Comparison of Temperature Monitoring Programs for Dry-type Transformers vs Oil-immersed Transformers

• Temperature Monitoring of Dry-Type Transformers: PT100 platinum resistance thermometers are embedded directly into the ends of the windings, and the temperature controller displays the three-phase winding temperatures in real time. The temperature controller automatically regulates the system based on preset thresholds.Cooling FansStart/stop; triggers an alarm and trip protection when the temperature exceeds the limit
• Temperature Monitoring of Oil-Filled Transformers: AdoptionBWYThe series of oil-surface thermostats measure the temperature of the top layer of oil,BWRThe series of winding temperature controllers indirectly estimate the temperature of winding hotspots using a thermal simulation method. They are mounted on the outside of the oil tank, eliminating the need to install sensors inside the windings.
• Core differences: Dry-type transformers use direct temperature measurement, with sensors located inside the windings; oil-immersed transformers use indirect temperature measurement (direct oil-level measurement and winding thermal simulation), with sensors located outside the tank

1. Fundamental Differences in Monitoring Methods

2. Dry-type transformer thermostatFeatures and Specifications

The model numbers of dry-type transformer temperature controllers are identified by suffix letters indicating their functions: D stands for digital temperature display, E stands for over-temperature alarm output, F stands for automatic cooling fan control, G stands for RS485 serial communication, and I stands for three-phase load current monitoring. When selecting a model, choose the corresponding suffix based on the required combination of functions. For example, if remote monitoring is required, a model with the "G" suffix must be selected.

The thermostat can be set to multiple temperature control points: fan start temperature (typically 100°C), fan stop temperature (typically 80°C), over-temperature alarm temperature (typically 130–150°C), and over-temperature trip temperature (typically 150–170°C). All thresholds can be adjusted based on the transformer’s insulation class and operating environment.

3. Key Considerations for Configuring Temperature Controllers for Oil-Filled Transformers

The oil-level temperature controller (BWY series) is equipped with 2 to 6 sets of adjustable electrical contacts; the number of contacts can be selected according to control requirements. The winding temperature controller (BWR series) detects the load current via a current transformer, and the heating element generates a temperature rise proportional to the copper loss. When used together, these devices enable oil-level temperature indication, winding hotspot temperature estimation, automatic cooling control, over-temperature alarms, and trip protection.

4. Frequently Asked Questions FAQ

4.1 Q: Can a temperature controller designed for dry-type transformers be used with oil-immersed transformers?

A: No. Temperature controllers for dry-type transformers are designed to receive signals from PT100 sensors, whereas temperature controllers for oil-immersed transformers use a mechanical temperature control system consisting of a temperature sensor assembly, a capillary tube, and a Bourdon tube. The sensor interfaces and installation methods for the two are completely different, so they are not interchangeable.

4.2 Q: Can the functional suffix of the thermostat be upgraded later?

A: Some models support upgrades by replacing internal functional modules, but this must be performed by the manufacturer. We recommend selecting the required functional configuration at the time of purchase to avoid the cost of retrofitting later.

4.3 Q: Must dry-type transformers be equipped with fan control functionality?

A: This feature is required if the transformer is equipped with a cooling fan. The fan control function (designated by the suffix "F") automatically starts and stops the fan based on the winding temperature, ensuring effective heat dissipation while preventing wasteful prolonged idling of the fan. If the transformer uses natural cooling, this function is not required.

4.4 Q: What is the maximum length of the capillary tube for an oil-filled thermostat?

A: The standard capillary tube is typically several meters long, which is sufficient to connect the top of the transformer tank to the nearest thermostat. If you have special installation requirements, please contact the manufacturer to order a longer capillary tube.

4.5 Q: Can temperature monitoring for both types of transformers be consolidated onto a single platform?

A: Yes. For substations equipped with both dry-type and oil-immersed transformers, by connecting the signals from each transformer’s temperature controller to a unified integrated monitoring platform or SCADA system, you can view the temperature data for all transformers on a single interface.

Disclaimer: The content of this article is for technical exchanges and reference only, and does not constitute any form of procurement commitment or contract offer. Product technical parameters, configuration programs and prices are subject to the actual signed contracts and technical agreements.

Need a transformer temperature monitoring solution? Contact Innotongda for assistance in selecting dry-type or oil-immersed temperature controllers. Service Hotline: 13959168359 (also on WeChat).