’s actually a great and helpful piece of info. your article let me know a lot of things.thanks for sharing main switchboards

row anco said...

This is a very nice blog and thanks for sharing the information
main switchboards