overhead line capacity
overhead line capacity
(OP)
Currently we are working on a overhead line project. The client specification limits the maximum delivered load for 34.5KV below 40MVA. I am trying to understand the reason behind it. We could use multiple conductor per phase at 34.5KV to increase the overline capacity similar to cables. But our client insists on changing to 72.5KV level, which would cause a lot of design changes. Any suggestions?






RE: overhead line capacity
Reactance may be a significant portion of the impedance. Parallel conductors will lower the resistance but not the reactance unless a second line is constructed.
Bill
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"Why not the best?"
Jimmy Carter
RE: overhead line capacity
RE: overhead line capacity
There's probably a good reason behind a 40MVA limit even if it isn't readily apparent.
RE: overhead line capacity
However, if their specification limits it to 40MVA and they as client are insisting on using 72.5kV it doesn't really matter what the reason is, if you want the job.
Regards
Marmite
RE: overhead line capacity
RE: overhead line capacity
RE: overhead line capacity
RE: overhead line capacity
RE: overhead line capacity
This standardization permits the use of readily available components like reclosers which typically have 600 A limits. On the distribution side of things, equipment is used in such high volumes that standardization offers great economies.
If you design it more like a transmission line, then you're more likely to customize it. In this case, you can consider 72 kV or 115 kV.
We have quite a bit of 35 kV distribution. On only a handful of situations have we paralleled conductors for higher capacity.
One drawback of introducing 72 kV - if you don't have any other 72 kV on your sytem - you pay a price for the complement of spare equipment. Of course, if you have other 72 kV stations, it's not an issue.
RE: overhead line capacity
What size wire are you putting in parallel? 670A doesn't seem like a particularly high ampacity, easily reached with 556 MCM conductor. Do you already have hardware in mind? Although parallel conductors at above 200 kV is common, I have not run across overhead distribution class equipment designed for it before.
RE: overhead line capacity
The availability of the autorecloser is another issue. This might be the reason our client specified 40MVA as 35KV Overhead line limit.