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

51Q

Protection functions

Time negative-sequence overcurrent

Supervises negative-sequence current using a time-dependent operating criterion.

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

A distinction that matters

51Q is a negative-sequence time-overcurrent element; generator thermal unbalance protection may use a separate machine-damage model.

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.