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CABLE SIZING

The proper sizing of electrical cables is important to ensure that it can withstand the worst short circuit currents flowing through, operate continuously under full load without being damaged, provide the load with a suitable voltage and avoid excessive voltage drops, and ensure operation of protective devices during an earth fault. The cable sizing system study can be done individually for each electrical cable that needs to be sized, or by producing cable sizing waterfall charts for groups of cables with similar characteristics.

 

The cable sizing methods differ across various international standards and some of the standards emphasise certain things over others. Nevertheless, the general guidelines underlying any cable sizing analysis do not change. The processes involved in the general method for cable sizing study are gathering data about the cable, including its installation conditions and the load that it will carry; determining the minimum cable size based on continuous current carrying capacity; establishing the minimum cable size based on voltage drop considerations; determining the minimum cable size based on short circuit temperature rise; confirming the minimum cable size based on earth fault loop impedance; and finally, deciding the cable based on the highest of the sizes calculated in the earlier steps.

 

The elensol cable sizing system study calculates optimal and alternative cable sizes for phase conductors based on load current, voltage drop, motor minimum starting voltage, short circuit current, protective device requirements and harmonic spectrum. By using our cable sizing study, load current can be based on the full-load amp of any element on the one-line diagram or as a user-specified value. Our customers can decide the cable size instantly based on the cable derated ampacity for any type of installation.