River Crossing with PV Power Cable

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Jim Nolan

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Location
Oregon
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Telecom Engineer
I have a project where I have a 260 ft River crossing using an 1/2" galvanized aircraft messenger cable with minimum breaking strength of 24,000 LBS.

The messenger will carry 8 conductors. Each conductor will be #8 AWG Stranded CU with RRH insulation. Three Aircraft Hazard Balls will be attached to the cable.

I have asked several Cable manuglfacurers to fabricate this composite Cable and deliver 300-ft of it on a single cable reel.

However, they have responded with up to 18 weeks delivery time. Which is loner than I want to wait.

If I order the cables and messenger seperately and wrap the cables around the messenger wire myself, I can get the wire much sooner.

The problem is I am not sure if I can do a proper job of wrapping eight #8 stranded conductors around the single messenger wire by hand.

I thought, perhaps, to stretch the messenger cable between two vehicles and then, one by one, wrap each 300-foot run by hand individually. I am just not sure if I can get all eight conductors to lay down correctly onto the messenger cable surface in an even spacing.

Also I would need to know the correct number of feet per turn I should use.

Does anyone have experience wrapping this many conductors onto a single messenger? Is thwre a wire spooler out there I can purchase that can do the job?
 
IMO, wait and let them do it so liability doesn't fall on you. That is a long distance to have to have to wrap around a messenger. Perhaps there are fittings that attach to the cable and no wrapping involved
 
Seems to me I have seen cables secured to a messenger wire with some kind of doohickeys that clamp on every few feet. No twisting required.
 
petersonra said:
Seems to me I have seen cables secured to a messenger wire with some kind of doohickeys that clamp on every few feet. No twisting required.
Click to expand...
I have seen CATV/ISP cables supported this way as well.
 
OP, please come back with a photo of the install across the river...would love to see.
 
Why aren't you boring this application? Why isn't the Army Corp of Engineers involved?
This seems so dangerous!
 
Oh and like no client has never left you hanging with a bag of problems, last minute that the owner or GC didn't
just dump on your position. OH I thought you had that . . . Your the engineer. I have several professional friends and I've
heard a boat load of them.

I totally understand exactly what you're saying don't get me wrong. Far be it me to question the obvious.
 
There is stuff like this

www.techtoolsupply.com

HellermannTyton Aerial Support Plastic Spacer - 12.4in - 500 pieces

The PA66HIRHSUV Aerial Support Ties from HellermannTyton feature a built-in spacer to separate cables from the support wire and prevent abrasion. A one-piece design, combining the tie and spacer into one part, reduces installation time and inventory costs. The outside serrations along the strap...
www.techtoolsupply.com

However I've always been concerned about longevity with zip tie type products.

I agree a lasher is the way to go, however they are quite expensive maybe you can find someone who rents one or will do that step for you.
 
Jim Nolan said:
I have a project where I have a 260 ft River crossing using an 1/2" galvanized aircraft messenger cable with minimum breaking strength of 24,000 LBS.

The messenger will carry 8 conductors. Each conductor will be #8 AWG Stranded CU with RRH insulation. Three Aircraft Hazard Balls will be attached to the cable.

I have asked several Cable manuglfacurers to fabricate this composite Cable and deliver 300-ft of it on a single cable reel.

However, they have responded with up to 18 weeks delivery time. Which is loner than I want to wait.

If I order the cables and messenger seperately and wrap the cables around the messenger wire myself, I can get the wire much sooner.

The problem is I am not sure if I can do a proper job of wrapping eight #8 stranded conductors around the single messenger wire by hand.

I thought, perhaps, to stretch the messenger cable between two vehicles and then, one by one, wrap each 300-foot run by hand individually. I am just not sure if I can get all eight conductors to lay down correctly onto the messenger cable surface in an even spacing.

Also I would need to know the correct number of feet per turn I should use.

Does anyone have experience wrapping this many conductors onto a single messenger? Is thwre a wire spooler out there I can purchase that can do the job?
Click to expand...

First off I’ve never heard of RRH. I’m guessing you mean RHH/RHW? RHH is for dry locations only. And on messenger wire everything must be sunlight resistant too. That’s asking a lot. Have you seen old RHW outdoors over time? Plus 24,000 pound strength at 1/2” is way above conventional IWRC alloys. Good luck finding that stuff if you ever need to replace. Have you seen how badly galvanized aircraft cable rusts in a high humidity environment? I’d go with something a lot more conventional.

At 300 feet I’m actually shocked a cable manufacturer will even talk to you. Normally custom cable runs are at least 2000+ feet. This is because they have to set everything up and then run cable just for you. The markup must be sky high. They are more likely to make 5000 feet and charge you for it, then keep the rest and sell it. You are probably getting a consolidator quote.

It will weigh 0.068 x 8 x 300 = 163 pounds. Even including the cable itself you only need a few hundred pounds. I don’t understand why you would want to use an alloy like that. A common electrical grade high strength cable is ACSR. The steel strands are aluminum coated. It lasts 50-100 years or more, far longer than aircraft cable. Plus it has an ampacity rating so it can eliminate a ground. For a 300 foot span you’d maybe sag it 6 feet initially so the tension is nowhere near the rated strength. And I’d go maybe around 1:4”. 1/2” is a lot at that short of a span. The tension mostly determines the strength required anyway, not the weight.

As for attachment if you look at triplex up close it is not tightly wound. As it heats and cools it will stretch. You don’t want tightly wound. Just lay them all on the ground cinched to something at one end with tie wraps. Then bind them all together. For longevity you can use stainless steel tie wraps. Or you can go old school and wrap them with #6 soft drawn aluminum wire which bends easily by hand, Just tie it every 18 to 24 inches.

But I would not do it that way. Let’s say for a minute we have two 3 phase, 4 wire circuits or even two 3 phase circuits with 2 static lines. That gives us 8 conductors, same as needed. We can go with AAC or ACSR with the smallest sizes (#6). They will be open air single conductor so even though it’s aluminum there is no 70% derating for 8 current carrying conductors and we get single conductor ratings, easily exceeding the #8 RHW bundle. It will run cooler and voltage drop will be lower. As aluminum it is sunlight, ozone, and corrosion resistant. And local utility contractors are familiar with what you want to build and can do it quickly and inexpensively with readily available materials.
 
paulengr said:
First off I’ve never heard of RRH. I’m guessing you mean RHH/RHW? RHH is for dry locations only. And on messenger wire everything must be sunlight resistant too. That’s asking a lot. Have you seen old RHW outdoors over time?
Click to expand...
I assume he is talking about PV wire which is type RHW-2 and sun res.

paulengr said:
At 300 feet I’m actually shocked a cable manufacturer will even talk to you. Normally custom cable runs are at least 2000+ feet. This is because they have to set everything up and then run cable just for you. The markup must be sky high. They are more likely to make 5000 feet and charge you for it, then keep the rest and sell it. You are probably getting a consolidator quote.
Click to expand...
Actually getting conductors plexed is no problem in short lengths, I get it done frequently when i order in conductors such as colors Or want a custom URD assembly. That said, Im not sure how it would work with a nonstandard "conductor" that they certainly dont have like a wire rope.

paulengr said:
But I would not do it that way. Let’s say for a minute we have two 3 phase, 4 wire circuits or even two 3 phase circuits with 2 static lines. That gives us 8 conductors, same as needed. We can go with AAC or ACSR with the smallest sizes (#6). They will be open air single conductor so even though it’s aluminum there is no 70% derating for 8 current carrying conductors and we get single conductor ratings, easily exceeding the #8 RHW bundle. It will run cooler and voltage drop will be lower. As aluminum it is sunlight, ozone, and corrosion resistant. And local utility contractors are familiar with what you want to build and can do it quickly and inexpensively with readily available materials.
Click to expand...

I kinda like the idea of using bare AAC or ACSR. Pretty easy really if you just can get the spacing and tension figures.
 
jaggedben said:
Is there a good reason you can't combine the four circuits into one so that you can use a off-the-shelf messenger cable product?
Click to expand...
I am assuming he is running 1kv DC strings, but more info would certainly help. If that is the case, perhaps dropping to 600 volt would be worth it. If combining is not prudent, could just run four runs of standard triplex. Not sure off hand of maximum spans for standard messenger cable, I'm sure there are charts available.
 
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