An off-circuit tap changer (OCTC), also known as a no-load tap changer (NLTC) or de-energized tap changer (DETC), is a device that changes the voltage of a transformer when the transformer is not energized:
Description
An off-circuit tap changer (OCTC) A simple switch that’s usually mounted near the winding tappings and is submerged in oil.
Use
An off-circuit tap changer (OCTC) Used when the transformer’s turn ratio doesn’t need to be changed often and it’s okay to de-energize the transformer.
Operation
An off-circuit tap changer (OCTC) The transformer must be powered off before changing the tap position because the load current’s disconnection can cause a short circuit or burn out the tap changer.
Maintenance
An off-circuit tap changer (OCTC) To prevent contact resistance from increasing, the tap changer should be operated through its full range a few times during regular maintenance.