RH
Relative humidity sensor
A relative humidity sensor measures moisture in air relative to the saturation condition at the relevant temperature.
Schematic
Functional block · SHHA
Switchroom humidity high alarm
Functional block · Switchrooms
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.
Browse this installation focusIn plain English
What this block does
Reports humidity exceeding the defined supervision condition at the monitored location.
A simple example
In a switchroom, water ingress, temperature, humidity and equipment-service alarms can be sent to the station controller with separate point names so an operator can identify the affected area. For this reference, the drawing identifies “Room humidity measurement” at the input and “High-humidity indication” at the output. Relative humidity varies with temperature.
What the drawings help you do
Start at the named input: Room humidity measurement. Identify its source device or document and the state represented on the drawing. Follow the named output: High-humidity indication. Cross-reference its destination and separate the command from confirmation that the equipment responded.
- Input
- Room humidity measurement
- Output
- High-humidity indication
- Application reference
- An explanation of a named drawing function or circuit relationship; the project documents define the equipment and its connections.
Read the source: Ventilation in MV substations
Schematic · SHHA
What it represents
Reports humidity exceeding the defined supervision condition at the monitored location. Environmental supervision turns measurements or contact states into clearly named room-service indications. A sensor measures a condition; the supervisory function decides whether the assigned alarm or control response is needed.
In a switchroom, water ingress, temperature, humidity and equipment-service alarms can be sent to the station controller with separate point names so an operator can identify the affected area. For this reference, the drawing identifies “Room humidity measurement” at the input and “High-humidity indication” at the output. Relative humidity varies with temperature.
Keep sensor location, alarm thresholds, delay and monitoring coverage in the room-services schedule. An environmental alarm is a diagnostic input, not a complete assessment of electrical equipment condition. 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: Room humidity measurement. Identify its source device or document and the state represented on the drawing.
- Follow the named output: High-humidity indication. Cross-reference its destination and separate the command from confirmation that the equipment responded.
- Relative humidity varies with temperature.
- Keep sensor location, alarm thresholds, delay and monitoring coverage in the room-services schedule. An environmental alarm is a diagnostic input, not a complete assessment of electrical equipment condition.
Information to show or reference
- Label the source and connection reference for room humidity measurement.
- Identify the destination and defined state of high-humidity indication.
- Record the equipment or control-document revision supporting this functional block.
- Check this application limit in the project design: Relative humidity varies with temperature.
A distinction that matters
Relative humidity varies with temperature. 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.
Ventilation in MV substations
Public technical context for switchroom environmental supervision. Heat removal, condensation and environmental design context. The application text and educational graphic are independently authored; the publisher does not certify this representation.
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.
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