What kind of cable is this?

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sb1975

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I don't know if this is the right forum to ask this but if someone knows they would be on this site.

I know what kind of cable it is but I wanted to know more about it... the poco left it behind when running it down the street. Could someone tell me what the 10 outside copper wires are used for? I asked the guy at work be he had no clue.

hope this works... if not try http://tinypic.com/view.php?pic=2u6lac8&s=3
2u6lac8.jpg


Thanks a lot!
 
Looks like a 15Kv #2 AL solid dialectic medium voltage cable with concentric neutral. The ten copper conductors are the neutral. For that size conductor, 14 AWG. This means that this cables has a full size neutral. Depending on how it was installed, ampacity can range from 175 to 130
 
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Would this be considered medium voltage cable?

I've seen a sample of the "high voltage" stuff and it has a lot more layers than that cable does.
 
Its high voltage. The type of cable used depends on the voltage rating. I have seen 69Kv wire with a 1500kcmil cu conductor, that it shield. It also included the concentric copper wire that is bonded to the shield wires.
 
72.5kv said:
Its high voltage. The type of cable used depends on the voltage rating. I have seen 69Kv wire with a 1500kcmil cu conductor, that it shield. It also included the concentric copper wire that is bonded to the shield wires.
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Per IEEE, medium voltage power didtribution equipment is rated from >600V to 69,000V. So this is a Medium Voltage cable.
 
sb1975 said:
I don't know if this is the right forum to ask this but if someone knows they would be on this site.

I know what kind of cable it is but I wanted to know more about it... the poco left it behind when running it down the street. Could someone tell me what the 10 outside copper wires are used for? I asked the guy at work be he had no clue.

hope this works... if not try http://tinypic.com/view.php?pic=2u6lac8&s=3
2u6lac8.jpg


Thanks a lot!
Click to expand...
This is a primary feeder cable probably 13kv or so the conductors on the outside is the neutral imbedded in some sort of semiconductor creating an equipotential shield around the outside surface of the cable thereby eliminating any uneven stress to the insulation material. The insulating material is probably some sort of crosslinked poly down to a semiconductor surrounding the center conductor. Looks like a #2 al.
 
zog said:
Per IEEE, medium voltage power distribution equipment is rated from >600V to 69,000V. So this is a Medium Voltage cable.
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Has that changed? The information I have is:

LV = Voltage levels that are less than or equal to 1 kV

MV = Voltage levels that are greater than 1 kV, but less than or equal to 69 kV

HV = Voltage levels that are greater than 69 kV, but less than or equal to 230 kV

EHV = Voltage levels that are greater than 230 kV, but less than or equal to 800 kV

UHV = Voltage levels that are greater than 800 kV

I agree that this is probably medium voltage cable. I would guess that it is #2 Al. 15 kV GRD Y XLPE (it has a translucent look to it) with either a full or 1/3 size concentric neutral and a PE jacket. :D
 
Is this cable rated for direct burial?

Our local utilities don't use directly buried MV cables here (always conduit or duct banks) However, I'm aware that direct burial is common in other parts of the country.
 
peter d said:
Is this cable rated for direct burial?
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I don't know of any that is not for direct burial. Also, most of the cable we install is direct buried except under paved areas. We don't use listed cable if that is what you meant by rated. :smile:
 
Doing privately owned sub-station change outs for large pharmaceutical plants 12Kv. I've always wondered what those outer copper strands were for. I would have never have guessed it was a neutral.I'm glad you found that wire and posted.Otherwise, I'd still be in the dark as to what those outer copper strands were for.:grin:
 
You can estimate the voltage level of that cable by measuring the thickness of the insulation. 200 MILS for 15 kV, 260 MILS for 25 kV (if I remember correctly) or thereabouts depending if it's 100% of 133% insulation. All of the insulation thickness is standardized based on the dielectric strength of the material versus voltage level. So that's why it's always the same.

Also, as Charlie mentioned, you can differentiate between XLPE (cross linked polyethylene) and EPR (ethylene proplyene rubber) by the color of the insulation. XLPE exhibits that semi-transluscent color while EPR looks more like standard orangish rubber. EPR can reach higher temperatures at the cost of greater dielectric losses, while XLPE exhibits less dielectric losses, but is typically rated 15 C less than EPR (which means lower ampacities). Like everything else, the differences are a trade-off: lower line losses versus higher ampacities.

The concentrics, if they're solidly bonded (i.e., grounded at multiple locations, which they typically are), will carry neutrals currents for the cable system.

Higher voltage, solid dielectric cables with concentrics (i.e., greater than 69 kV), however, will almost never solidly ground those neutrals due to the loss in ampacity. Most high voltage cable installations will either single point bond or cross bond those neutrals to eliminate the induced current on those neutrals, which in turn significantly increases ampacity.

If you've ever seen a high voltage, solid dielectric cable installation and notice the neutrals on one end are connected to a voltage arrestor at the riser, you'll know the system is single point bonded and for very good reason since you can lose 20% or more ampacity simply because of the induced current on the neutrals. Also, most high voltage solid dielectric cables (greater than 69 kV) are almost ALWAYS XLPE or PAPER/OIL/PIPE TYPE (even though EPR is rated higher in temperature) simply because of high dielectric losses of EPR.

EDIT: sorry, the bulk of existing high voltage UG cable installations are pipe type, high pressure, paper insulation, oil filled cables (HPOF), but a lot of the newer installations are solid dielectric (XLPE) because it's cheaper and performs comperably.
 
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Thanks everyone, yea I knew it was a high-voltage cable but was unsure what the outer conductors were used for.
 
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