cable size calculation for different voltage level

Vdrop = Current X Distance(Ft) X 2 X Ohms per 1000Ft for (60hz supply)

Many electricians wire for no more than 5% voltage drop

refer to this link: http://www.powerstream.com/Wire_Size.htm for a table for general design rules.

You calculate the electrical load and then determine the amperage depending on the voltage. You then look in a reference manual, such as the NEC, and get the cable size based on the amperage.

Hi Guest,

Apparently your question look very simple but the real technical answer needs lot more data and information .

There is no fixed formula to calculate the cable size. The calculation of cable will depend on many factors

1. Voltage of the system

2 .The source of supply

3. Distance of load centre from the source.

4. Ambient Temperature

5. Type of cable

6 Cable laying method

Other considerations are given below.

1. Short circuit rating of cable to be chosen

It will depend on power source, transformer capacity ,cable size ,insulation,initial temperature,finial permissible rise of temperature of the cable ( The data will normally be provided by the cable manufacturer)It will also depend on the type of cable PILC/PVC/ XLPE , Earthed or un earthed system etc. Duration of short circuit depending on the protective system and back up protection which are other important point to be considered

2.. Voltage drop

You must check the likely voltage drop for which standard chart is available which should be referred.

3. Power loss.

Power transmission loss in cable should be calculated as per the data provided by the the cable manufacturer.

4. Type of cable laying / depth of cable laying soil conditions etc. and other de rating factors to be considered for the calculation.

After considering the de rating factors and factor of safety you can arrive at the final calculation.