HT MEANS MORE THAN 500V
LT MEANS LESS THAN 450V
Michael Faraday (1791-1867) an Englishman, made one of the 
most significant discoveries in the history of electricity: 
Electromagnetic induction. His pioneering work dealt with 
how electric currents work. Many inventions would come from 
his experiments, but they would come fifty to one hundred 
years later.

Basic difference is the dielectric strength/ thickness of 
insulation. For LV PVC is OK. However, for HT cable cross 
linked poly ethylene(XLPE) is used.

In HT cable used single core but in LT used multicore. 
Insulation desine with carrying voltage. HT cable unarmoud 
but LT is armoud.

HT is High Tension Cable whereas LT is Low Tension Cable

HT cable have only 3 core.having semiconductor layer on 
core insulation.
LT have 3.5/4 core.

In High Tension cable there is no Neutral.In market will 
get only 1,3 core cbles where as in LT cable there is a 
neutral U have to prefer for 3.5 or 4 core cable.HT cable 
having Screen to avoid voids and cavities.