# What is (roughly) the ratio of insulation-to-conductor cost in a cable? [closed]

Somewhat related to this question on aluminum vs copper, when making a cable one needs to consider the cost of insulation as well. I suspect there may be significant variance depending on technology, rated voltage, rated temperature, rating for mechanical stresses, and so forth. Are there some rough estimates (even as ranges) of how much the insulation costs relative to the conductor cost?

I'd be perfectly happy with analysis on some commonly used cables, e.g. extension cords for household use (at one end) and, say, metropolitan underground power cables (at the other).

There's not much in the way of cost breakdown analyses for power cables that I could find. One presentation by General Cable briefly mentioned that "Purchases of raw materials account for 75% of total manufacturing costs for most manufacturers." So at least we know that the cost of materials is important in this sector...

## closed as too broad by Leon Heller, PeterJ, Sparky256, uint128_t, ThreePhaseEelDec 28 '17 at 12:39

Please edit the question to limit it to a specific problem with enough detail to identify an adequate answer. Avoid asking multiple distinct questions at once. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.

• Is there a reason you expect that ratio to be different than the retail prices? – PlasmaHH Dec 24 '17 at 12:44
• I'm voting to close this question as off-topic because it is nothing to do with electronic design. – Leon Heller Dec 24 '17 at 12:53
• @PlasmaHH: retail prices (of the readily assembled cables) have more hidden variables. You could surely try to reverse-engineer the cost ratio from the retail price(s) e.g. given two cables with the same conductor but different insulation, from (c+x) and (c+y) deterimine x/y, if you estimate c. Is this the best way? – Fizz Dec 24 '17 at 12:55
• @LeonHeller: It surely has a lot to do electrical engineering (cable) design. This site is not only about board/chip electronics. – Fizz Dec 24 '17 at 12:56
• It’s vague to only specify cost of insulation or conductors , when there is far more to the design of an underground HV cable that must withstand different mech/climatic stresses with semiconductor and water protection needed – Sunnyskyguy EE75 Dec 24 '17 at 15:48

Cross-sectional area will vary with square of diameter. Circumference will vary linearly.

So to answer the part related to Why aren’t the main conductors in this underground power cable made from copper?:

• Aluminum has 61 percent of the conductivity of copper. For the same resistance then we need $\frac {1}{0.61} = 1.64$ times the cross-sectional area.
• The diameter of the aluminium cable will be increased by $\sqrt {1.64} = 1.28$ times that of the copper conductor.

If the diameter of the cable is large relative to the thickness of the insulation that would give a 28% increase in insulation cost.

According to Plasticker.de PVC is about €0.40 per kg. (I'm not in the business so I don't know what quality or plasticisers are required for insulation.)

• Aluminium seems to be about €1.78 / kg. Infomine.
• Copper is about €5.80 / kg.

Given that underground (U/G) High Voltage (HV) distribution cable has earthed sheathing, moisture protection , rodent protection AND HV protection

Consider that the cost of U/G sheathed cable is greater than least expensive O/H cable implies that the difference is due to better insulation from many causes; Electrical, Climatic, Mechanical and Rodents who love to eat plastic insulation.

Electrical stress is far greater since the sheathing is earth or Neutral grounded to a 3 phase distribution with the separation gap which also lowers distribution impedance.

Climatic U/G cable stress is quite different from O/H. U/G in areas with frost must deal with more frequent condensation failures in spring. O/H in high temp climates must deal with UV exposure to jacket insulation if any and O/H exposure to lightning strikes can damage insulation to network

Although O/H is easier to fix, some studies in S. Korea suggest higher costs of U/G cable result in lower life cycle costs from lower frequency of insulation failures.

3 Phase and single phase U/G cable shown above. Note that only the relatively small center carries power to the load. The other conductors are for other purposes to protection the insulation from failure.

The most critical test of any U/G armored cable is the PDIV factory and field test results. These are TYPE or considered optional in theory, but essential in practice and not hard to do. It is the best offline wear test or using PD online monitors.

• Ok, the absolute insulation costs are no doubt higher than for joe's home extension cable. But does that translate into higher or lower relative costs of insulation vs conductor(s)? Because there is also more conductor material in an underground power cable. – Fizz Dec 24 '17 at 15:11
• If you markdown without justification , that is lame – Sunnyskyguy EE75 Dec 24 '17 at 15:43
• Eh, dunno who downvoted, but the info is somewhat useful, so I'm gonna compensate for the downvote... – Fizz Dec 24 '17 at 17:53
• TY Fizz.. good luck in your search for answers – Sunnyskyguy EE75 Dec 24 '17 at 19:56

A lot of the cost will be the amortization of the capital expenditure for the plastic extruder, capstans and winder required to apply the insulation. That would include the associated control and power distribution items. In addition to the equipment cost, you must consider the cost of the designing the installation. Also there is the balance of the associated manufacturing facility. You would also capitalize the shipment and installation expenses. Once the equipment is in operation, you would have the material, energy expenses, labor and overhead associated with insulating the wire. A small portion of that would be the material cost of raw insulation material. That would vary quite widely depending on the type of insulation.

The cost-wise breakdown doesn't seem easy to come by. It's somewhat easier to find a breakdown by weight... for networking cables. And that's because the EPA (which is interested in recycling these) has one.

Basically about 50% of a networking cable's weight is copper, the rest various plastics, which do vary substantially with the type of cable. The EPA has info for two types CMP (plenum) and CMR (riser) cables. For CMR they give the breakdown of non-copper materials as 37% PVC, 23% HDPE, 11% "Phthalate-based plasticizer". For CMR the information is not that precise; fluorinated ethylene propylene (FEP), PVC, aluminium trihydrate, and generic fluoropolymer account for ">5%" each. For both types of cables the whole bill of materials is pretty long (~20 items or so). I still think this info is somewhat useful as it shows the difference in materials between cables that are ran through walls and those that are not.

More to the point here, the same EPA document gives a table for NM-B power cables:

PVC dominates the jacket, at least in the non-Pb-free version. But unlike for networking cables, the weight of the copper is given very imprecisely for NM-B cables.

Reverse-engineering a cost estimate from a weight-based bill-of-materials like these is a bit of a tall order; some substances used in small quantities could be rather expensive, some of the info is rather imprecise, etc.