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

51N

Protection functions

Time neutral-overcurrent protection

Supervises neutral or residual overcurrent with the configured timing characteristic.

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

A distinction that matters

Neutral/residual 51N does not determine whether the source is a neutral CT or a residual sum; show the source explicitly.

Full reference

Protection functions

Time overcurrent

A time overcurrent function detects an overcurrent condition using the configured time characteristic. Depending on the device and application, the implementation can include inverse-time or definite-time behaviour. Its number does not specify a curve, pickup or delay.

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

A distinction that matters

Functions 50 and 51 describe different time behaviour. One multifunction relay can implement both without becoming two separate physical devices.

Full reference

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