What is prohibited while a current transformer is energized?

When a current transformer is energized, opening the secondary circuit is prohibited because it can create a dangerous situation that may lead to excessive voltage generation. Current transformers work by producing a secondary current that is proportional to the primary current flowing through the transformer. When the secondary circuit is opened while the transformer is energized, the magnetic circuit is broken and, without a load, the inductive nature of the transformer can cause the voltage at the open terminals to rise to a dangerously high level. This high voltage can pose significant risks, including electric shock or damage to the equipment and the transformer itself.

Maintaining a closed secondary circuit during operation ensures that the current transformer functions safely and effectively, providing accurate current readings without risking the safety of personnel or equipment. Proper procedures dictate that maintenance or testing activities involving current transformers require the secondary circuit to be closed and properly loaded to avoid these hazards.