Dry-Type Transformer Temperature Monitoring

Where optical winding monitoring fits

Use this approach when the engineering task calls for direct measurements at winding locations where conductive sensor wiring complicates insulation or electromagnetic compatibility. Define whether the project concerns a new transformer, factory thermal evaluation or an accessible point on an existing asset. A winding temperature, an enclosure temperature and an ambient temperature answer different questions.

Plan measurement points from the thermal design

Start with the winding regions identified as thermally critical by the transformer designer. Record the phase, winding, physical position and purpose of each probe. Measurements at corresponding positions can support phase comparisons, but a point sensor cannot prove that an uninstrumented location is cooler. Ambient or cooling-air measurements provide context and should be labeled separately from winding measurements.

Installation in cast-resin and air-cooled windings

For embedded points, agree the probe drawing, fixation and optical exit route before winding manufacture or casting. The manufacturer must review compatibility with the insulation materials and manufacturing process. At accessible points, use an approved mounting method that maintains thermal contact and protects the fiber. Do not drill cured insulation or force a probe into an existing winding without an approved engineering procedure.

Protect the optical route and identify each channel

Keep the route clear of sharp edges, crushing and service activities that could pull the fiber. Obtain the minimum bend radius and connector handling instructions for the selected probe; these are not universal values. Label the probe and monitor channel against the measurement-point schedule, and retain installation drawings for commissioning and maintenance.

Compare optical probes, RTDs and infrared inspection

RTDs measure temperature through electrical resistance and may suit approved accessible locations. Fluorescent optical probes use light at the sensing point, avoiding a conductive measurement signal there. Infrared inspection requires a visible surface and does not directly measure an inaccessible internal winding point. Select the method from the location, insulation constraints and access requirements; an optical probe does not remove the need for insulation coordination.

Select the probe and monitor as a compatible system

Confirm the operating temperature envelope, required accuracy and installed response, probe dimensions, fiber length and materials against the chosen model. The monitor must support the required optical probes and channel count. Existing product pages describe available families; their listed values must not be assumed to apply to every dry-type transformer installation.

Commission readings, diagnostics and control outputs

Verify channel-to-point mapping and plausible readings under an approved commissioning procedure. Confirm how a broken or disconnected probe is reported, and distinguish that state from an overtemperature alarm. If fan control, alarm relays or a trip interface are required, confirm the selected monitor supports them and agree the control logic with the transformer engineer. Setpoints must come from the transformer design and protection requirements.

Monitoring system architecture