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Hi I'm Tobin Booth. This is Tech Talk Tuesday. Today we re here to talk about
this sample underground aluminum conductor and what you're looking at here are two current
carrying conductors, an insulated ground with a protective overcoating inside a metallic
armor and a protective overcoating, and this entire assembly is what we use commonly for
direct burial underground conductors on large scale solar array fields. The number one reason
we use an assembly like this is for cost savings. The aluminum underground conductors like this
are about a third of the cost of their copper equivalent, and every decision we make generally
comes back to that cost savings and why we use this specific conductor. Now in size versus
weight, yes, aluminum conductors are larger than their copper equivalents. However, the
weight is about half, so this entire assembly is about half the weight of a copper equivalent,
if a copper equivalent were to be used in lieu of this aluminum alternative. Now when
we go and cut a trench out in an open array field and lay this assembly in. we lay this
in as a single conductor, as a single assembly unit, instead of potentially gluing together
underground conduit, then pulling various sized cables through. This is laid down in
one complete assembly, and there is an amazing amount of time savings represented in that
simplified process. Now, let's look at the other end of this conductor. As you can see
here, we've stripped away the insulation and you can see the bare aluminum conductors being
exposed, the same with the ground. There is a reason that the ground is insulated and
I want to talk about that now. If the ground is going to be terminated within 18 inches
or less of the surface of the soil, the ground is required by the National Electric Code
to be insulated, and the reason for that is because condensation can occur between the
termination point and the ground creating corrosion and reduced electrical safety from
the ground. So, the ground is insulated and that's very important. You don't necessarily
see that if you were to pull a copper underground conductor, so that's extremely important for
choosing the proper aluminum assembly for underground applications. This is the conduit
body that's used to properly seal and terminate this assembly to a combiner box or other enclosure.
So, when you come out of the ground and into a combiner box, this is the proper assembly
to use. This conduit body seals against water intrusion, rodent, dirt, dust intrusion and
it provides the proper grounding point for protecting this assembly. And finally, let's
talk about terminations. We did mention that the ground has to be insulated for using an
aluminum conductor. That's essentially the message I wanted to convey here. Terminations
are extremely important when you're using an aluminum conductor and it s simply because
the thermal coefficient of expansion for aluminum is about double or more of its copper equivalent
and that thermal expansion over time can cause fasteners to loosen. So you have to use the
proper terminations to terminate this conductor, and you have to have a rigorous operations
and maintenance schedule to maintain this conductor and the electrical system over time.
These are the three major points that we consider when using underground aluminum conductors.
Hope this was useful to you. We'll look forward to seeing you next time. h+m+ gd+m+ hxkY h+m+
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