What they use 300mm single core PVC/PVC cable for:
Main power supply from transformer to distribution panel
Used to carry high current from transformer to main switchboard.
Industrial factories
For heavy machines, large motors, compressors, and industrial equipment.
Generator connection
Connecting big generators to changeover panel or main distribution board.
Commercial buildings
Malls, hotels, hospitals, high-rise buildings for main incoming power.
Underground power installation
Suitable for duct or underground installation because of thick PVC insulation.