The HV-Transformer Upgrade is an upgrade added by GregTech 4, as an upgrade of the Transformer Upgrade. It can only be applied to machines that accept 512 EU/t (HV) or above. With it, it increases the maximum energy of a machine by one tier; just like the Transformer Upgrade. One HV-Transformer Upgrade with allow it to use 2048 EU/t (EV), two upgrades will allow it to use 8192 EU/t (IV).
Upgrades are applied by right-clicking a machine, and cannot be removed, even with a Wrench.