TEMP
Temperature indicator
A temperature indicator displays the temperature derived from its specified sensor or input.
SLD / Schematic
Symbols · WTI
Winding temperature indicator
Transformer indicator that adds a CT-heated thermal image to top-oil temperature to estimate winding hot-spot temperature.
In plain English
What does Winding temperature indicator mean?
A winding temperature indicator estimates transformer winding hot-spot temperature, which cannot easily be measured directly. A sensor in the top-oil pocket is heated by a small element fed from a CT on the load current, so the reading rises with both oil temperature and load, and its contacts control fans and give alarm and trip.
A simple example
The schematic should show the CT feeding the heater, the calibration resistor and each contact stage. The symbol does not show the thermal gradient setting, which must be adjusted to the transformer heat-run data for the reading to be meaningful.
What the drawings help you do
Trace the CT circuit feeding the thermal image heater. Identify contact stages for cooling, alarm and trip. A WTI estimates winding hot-spot with a thermal image; an oil temperature indicator reads oil temperature only.
This particular reference
Transformer indicator that adds a CT-heated thermal image to top-oil temperature to estimate winding hot-spot temperature. A WTI estimates winding hot-spot with a thermal image; an oil temperature indicator reads oil temperature only.
- Winding
- A coil of conductor inside an electrical machine or transformer.
- Normally open / normally closed
- The contact state in the normal condition defined for the drawing.
- Signal
- Electrical information passed between devices, rather than necessarily the main power supply.
Read the source: ETR-4000 and ETR-5000 transformer protection function tables · IEC graphical symbols for diagrams
Schematic / SLD · WTI
What it represents
A winding temperature indicator estimates transformer winding hot-spot temperature, which cannot easily be measured directly. A sensor in the top-oil pocket is heated by a small element fed from a CT on the load current, so the reading rises with both oil temperature and load, and its contacts control fans and give alarm and trip.
The schematic should show the CT feeding the heater, the calibration resistor and each contact stage. The symbol does not show the thermal gradient setting, which must be adjusted to the transformer heat-run data for the reading to be meaningful.
How to read it
- Trace the CT circuit feeding the thermal image heater.
- Identify contact stages for cooling, alarm and trip.
Information to show or reference
- Show heater CT
- List contact stages
- Reference gradient setting
A distinction that matters
A WTI estimates winding hot-spot with a thermal image; an oil temperature indicator reads oil temperature only.
Sources you can follow
These public references support the explanation and provide further detail. Their graphics and downloadable files remain with their publishers.
ETR-4000 and ETR-5000 transformer protection function tables
Public transformer protection context including thermal functions.
IEC graphical symbols for diagrams
IEC context for graphical symbols used in diagrams; no IEC graphic is reproduced.
About this graphic
This illustration was authored independently by Elora Grid to explain the concept. It is not reproduced from a customer drawing, an official standard graphic or a manufacturer CAD file. Its correspondence to an exact IEC or IEEE symbol identifier has not been certified.
SVG and DXF downloads contain this original artwork. DXF uses unscaled drawing units; a GA envelope supplies no product dimensions, clearances or fabrication information. Original artwork is available under CC BY 4.0. Third-party references retain their own terms.
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