Energy needs measurement, protection and revenue metering (billing). ELEQ transformers.
HVDC connections can either be landed or dug or sealed as sea cables. Direct current through these cables goes unlike the alternating current which goes through the entire mains. For long distances, alternating current is not suitable because of the risk of the shine effect, induction between the cables and also the influence of water. This water will provide additional resistance to the cable and can ultimately lead to heat development and unprofitable cables. This is why the direct current is used for very long distances. To transformer this direct current transformers are needed.