Oil-immersed transformer temperature indication and monitoring[email protected]
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Transformer monitoring application

Transformer Cooling, Alarm and Trip Control

Translate temperature indication into dependable cooling, alarm and protection actions without confusing contact duty, set point and measured value.

How Does Transformer Cooling, Alarm and Trip Control Work?

Transformer temperature contacts are adjustable switches operated by an OTI or WTI mechanism. Projects assign them to cooling stages, a high-temperature alarm or a trip input. Set points and contact duties must be coordinated with the transformer thermal design, relay logic and final wiring diagram.

Give every contact a defined job

The instrument may provide two, four or six adjustable contacts. Each contact should have a written function such as fan stage one, fan stage two, high-temperature alarm or trip initiation. The terminal drawing must show whether an interposing relay is used.

The contact rating printed for an instrument does not automatically authorize direct motor switching. Review the actual inductive load, control voltage and relay design. Interposing relays can separate the measuring instrument from higher-duty circuits.

Choose set points from transformer engineering data

Cooling and alarm set points should come from the transformer design, specified temperature limits and protection study. Copying a common value from another transformer can cause unnecessary cooling or delayed protection.

The WTI reflects a load-related simulated winding value, while an OTI reflects top oil. Their contacts may therefore use different settings and serve different purposes. The commissioning record should state both the set point and the variable it represents.

Manage switching differential and sequence

Mechanical temperature switches include a switching differential. A contact that starts a fan at a rising temperature will release at a lower value. The differential prevents rapid cycling but must be considered when coordinating stages.

Sequence the stages so cooling starts before alarm and alarm occurs before any temperature-based trip, subject to the approved design. Test the actual switch behavior rather than assuming the pointer setting equals the final operating point exactly.

Prove the logic before service

Functional testing should trace every contact from the instrument terminal to the final fan, pump, annunciator or protection relay input. Confirm contact state, wiring, interlocks and fail-safe behavior.

Label and seal approved set points where required. Periodic maintenance should test contact operation and inspect for capillary damage, moisture ingress or pointer error.

Checks Before Model Selection

Switching motor loads beyond contact ratings

Using identical set points for different transformer designs

Assigning a WTI trip from an unverified CT circuit

Leaving no hysteresis or functional test record

Transformer Temperature Products for This Application

Compare the measured variable, contacts, signal and mechanical interface before choosing the final model.

Sales and engineering support

Plan Transformer Cooling, Alarm and Trip Control

Tell us the transformer type, required temperature range, contact functions, output signal, capillary length, quantity and destination. We will help you identify a suitable model and send the available technical documents.

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