How to select cable size?

Before you select kind of cable for your consumer, you need to calculate expected operating current of cable which depends of rated power of your consumer. After that, before you select kind of cable for your consumer, you need to check size of cable which needs to satisfy next conditions:

1. you need to check cable if it satisfies limits in normal conditions without consequences in aspect of warming (normal work),

2. you need to check cable if it satisfies limits in abnormal conditions without consequences in aspect of warming (short circuit).

1. when you want to check cable if it satisfies limits in normal conditions, you need to choose installation place (trench, concrete channel etc.), you need to know heat resistance of land, you need to know appropriate temperature of land and you need to calculate number of cables in installation place.

I calculated=number of cables*k1*k2*k3*k4*I rated cable>I rated (consumer)
k1 depends of installation place,
k2 depends of heat resistance of land,
k3 depends of appropriate temperature of land,
k4 depends of number of cables

2. when you want to check cable if it satisfies limits in abnormal conditions, you need to calculate expected current of short circuit and heat impulse at the place of installation.

If your cable satisfies these requirements, then you made the right choice.