Functional block · TMI

Transformer moisture-monitor interface

Functional block · Substations

An independently authored application reference. The drawing shows the named function or circuit relationship; use the project legend and selected equipment documentation for its drafting form and connections.

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In plain English

What this block does

Identifies the measurement path from the installed oil or insulation moisture monitor.

A simple example

In a substation transformer bay, a protection panel receives winding-current measurements and equipment alarm contacts. An operator can then distinguish an electrical protection operation from a cooling-system or physical-condition alarm. For this reference, the drawing identifies “Moisture-monitor output” at the input and “Moisture condition information” at the output. Measurement location and temperature affect interpretation.

Moisture-monitor outputTMIMoisture condition information
A reading guide. The entry's original illustration and input/output facts describe this application.

What the drawings help you do

Start at the named input: Moisture-monitor output. Identify its source device or document and the state represented on the drawing. Follow the named output: Moisture condition information. Cross-reference its destination and separate the command from confirmation that the equipment responded.

Input
Moisture-monitor output
Output
Moisture condition information
Application reference
An explanation of a named drawing function or circuit relationship; the project documents define the equipment and its connections.

Read the source: SEL-487E transformer protection relay

Schematic · TMITransformer moisture-monitor interface: original educational illustration
Original educational illustrationSee source and graphic notes

What it represents

Identifies the measurement path from the installed oil or insulation moisture monitor. Transformer monitoring interfaces connect physical sensors and protection calculations to the station's alarms and trip logic. Temperature, oil, gas, pressure and electrical measurements indicate different conditions and require separate interpretation.

In a substation transformer bay, a protection panel receives winding-current measurements and equipment alarm contacts. An operator can then distinguish an electrical protection operation from a cooling-system or physical-condition alarm. For this reference, the drawing identifies “Moisture-monitor output” at the input and “Moisture condition information” at the output. Measurement location and temperature affect interpretation.

Identify the sensor or calculation, its monitored zone and its assigned response. Alarm and trip thresholds, sensor fitting and protection settings belong to the selected transformer documentation and the approved protection design. The functional block is an independent explanation of this named application. Equipment-specific ratings, terminal connections and operating conditions must be established in the project documentation.

How to read it

  • Start at the named input: Moisture-monitor output. Identify its source device or document and the state represented on the drawing.
  • Follow the named output: Moisture condition information. Cross-reference its destination and separate the command from confirmation that the equipment responded.
  • Measurement location and temperature affect interpretation.
  • Identify the sensor or calculation, its monitored zone and its assigned response. Alarm and trip thresholds, sensor fitting and protection settings belong to the selected transformer documentation and the approved protection design.

Information to show or reference

  • Label the source and connection reference for moisture-monitor output.
  • Identify the destination and defined state of moisture condition information.
  • Record the equipment or control-document revision supporting this functional block.
  • Check this application limit in the project design: Measurement location and temperature affect interpretation.

A distinction that matters

Measurement location and temperature affect interpretation. This reference describes the named application; it does not establish a new IEC graphical symbol, an ANSI device-function number or an exact manufacturer connection diagram.

Sources you can follow

These public references support the explanation and provide further detail. Their graphics and downloadable files remain with their publishers.

SEL-487E transformer protection relay

Public technical context for transformer protection and monitoring interfaces. Transformer protection, monitoring and measurement interfaces. The application text and educational graphic are independently authored; the publisher does not certify this representation.

SEL · Public reference checked 3 November 2026 · Link only

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. Original artwork is available under CC BY 4.0. Third-party references retain their own terms.

Entry JSON · Entry Markdown · Last editorial update: 3 November 2026

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