Side-by-side reference

Understand the difference.

Compare the meaning, drawing context and source references of two entries. A similar graphic or shared abbreviation does not establish equivalence.

First referenceCompare with

CT RES

Symbols

Residual connection of phase CTs

A residual CT connection combines secondary currents from phase CTs to obtain a residual-current input. This is a connection arrangement that should be drawn explicitly rather than assigned an unsupported separate standard-symbol number.

Drawing use: SLD / Schematic
Application: Metering & protection
Reference family: IEC / Manufacturer

A distinction that matters

Residual connection of three phase CTs is not the same physical sensor as a core-balance CT.

Full reference

Symbols

Current transformer

A current transformer produces a secondary current related to the current in its primary conductor. A drawing uses the CT representation to show where current is measured and which metering or protection circuit receives that measurement. It does not, by itself, specify the CT ratio, accuracy class, burden or secondary connection.

Drawing use: SLD / Schematic
Application: Metering & protection
Reference family: IEC / IEEE / ANSI

A distinction that matters

A CT measures current. A VT measures voltage. Their secondary circuits and isolation/testing arrangements are different.

Full reference

Original educational previews. Follow the source references on each full entry for the appropriate standard or selected product.