The ten best sensors for transformer temperature monitoring
Date: August 1, 2025 17:43:55
Transformer in the power system to bear the voltage conversion, power distribution and other key tasks, its operating temperature is directly related to the equipment life and stability of power supply. In order to accurately control the transformer temperature, a variety of advanced sensors came into being, the following are the top ten key sensors in the field of transformer temperature monitoring:
- Platinum RTD (PT100) sensors: An extremely versatile temperature sensor, the PT100 utilizes the temperature-dependent resistance of platinum metal. It has a resistance value of 100Ω at 0°C and is highly linear with temperature over a wide temperature range from - 200°C to 850°C. The PT100 sensor has an accuracy of ±0.1°C in monitoring the temperature of transformer windings. In transformer winding temperature monitoring, PT100 sensor accuracy of ± 0.1 ℃, can accurately capture the winding temperature changes, to determine the operating status of the equipment to provide reliable data. For example, in large power transformers, the Dry-type transformer thermostatThe Section monitors insulation aging trends stably over time in a variety of environments, effectively preventing thermal failures.
- Thermocouple Sensors: Based on the Seebeck effect, two different metal conductors form a closed loop that generates a thermopotential when the temperatures at the two ends are different, and the size of the thermopotential is related to the temperature difference. Thermocouple sensors are extremely responsive, typically in the millisecond range, and can quickly sense sudden temperature changes within a transformer. The measurement range is even wider, from - 270 ℃ to 2800 ℃, suitable for measuring transformer windings, core and other high temperature parts. K-type thermocouple because of the high cost-effective, in the ordinary transformer temperature monitoring is more common; S-type, B-type thermocouple by virtue of the higher accuracy and high temperature characteristics, mostly used in ultra-high-voltage, large-capacity transformers, the key parts of the temperature measurement.
- Fluorescent Fiber Optic Temperature SensorsTemperature measurement is realized by utilizing the temperature sensitivity of fluorescent materials. When a specific wavelength of excitation light is irradiated onto a fluorescent material, the fluorescence emitted by the material will change its decay rate (fluorescence lifetime) with the change of temperature, and the temperature value can be calculated by detecting the change of the fluorescence lifetime. The measurement range is from - 40°C to 260°C with an accuracy of ±0.5°C. The sensor is extremely resistant to electrostatic discharge. The sensor has a strong resistance to electromagnetic interference, the signal transmission process is not affected by strong electric and magnetic fields, and the fiber itself has excellent insulation, can be directly implanted inside the transformer high-voltage winding. In 500kV and above ultra-high voltage transformers, it can accurately monitor the hot spot temperature of the windings, and even in the strong electromagnetic environment generated by the transformer operation, it can still maintain stable measurement performance, providing accurate data for assessing the aging state of the winding insulation.
- Distributed Fiber Optic Temperature Measurement System: Measurement of the temperature field distributed along an optical fiber by transmitting light pulses into the fiber and using the temperature characteristics of the backward-scattered light in the fiber. The spatial resolution is up to 1m and the temperature measurement accuracy is ±1℃. This sensor can carry out all-round, continuous temperature monitoring of the transformer windings, oil channels, etc., and can detect local overheating hazards in time. In large oil-immersed transformers, distributed fiber-optic temperature measurement system can be arranged along the winding axial and radial, real-time mastery of the temperature distribution of the entire winding, compared with point sensors, can more comprehensively reflect the internal temperature status of the transformer, and effectively prevent failures caused by local overheating.
- Wireless Temperature SensorsThe temperature data is transmitted by wireless communication technology (e.g. LoRa, Bluetooth, ZigBee, etc.), which eliminates the need for cables and makes installation and maintenance extremely easy. Battery life is usually more than 5 years, which reduces the trouble of frequent battery replacement. In the transformer temperature monitoring scenario, it can be installed in the transformer high-voltage side, low-voltage side of the contacts, busbar connections and other parts that are not easy to wire, real-time monitoring of these key parts of the temperature. For example, in outdoor box-type transformers, wireless temperature sensors can be easily deployed at various monitoring points, and the temperature data can be transmitted to the receiving terminal through wireless signals to realize remote temperature monitoring.
- Infrared temperature sensors: Based on the principle that all objects radiate infrared rays to the outside and the intensity of radiation is temperature-dependent work. Can be non-contact measurement of transformer surface temperature, rapid access to a large area of temperature distribution image. Response time is short, generally within a few tens of milliseconds, can quickly detect the temperature anomaly area. Commonly used in transformer daily inspection, operation and maintenance personnel using handheld infrared thermometer, remote can be on the transformer tank, bushings, cable joints and other parts of the temperature measurement, timely discovery of overheating hidden trouble. In the substation large-scale transformer monitoring, can also be installed fixed infrared camera, more than one transformer for 24-hour uninterrupted monitoring, through the intelligent analysis software, automatic identification of temperature anomalies in the equipment and issue a warning.
- Thermistor SensorsPTC thermistors are categorized into positive temperature coefficient (PTC) and negative temperature coefficient (NTC) thermistors; PTC thermistors have a sharp increase in resistance with increasing temperature over a specific temperature range; NTC thermistors, on the other hand, have a decrease in resistance with increasing temperature. In transformer temperature monitoring, thermistors have low cost and high sensitivity. For example, in some small dry-type transformers, PTC thermistors are often used as temperature protection elements, when the temperature exceeds the set threshold, the resistance value changes abruptly, triggering the protection circuit, cutting off the power supply and preventing the transformer from being damaged by overheating.
- mercury thermometer: A classic contact temperature measurement tool that utilizes the principle of thermal expansion and contraction of mercury to measure temperature. Simple structure, low cost, intuitive readings. But the measurement accuracy is relatively low, generally in ± 1 ℃ or so, and the response speed is slow. In some of the temperature measurement accuracy requirements are not high for small transformers or as an auxiliary means of temperature measurement, there are still applications. However, due to the mercury is toxic, in the use and handling of the process need to follow strict safety norms, and now its use is gradually reduced.
- pressure thermometer: It consists of a temperature packet, a capillary tube and an indicator head, which is filled with a temperature-sensitive medium (e.g., gas, liquid or steam). When the temperature changes, the volume of the medium in the package expansion or contraction, through the capillary tube to transfer the pressure change to the meter head, so as to indicate the temperature value. Measuring range is wide, up to - 80 ℃ to 400 ℃, and easy to observe the reading. In large oil-immersed transformers, the pressure thermometer is often used as an on-site temperature display device, installed in the transformer tank wall, operation and maintenance personnel can directly read the oil temperature. It has good anti-vibration performance and is suitable for working under the vibration environment of transformer operation.
- Semiconductor Temperature Sensors: Based on the principle that the electrical characteristics of semiconductors change with temperature, e.g., the forward voltage of a PN junction is negatively correlated with temperature. It has the advantages of high sensitivity, good linearity, small size and fast response speed. In the transformer temperature monitoring system, it can be used in occasions with high requirements for temperature measurement accuracy and response speed, such as temperature control of transformer cooling system. Through precise sensing of oil temperature or winding temperature, timely adjustment of cooling fan speed or oil pump flow, to realize efficient heat dissipation, to ensure the stable operation of the transformer.
