cable selection
cable selection
(OP)
Is any one know how volts per ampere per meter and current ratings calculated in different manufacturer brochure for any 4 phase unarmoured cable pvc insulated/pvc sheathed 30 degree ambient and 70 degree operating temperatures for cable 600/1000 volts for particular installation method e.g if 4*95 mm sq unarmoured burried in direct underground duct with trefoil etc how is calculated?






RE: cable selection
DIN VDE 0298/ part 2/Application of cables and flexible wires in power installations. Recommended values for current-carrying capacity of cables for fixed installations with rated voltages VO/V up to 18/30 kV.
or :
NEC [NFPA-70] art 310 for U.S.A.
You may calculate it according to IEC 60287 but there are some parameters as drying the soil around the cable, for instance, are not taken into consideration. Or for U.S.:
Neher, J.H., and McGrath, M.H. (1957), "Calculation of the Temperature Rise and Load Capability
of Cable Systems," AIEE Trans., Vol. 76, Part 3, pp. 755-772.
RE: cable selection
RE: cable selection
1)Is it a single 3 core [3 phase] cable in a single conduit [or pipe]?
2)What is the load factor [0.7-1 usually]?
3)How deep the conduit is buried?[usually 0.7-1.2 m]
4)What is the specific thermal resistance of the soil [usually 1 K.m/W]?
In order to state the reactance you need to know:
5)Is the pipe [or conduit] of steel or other ferromagnetic metal made?
6)The cable length
7)The frequency[50 or 60 Hz].
For voltage drop you need to know the rated voltage of the supply system and if the cable is for an induction motor supply, for instance, and then what will be the starting current [and better also the starting power factor].
RE: cable selection
RE: cable selection
RE: cable selection
RE: cable selection
The inductive reactance could be the same as for circular conductor cable. For 4*95 is 0.0727 ohm/km. The a.c. resistance for 70oC is 0.232 ohm/km.