A current transformer (CT) is a type of transformer that reduces or multiplies alternating current (AC), producing a current in its secondary which is proportional to the current in its primary.

What happens if a CT is left open circuited?

When CTs are connected to live circuits, they can generate high voltages if left open-circuited, leading to electrical shocks or equipment failures. By using shorting blocks, technicians can temporarily bypass the CT, neutralizing the risks associated with high voltage generation.

How do you test a current transformer?

Current transformer (CT) testing ensures accuracy and safety by verifying ratio, polarity, insulation, and saturation, usually involving excitation, ratio, and insulation resistance tests (Megger). Key tests include checking for magnetization (knee point), ensuring proper primary-to-secondary ratio, and verifying correct polarity, which are vital for protective relaying and metering accuracy.