Cable Problem

This has been asked a bizillion times before.

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The voltage rating is the same as the wall thickness of the pipe. It does not tell you exactly how much fluid you can pass through the pipe, its more like the pressure rating.

In order to know how useful your pipe is you would need to look at the flow area. For a cable you would most likely have to see how much current you can pass through.

Try the formula for electric power = Amperage times Volts.

Ampere rating of electric conductors is determined by the following:

1. Composition of metal that conductor is made from. (Copper? Aluminum? Alloy?)

2. Configuration of conductor(s). (Stranded? solid?) (If stranded, how many strands?)

3. Ambient environment that conductor is used in.

4. Conditions/method of installation. (In free air? Bundled in free air? In metal conduit?)

5. Insulation type and temperature rating.

Only the Original Equipment Manufacturer cable/wire manufacturer can provide the correct ampere rating of a conductor, wire, or cable.

The cable should be stamped with voltage rating, conductor size, type of conductors (stranded or solid), number of strands, manufacturer's name, temperature rating, and quantity of conductors or with the manufacturer's code number.

If the cable does not have the above mentioned information details then you must find the manufacturer code identification number and contact the manufacturer to identify the needed information.

Once you determine the ampere rating of the cable/wire you must also determine the ampere rating reduction based on the ambient conditions at the installation site and type of installation method.

Apply the formulae required to find power handling capacity

P = EI (Watts) or (P = E x I x PF x 1.73 for 3 phase applications.)

6. Length of conductor.

By the way, the √3 (1.73) term in the above equation represents the 6.6/11 kV rating.

If <...we...> knew what <...we...> were doing, then <...we...> wouldn't need to ask in an anonymous global engineering forum!

Stop work and hire a professional.

The insulation determines the voltage. The amount of copper inside determines the current. Power = volts times amps.

I thought this might have become an interesting topic.

We once used a length of wire as a fusible link during HV DC transformer testing. We had a mechanical engineer determine time to melt given I^2 R losses.

in addiction with all the above you may want to consider a factor of security, that may help to use the installation in the future with a predictable increase of electrical loads.

It depends on the installation and/or the project...

Ask your electrician!

The voltage rating of a cable is not what determines the power capability. Since you don't know that, you are in the wrong kind of work. Try opening a massage parlor.

You'reeee welcomeeee

In my opinion, in order to chose the right cable you need more data than presented above-I am afraid.

First of all one has to state the required rated voltage.

The supply system rated voltage and frequency depends on local regulation. It is different from North America and from Europe, for instance. It has to be different if the system is grounded or not and it depends the ground fault clearing time, also.

Second one has to state the required the maximum current carrying capacity-ampacity-on the entire length of the cable-from terminal to terminal.

This depends on a lot of data: conductor material, cross section area and diameter, insulation type -usual PVC,EPR and XLPE- the way of laying, for instance: in free air, in conduit[which kind] in air, underground and so on. Also, ambient temperature and terminal limited temperature are important factors. And other factors are involved. One may get standard support as NEC,CEC,IEC,VDE and other. Sometime the standard does not fit the requirement. In this case one has to calculate the ampacity following for instance Neher and McGrath method or IEC 60287.

The third factor-for low voltage mainly-it is the permissible voltage drop.

The fourth factor-not the least- it is the short-circuit withstand current. One has to calculate the presumable short-circuit current through the cable, chose the fault clearing time and check the conductor cross-section area.

All cable are design by the cable manufacture and the cable are manufactured according to the IEE Standard and other standard as required. The cable size and the maximum current carry capacity is already pre-recorded inside the Current Carrying Capacity Table and it is provided free by all the cable manufacture. Why do you want to waste your time doing all the calculation. Just refer to the table and you will get your answer from there.

Sorry Simon, but in my opinion, IEE Standard -if you mean the actually BS7671-in 1992, the IEE Wiring Regulations became British Standard BS 7671- it is not a standard for cable design or construction. British Standards-other than BS7671-are. They are many of standards for cable design as Underwriters' Laboratories [U.L.44,83,1072,1581 and other],IEC 60502-1 and 2, BS5467, 6004, 6007, 6622, 6724 and other, DIN/VDE 0276 part 603, and other and other.

None of these standards deals with ampacity, voltage drop or other useful data in order to chose a correct cable but how to build and test a certain cable.

This another engineering specialty-how to build a cable it is different from "how to run a cable". It is like "how to build an induction motor" from "how to use" it.

They are other standard as BS7671, NEC, NEMA, IEEE, CEC, VDE 100,101,298 and other where you may found for a "standard conditions" the ampacity.