Friday, May 17, 2013

Exothermic welding: Cable to cable connections

Just a few pictures today … on exothermic welding joint of earthing copper cables.

Picture 1: Cable-and-mould set-up for a cable-to-cable exothermic joint
(Click on the picture to enlarge it.)

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The above picture shows the set up for a cable to cable connection.
For the uninitiated, I have labeled the components in Picture 01 and show them again in Picture 02 below.

Picture 02: Exothermic welding process set-up labeled
(Click on the picture to enlarge it.)

I will not write much today and I have serious doubt that I will be able to write long posts again in the near future.

The best I can do is to show you some pictures. When I have more time I will write longer.

Note that the part that I labeled “explosive powder” is not really explosive powder. Well, It IS explosive, but it is not an EXPLOSIVE.

It is actually some powdered mixture of copper oxide and aluminium. When ignited, the mixture produces a very high temperature reaction that molten the copper and aluminium components which then flow into whatever cavities between the conductors to be joined, as well as form a thick layer of alloy envelope around them.

This you can see in Picture 07 below.

Picture 03: Just a closer view of the mould.
(Click on the picture to enlarge it.)

Picture 04: A shot during the combustion
(Click on the picture to enlarge it.)

Picture 05: A cable-to-cable joint still red-hot
(Click on the picture to enlarge it.)

For the curious, the earthing cable conductors in the pictures are 95 mm.sq stranded copper cables.
This installation was part of an earth mat type earthing system. High voltage substations for voltages 33kV and above usually have some sort of “step voltage” protection and the earth mat or earth grid is part of the “step voltage protection system”.

For beginners who have no idea at all of what all this means, have no worry. I will send a post or two on “earth mat” and “step voltage“ soon.

Picture 06: A completed cable-to-cable joint
(Click on the picture to enlarge it.)

Picture 07: A closer view of the finished exothermin joint.
(Click on the picture to enlarge it.)

Okay, folks. See you in the next post.

Jimmy Lee Wan Seng
(Information Trader)

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