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

Protection functions

Undervoltage

An undervoltage function detects a voltage condition below its configured criteria. On an SLD, the number identifies the function rather than a particular relay product or its voltage and time settings.

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

A distinction that matters

An undervoltage element and an undervoltage release are related voltage concepts but can describe different equipment and operating arrangements.

Full reference

Protection functions

Overvoltage

An overvoltage function detects a voltage condition above its configured criteria. The full designation and manufacturer information identify the measured quantity, implementation and application. A generic 59 reference does not establish trip values or time delays.

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

A distinction that matters

A phase overvoltage element and a residual-voltage or neutral-displacement application may use different measurements and suffixes.

Full reference

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