Transformer Temperature Control

TR42

Temperature Control, Sensor, Monitoring Protection Relay for MV Transformers (Updated)

The TR42 is a temperature monitoring, control, and sensor relay (ANSI 49 protection relay) designed for 3-phase cast resin and dry-type transformers, regardless of voltage (kV) or power rating (kVA).

Its main function is to take real-time action based on temperature readings from the transformer windings and user-defined programming—such as activating or deactivating cooling fans, triggering alarms, or initiating trips.

The device includes an RS485 Modbus communication port for integration into SCADA or remote monitoring systems.

This transformer protection relay (ANSI 49) features four PT100 inputs for accurate temperature monitoring of dry-type or cast resin transformers. It offers two independent output contacts for controlling dual-stage fan cooling, useful during high ambient temperatures or overcurrent conditions, helping you maximize kVA output while avoiding thermal overload. 100% compatible with previous models.

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Features

4 RTD PT100 Inputs (3 wires)
Real-time temperature display for each sensor
Display and storage of the peak temperature reached by each RTD
4 independent programmable output contacts configurable from 0°C to 220°C for Level 1 alarm, Level 2 alarm, FAN1, and FAN2 control (new)
Automatic fan mode and “Always ON” option for continuous ventilation
Alarm relay for TR42 internal failure or PT100 sensor disconnection
Weekly automatic fan start to protect fan bearings from seizing
Isolated RS485 Modbus communication port for integration into SCADA and remote systems
Optional 4–20 mA analog output corresponding to temperature readings
100% backward compatible with previous models
QR code access to product documentation and tutorial videos

Technical specifications

Cast Resin transformer - Orion Italia TR42 temperature control

Scale: -10 ÷ +240 °C
Accuracy: ±1% F.S. ± 1 digit
Settings: L1, L2, FAN1, FAN2: 0 ÷ 220 °C
Supply voltage: 85÷264Vac (115÷300Vdc) or 24Vdc (select model)
Maximum power consumption: 4VA or 4W
Inputs: 4 platinum sensors PT100 with 3 wires. 500 Ohm max wire impedance.
Outputs: FAN: normally open, Imax 16A 240Vac/24Vdc resistive load (7A continuous) /1HP 240 Vac. L1,L2: change-over 5A(n.o) res. load 250 Vac.
FAULT: 5A (n.c)
Operational Temperature: 0 ÷ 50 °C
Storage Temperature: –20 ÷ 70 °C
Relative Humidity: 90% (non-condensing)
Burn in: 48 hours
Dielectric Withstand Voltage: 2 kVac, 60s
Construction: according to the VDE, UL, CEI standards.
Terminal block: draw-out terminals for 4 mm² cables (12 AWG).
Frame: In ABS self-extinguish with frontal protection (IP54).
Assembly: to be fixed in the structure through stirrups and screws.
Dimensions: 96x96x114 mm Cutout: 91-0,5x 91-0,5 mm (±0,5 mm)
Weight: 500 grams
Communication port: Insulated RS-485, insulation 1500 Vdc. Modbus RTU
Communication protocol: MODBUS RTU, function: 03h, 04h, 05h, 06h, 10h.
100% compatible with TR-42S1 & TR-42C1

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Communication

The TR42 includes an RS485 insulated communication port using the Modbus RTU protocol, allowing full integration into networks managed by supervisory systems (e.g. SCADA or PC-based monitoring).

For optimal signal integrity, connections must be made using shielded twisted pair cables.

Ideal for remote and cloud-based supervision. In ethernet is required check our ethernet model.

Functions & Signals

3 Digits Display for temperature reading
1 Digit Display for the channel identification.
Fault Led for immediate status reading
Output relays status leds
Display test function
Password protected menu
Autoscan of each input channel

PT100 Inputs

4 Programmable PT100 inputs
Select between 1 or 4 input channels
3 Wires cables PT100 sensor
Range -10 to 240°C
Short circuit or open circuit detection
Dedicated led for input status

Fan Control

2 Programmable Output relay for fan control
Select between 3 or 4 input channels
Programmable weekly fan start-up for bearing protection

Retrofit

100% compatible with older models

Same 4 inputs RTD & same cabling numbers
Same output contacts & cabling
Now with communication port in all models for future proof projects
Improved menu and security

How to Order

Order Code	Power Supply	RS-485	4-20mA	FAN1/FAN2 Contacts
TR42CMW5	85÷264Vac (115÷300Vdc)	✔	✖	✔
TR42CMB5	24Vdc	✔	✖	✔
TR42ADW5	85÷264Vac (115÷300Vdc)	✔	✔	✔
TR42ADB5	24Vdc	✔	✔	✔

Applications

Temperature Sensor Relay

The TR42 is a temperature sensor relay for dry type (cast resin) transformer and any power level (kva) or voltage (kV) , this temperature relay supports 4 PT-100 sensors with 3 wires. For indoor or outdoor applications please refer to our technicians. Our product is not compatible with PTC sensors. This Temperature sensor relay is optimized for ansi 49 (over temperature) in consequence of overcurrent. Fan control is also available on all models.

Temperature Monitoring Relay

The temperature monitoring relay TR42 has the ability to remotely share the temperature monitoring records of each transformer winding via communication port. Very important on ansi 49 (over temperature) and overcurrent situations. PT-100 sensors and Fan status are also being remotely monitored specially on outdoor or indoor installations. Dry type (cast resin) on any power level (kva) or voltage (kV)

Temperature Control Relay

Our temperature control relay TR42 has been designed to meet the requirements of a transformer protection relay in addition to control functions such as fan management to lower temperature due to overcurrents. Breaker trip is another function included to avoid dangerous over temperature that helps the transformer fire protection system

49 Protection Relay

The ANSI function 49 protection relay It is commonly used to name this type of temperature protection device for relays that prevent (indirectly) overcurrents, overheating or even fire protection by controlling and monitoring the transformers windings temperature in cast resin (dry type) models.

Transformer Temperature Protection Relay

There is a wide range of Transformer Temperature Protection Relay according to the type of transformers and its power, also different protection methods, our TR42 Relay is for Air Transformers (dry type, cast resin), the temperature protection (ansi 49) is based on monitoring by PT-100 sensors in the Transformer's windings, the relay controls these parameters and performs fan control, alarm or trip actions as programmed.

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