Current transformer (CT)

IEC 60617 (single-line diagram symbols)

Drawn as

A small circle around the conductor line, with secondary leads to a meter or relay.

Meaning

Steps down current for protection relays and meters. Inside a switchboard it is part of switchgear. A free-standing outdoor CT becomes instrument-transformer.

Variants

Ratio (e.g. 400/1 A) and class are written beside it
Some legends draw a small loop on the conductor