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

Apparatus thermal device

Responds to the temperature of equipment or a monitored part of that equipment.

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

A distinction that matters

An apparatus thermal device can be a direct sensor or switch; a 49 function may instead use a calculated thermal model.

Full reference

Protection functions

Thermal protection

A thermal protection function responds to a thermal condition or model appropriate to the selected machine or transformer application. Its inputs and implementation vary between devices, so the number alone does not establish a sensor arrangement or a thermal model.

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

A distinction that matters

A thermal relay, temperature sensor and instantaneous overcurrent element are different devices or functions.

Full reference

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