BWY Series Oil Temperature Indicator

BBWY Series Transformer Top-Oil Temperature Indicator & Controller

Oil-Immersed Transformer Winding & Top-Oil Temperature Monitoring

Model:  BWY – 80   4 / 6   A  J  (TH)

1. Product Introduction

The BWY series temperature indicating controller is designed on the principle of composite temperature rise measurement. It is suitable for temperature detection and control of oil-immersed power transformers, distribution transformers, and other electrical equipment. The instrument offers excellent protective performance and operates reliably under outdoor (all-weather) conditions.

The controller is equipped with four (4) or six (6) adjustable control switches, which can be used independently to start the transformer cooling system and to trigger signal alarms. At the same time, it transmits the temperature signal to the control center for synchronous display and centralized monitoring of the transformer oil temperature.

Working Principle

The BWY controller mainly consists of an elastic element, a sensing conduit, a temperature-sensing bulb (capillary assembly), and a digital display instrument. The sealed system formed by the elastic element, sensing conduit, and temperature-sensing component is filled with a temperature-sensitive medium.

When the measured temperature changes, the volume of the temperature-sensitive medium inside the sensing bulb changes accordingly. This volume increment is transmitted through the sensing conduit to the elastic element inside the instrument, producing a corresponding displacement. After mechanical amplification, this displacement indicates the measured temperature on the dial and drives the micro switches to output ON/OFF control signals, which in turn drive the cooling system to control the transformer temperature rise.

In addition, a Pt100 platinum resistance signal is embedded in the elongated tube at the upper end of the temperature bulb. This signal is supplied to the secondary instrument in the control room for remote indication and data acquisition.

2. Model, Specification, Structure & Features

2.1 Model Designation

BWY  –  80    4 / 6    A  J   (TH)

Code	Meaning
BWY	Transformer top-oil temperature indicator & controller series
80	Linear dial scale (e.g. 0–150 °C); “80” denotes the scale type
4 / 6	Number of adjustable control switches: 4 switches or 6 switches
A	Output: Pt100 platinum resistance signal
J	Output: 4–20 mA DC analog signal
(TH)	Three-defense (salt fog / humidity / fungus) requirement, optional

2.2 Output Signal Combinations

Suffix	Output Signal	Application
A	Pt100 platinum resistance	Resistance signal for secondary instruments
J	4–20 mA DC	Standard analog signal for remote SCADA / PLC
AJ	Pt100 + 4–20 mA	Dual output for local + remote monitoring

2.3 Structural Features

• Composite sensing: measurement based on a sealed temperature-sensing system (bulb + capillary + elastic element).
• Hermetically sealed: the sensing bulb, capillary, and elastic element are filled with temperature-sensitive medium for accurate, drift-free transmission.
• Adjustable switches: four (4) or six (6) micro switches; setpoints are field-adjustable to match cooling-stage and alarm requirements.
• Remote transmission: via embedded Pt100 and/or 4–20 mA output for synchronized display in the control room.
• Weatherproof: housing designed for reliable operation in outdoor and harsh environments (optional TH version).

3. Technical Data

Parameter	Specification
Measuring principle	Composite (gas / vapor pressure) temperature rise
Measured medium	Transformer insulating oil (top oil)
Temperature range	0 – 150 °C (other ranges on request)
Scale	Linear scale, 4–6 setpoints available
Accuracy class	1.5 (refer to dial marking)
Number of switches	4 or 6 (adjustable)
Switch type	Micro switch, SPDT (single pole double throw)
Switch error	±2 °C (typical)
Contact capacity	AC 250 V / 5 A (resistive)
Remote output	Pt100 (IEC 60751) and/or 4–20 mA DC
Bulb (sensor) size	Ø14 × 150 mm (typical)
Bulb mounting thread	M27 × 2
Capillary length	Up to 6 m (customizable)
Enclosure protection	IP55 (typical, outdoor duty)
Reference standard	IEC 60076, GB/T 6451

4. Applications

• Temperature monitoring and cooling control of large power transformers.
• Cooling-system staging (fans / pumps) based on oil temperature setpoints.
• Overtemperature alarm and trip signal output for transformer protection.
• Remote temperature indication in unmanned / substation automation systems.

5. Why Choose Us

• Customizable: OEM/ODM support with flexible switch configuration and output options.
• Quality assured: 100% calibrated and tested before shipment (setpoint + remote-signal check).
• Field proven: proven outdoor reliability under all-weather and coastal conditions.
• Fast response: quotation and technical proposal with drawing within 24 hours.

6. Ordering Information

To select the correct BWY controller, please specify the following information when requesting a quotation:

No.	Required Information	Example
1	Temperature range / dial scale	0–150 °C, linear
2	Number of control switches	4 (or 6)
3	Switch setpoints (K1 / K2 / K3 / K4)	K1=55, K2=65, K3=80, K4=120 °C
4	Output signal	AJ (Pt100 + 4–20 mA)
5	Bulb / capillary length / mounting thread	Capillary 4 m, M27×2

Send us your transformer cooling scheme or setpoint list and we will provide a free technical proposal within 24 hours.