IMD
Insulation monitoring relay
Relay that continuously checks insulation resistance of an unearthed (IT) system to earth and alarms on a first fault.
Schematic / SLD
IEEE / ANSI · IMD
ANSI/IEEE Insulation monitoring relay form
IEEE-library form of insulation monitoring relay: relay that continuously checks insulation resistance of an unearthed (IT) system to earth and alarms on a first fault.
In plain English
What does ANSI/IEEE Insulation monitoring relay form mean?
This reference locates insulation monitoring relay in Autodesk's IEEE-oriented miscellaneous relays family. An insulation monitoring relay is connected between the conductors of an unearthed (IT) system and earth, and injects a measuring signal to determine insulation resistance. It warns when insulation falls below its setting so a first fault can be located before a second fault causes a trip. The public library uses HCR1F44 for its horizontal representation; this is a vendor block name, not an IEEE standards symbol number.
A simple example
Trace the measured quantity or initiating control signal separately from the output contacts. The device tag links the sensing or operating element to the controlled circuit; settings, reset behaviour and the actual terminal arrangement belong in the selected equipment documentation.
What the drawings help you do
The symbol shows the device and its connections but not the measuring method, which matters on systems with drives or large DC components. Only one insulation monitor should normally be active on a galvanically connected system, so the drawing should show any disconnection or interlock between parallel systems. Check that only one monitor is active on each connected IT system. An insulation monitoring relay measures insulation resistance of an unearthed system; a residual current monitor measures leakage current in an earthed system. The linked functional counterpart explains the same operating role in its own drawing context; agreement of every detailed convention mark is not asserted.
This particular reference
IEEE-library form of insulation monitoring relay: relay that continuously checks insulation resistance of an unearthed (IT) system to earth and alarms on a first fault. An insulation monitoring relay measures insulation resistance of an unearthed system; a residual current monitor measures leakage current in an earthed system.
- DC
- Direct current: electricity flowing in one direction.
- Normally open / normally closed
- The contact state in the normal condition defined for the drawing.
- Coil
- A wound conductor that can produce a magnetic field when energised.
Read the source: Autodesk IEEE Symbol Preview: Miscellaneous Relays · IEC graphical symbols for diagrams
IEEE / ANSI · Insulating Relay
Autodesk IEEE Symbol Preview: Miscellaneous Relays, block HCR1F44. Matching functional counterpart linked separately. Independently drawn educational geometry; not a certified IEEE glyph or database identifier.
Shown as an independently authored educational illustration. Use the cited publication and drawing legend to verify the required drafting form.
Schematic / SLD · IMD
What it represents
This reference locates insulation monitoring relay in Autodesk's IEEE-oriented miscellaneous relays family. An insulation monitoring relay is connected between the conductors of an unearthed (IT) system and earth, and injects a measuring signal to determine insulation resistance. It warns when insulation falls below its setting so a first fault can be located before a second fault causes a trip. The public library uses HCR1F44 for its horizontal representation; this is a vendor block name, not an IEEE standards symbol number.
Trace the measured quantity or initiating control signal separately from the output contacts. The device tag links the sensing or operating element to the controlled circuit; settings, reset behaviour and the actual terminal arrangement belong in the selected equipment documentation.
The symbol shows the device and its connections but not the measuring method, which matters on systems with drives or large DC components. Only one insulation monitor should normally be active on a galvanically connected system, so the drawing should show any disconnection or interlock between parallel systems. Check that only one monitor is active on each connected IT system. An insulation monitoring relay measures insulation resistance of an unearthed system; a residual current monitor measures leakage current in an earthed system. The linked functional counterpart explains the same operating role in its own drawing context; agreement of every detailed convention mark is not asserted.
How to read it
- Check that only one monitor is active on each connected IT system.
- Identify alarm outputs and test button wiring.
Information to show or reference
- Show system and earth connections
- State alarm thresholds
- Reference interlock between parallel monitors
A distinction that matters
An insulation monitoring relay measures insulation resistance of an unearthed system; a residual current monitor measures leakage current in an earthed system.
Sources you can follow
These public references support the explanation and provide further detail. Their graphics and downloadable files remain with their publishers.
Autodesk IEEE Symbol Preview: Miscellaneous Relays
Public IEEE-oriented Miscellaneous Relays table explicitly lists HCR1F44 as Insulating Relay. This supports the vendor convention context, not reproduction of the publisher graphic.
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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