Editing Current transformer (section)

==High voltage types==
Current transformers are used for protection, measurement and control in high-voltage electrical [[Electrical substation|substations]] and the [[electrical grid]]. Current transformers may be installed inside switchgear or in apparatus bushings, but very often free-standing outdoor current transformers are used.  In a switchyard, ''live tank'' current transformers have a substantial part of their enclosure energized at the line voltage and must be mounted on insulators. ''Dead tank'' current transformers isolate the measured circuit from the enclosure. Live tank CTs are useful because the primary conductor is short, which gives better stability and a higher short-circuit current rating. The primary of the winding can be evenly distributed around the magnetic core, which gives better performance for overloads and transients. Since the major insulation of a live-tank current transformer is not exposed to the heat of the primary conductors, insulation life and thermal stability is improved.<ref name=SHEE11/>

A high-voltage current transformer may contain several cores, each with a secondary winding, for different purposes (such as metering circuits, control, or protection).<ref>''Protective Relays Application Guide'', (The General Electric Company Limited of England, 1975) pages 78-87</ref> A neutral current transformer is used as earth fault protection to measure any fault current flowing through the neutral line from the wye neutral point of a transformer.