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

87Q

Protection functions

Negative-sequence differential protection

Compares negative-sequence current information across a differential protection zone.

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

A distinction that matters

Sequence differential 87Q is not the same as local negative-sequence overcurrent 51Q; it compares quantities across a zone.

Full reference

Protection functions

Differential protection

Differential protection compares quantities associated with the boundaries of a protection zone according to the selected implementation. Equipment and application suffixes can distinguish transformer, busbar, line or other arrangements. The base number alone does not define the zone or measurements.

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

A distinction that matters

Transformer differential, busbar differential and other differential applications are not interchangeable merely because they share the base number 87.

Full reference

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