What Is a Transformer Oil Temperature Indicator?
A transformer oil temperature indicator is a mechanical temperature indicating and control instrument used on oil-immersed transformers. It measures the top oil temperature through a sensing bulb installed in the transformer oil pocket and displays the temperature on a local dial.
The instrument is commonly used as a transformer oil temperature gauge, top oil temperature controller or oil temperature indicator in transformer control systems. It can provide local temperature indication, switch contact output and remote signal transmission for transformer operation, cooling control and over-temperature alarm.
Product Positioning
This product is suitable for transformer oil temperature measurement, oil temperature gauge replacement, transformer top oil temperature monitoring, cooling fan control, alarm output and transformer temperature controller applications.
How the Transformer Oil Temperature Indicator Works
The temperature sensing bulb is inserted into the transformer oil pocket. When the transformer oil temperature changes, the temperature sensing medium inside the sealed system expands or contracts. This change is transmitted through the capillary tube to the elastic element inside the instrument.
The mechanical displacement is amplified by the internal mechanism to drive the pointer, showing the transformer oil temperature on the dial. At the same time, the instrument can drive adjustable temperature switches for alarm, cooling or protection control.
Top Oil Temperature Sensing
The sensing bulb detects transformer top oil temperature from the oil pocket and transfers the temperature change to the indicator body.
Local Dial Indication
The dial provides a direct on-site reading, allowing operators to check transformer oil temperature during inspection.
Switch Contact Control
Adjustable temperature switches can be used for cooling system start, over-temperature alarm or protection signal output.
Remote Signal Output
The Pt100 resistance signal can be connected to a digital display temperature controller or converted through secondary instruments for remote monitoring.
Technical Specifications
| Specification Item | Standard Configuration |
|---|---|
| Product name | Transformer Oil Temperature Indicator |
| Typical model | BWY-802 / BWY-803A series |
| Application | Oil-immersed transformer top oil temperature indication and control |
| Output signal | A-Pt100 resistance signal |
| Working conditions | Ambient temperature -40°C to +55°C, relative humidity ≤95% |
| Temperature measurement range | 0-100°C or 0-120°C |
| Accuracy | Class 1.5; maximum allowable error for 0-120°C detection point is ±1.8°C |
| Switching error | ±2°C |
| Switch rated power | AC220V / 3A, DC220V / 1.5A |
| Protection level | IP55 |
| Temperature bulb size | Diameter Φ14, insertion depth ≥150mm |
| Mounting thread | M27 × 2 |
| Capillary length | 5m |
| Switch configuration | Three adjustable temperature switches |
| Remote display option | Can be connected with digital display temperature controller |
Main Functions
Transformer Oil Temperature Indication
The instrument provides direct local indication of transformer oil temperature, helping operators quickly check the thermal condition of the transformer during routine inspection.
Top Oil Temperature Control
The product is suitable for top oil temperature control in oil-immersed transformers. It can be used to trigger cooling equipment or alarm signals according to preset temperature points.
Remote Temperature Display
The Pt100 resistance signal can be transmitted to a remote digital display instrument, allowing oil temperature to be viewed in a control room or transformer control cabinet.
Cooling System Start Control
The adjustable temperature switches can be used to start cooling fans, oil pumps or other transformer cooling equipment according to the control circuit design.
Over-Temperature Alarm
The switch contacts can provide alarm output when transformer oil temperature reaches the set threshold.
Transformer Temperature Controller Integration
The instrument can work with a transformer temperature controller or secondary display instrument for synchronous display, control and remote monitoring.
Product Structure
| Part | Function |
|---|---|
| Dial Indicator | Shows transformer oil temperature locally |
| Temperature Sensing Bulb | Installed in the transformer oil pocket to sense top oil temperature |
| Capillary Tube | Transfers temperature change from the sensing bulb to the indicator body |
| Elastic Element | Converts internal medium expansion into mechanical displacement |
| Temperature Switches | Provide alarm, cooling or protection control output |
| Pt100 Output Unit | Provides resistance signal for remote display or secondary conversion |
Typical Applications
Oil-Immersed Power Transformers
The indicator is used for top oil temperature indication, cooling control and alarm output on oil-immersed power transformers.
Distribution Transformers
For distribution transformers, the instrument provides local oil temperature reading and remote temperature signal support.
Transformer Cooling Control Cabinets
The switch contacts can be connected to transformer control cabinets for cooling fan control, oil pump control or over-temperature alarm logic.
Substation Transformer Monitoring
The Pt100 signal can support remote temperature display in substation control rooms or transformer monitoring panels.
Transformer Temperature Controller Systems
The product can be used with a transformer temperature controller or digital display instrument for synchronous temperature display and control.
Application Matching Table
| Application | Function Needed | Recommended Use |
|---|---|---|
| Transformer Local Inspection | On-site oil temperature reading | Local dial indication |
| Cooling Control | Fan or oil pump start signal | Adjustable switch contact output |
| Over-Temperature Alarm | Alarm signal at high oil temperature | Temperature switch setting |
| Remote Display | Temperature display in control room | Pt100 signal to digital display controller |
| Monitoring System Integration | Standard signal or communication output | Secondary instrument conversion to 4-20mA, 0-5V or RS485 |
How to Select a Transformer Oil Temperature Indicator
Confirm Transformer Type
Check whether the product will be used on an oil-immersed power transformer, distribution transformer or special transformer.
Confirm Temperature Range
Select the required transformer oil temperature range according to transformer operating condition and alarm setting requirement.
Confirm Mounting Thread
Check the transformer oil pocket thread and sensing bulb insertion depth before selecting the instrument.
Confirm Capillary Length
Choose the capillary length according to the distance between the oil pocket and the instrument mounting position.
Confirm Output Requirement
Confirm whether the project needs only local indication, switch contacts, Pt100 remote signal or secondary conversion output.
Confirm Control Points
Define the cooling start, cooling stop, alarm and protection temperature points according to transformer control logic.
Recommended Information for Selection
| Required Information | Example |
|---|---|
| Transformer type | Oil-immersed power transformer or distribution transformer |
| Temperature range | 0-100°C or 0-120°C |
| Remote output | Pt100 signal, digital display controller, 4-20mA conversion or RS485 conversion |
| Control function | Cooling control, alarm output or over-temperature protection |
| Mounting interface | M27 × 2 thread or project-specific oil pocket size |
| Installation distance | Distance between oil pocket and indicator mounting position |
Frequently Asked Questions
What is a transformer oil temperature indicator?
It is an instrument used on oil-immersed transformers to measure and display transformer top oil temperature.
What does OTI mean?
OTI means Oil Temperature Indicator. It is used to indicate transformer oil temperature, usually top oil temperature.
Is this product used for winding temperature?
No. This product is mainly used for transformer oil temperature indication and control. Winding temperature indicator products are selected separately when winding temperature simulation is required.
Can it output a remote signal?
Yes. The product can output a Pt100 resistance signal for connection with a remote display or digital temperature controller.
Can the Pt100 signal be converted to 4-20mA or RS485?
Yes. Through a suitable secondary display or conversion instrument, the Pt100 signal can be converted to 4-20mA, 0-5V or RS485 communication output.
Can it control transformer cooling equipment?
Yes. The adjustable temperature switches can be used for cooling fan start, oil pump control or over-temperature alarm according to the control circuit design.
Where is the temperature sensing bulb installed?
The sensing bulb is installed in the transformer oil pocket to detect top oil temperature.
What information is needed before selection?
Transformer type, temperature range, mounting thread, insertion depth, capillary length, output requirement and control function should be confirmed before selection.
Transformer Oil Temperature Indicator for Oil-Immersed Transformer Control
The transformer oil temperature indicator provides top oil temperature indication, switch contact output and Pt100 remote signal transmission for oil-immersed transformers. It is suitable for transformer oil temperature gauge applications, cooling control cabinets, substation monitoring panels and transformer temperature controller systems.
