Tension is a French word for Voltage. A low-tension line is a low voltage line and a high-tension line is a high voltage line. In India LT supply is of 400 Volts for three-phase connection and 230 Volts for single-phase connection. High tension or HT supply is applicable for bulk power purchasers who need 11 kilo-Volts or above.

Most small consumers of electricity like individual houses, shops, small offices and smaller manufacturing units get their electricity on LT connection. HT is applicable for bulk purchasers of electricity like industries (big manufacturing units), big offices, Universities, hostels and even residential colonies (if the apartment complexes purchase together in bulk). The tariff structures of most state distribution companies are different for LT and HT.