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

Symbols

Earth-fault current relay

The earth-fault current relay form identifies a relay whose operating quantity is current flowing to earth. It may be fed from a core-balance CT around all live conductors, from the residual connection of three phase CTs, or from a CT in the star-point earth lead, and the source changes its achievable sensitivity.

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

A distinction that matters

An earth-fault current relay measures current to earth; an earth-fault voltage relay measures neutral displacement voltage.

Full reference

CBCT

Symbols

Core-balance current transformer

A core-balance CT measures residual current from the net magnetic effect of conductors passing through its window. It is used with earth-fault protection where the conductor arrangement and sheath routing affect the measurement.

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

A distinction that matters

A CBCT measures a combined residual quantity; a phase CT measures an individual conductor current.

Full reference

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