What is a transformer temperature measurement device?

What is a transformer temperature measurement device?

The transformer temperature measurement device is an automated device specialized in real-time monitoring and controlling the temperature of critical parts of the transformer. It continuously measures the temperature inside the transformer (mainly windings and insulating oil) by means of high-precision temperature sensors and transforms the temperature signals into visualized data. More importantly, it is an intelligent protection system that can automatically perform a series of operations such as alarming, activating cooling system or directly cutting off the power supply of the transformer when the temperature reaches the preset warning value, in order to prevent the equipment from permanent damage due to overheating.

Why is temperature monitoring so important?

The life of a transformer depends to a large extent on the health of its internal insulating materials, and temperature is the primary factor affecting insulation aging. Excessive temperatures can dramatically accelerate the chemical decomposition and physical property deterioration of insulation materials, making them brittle and losing insulation strength. Therefore, accurate temperature monitoring is essential to prevent overheating damage, significantly extend the service life of the transformer by controlling the operating temperature within a reasonable range, and provide a key basis for judging the load capacity of the transformer. Abnormal changes in temperature are also an early indication of internal failure and can provide valuable information for preventive maintenance.

What are the key locations it primarily monitors?

The core task of a transformer temperature measurement device is to monitor the two locations that best reflect the health of the equipment:

1. Winding temperature: the winding is the main heat source when the transformer is running, its internal temperature is the highest point, that is, "winding hot spot temperature", is to decide whether the transformer can be safe operation of the fundamental limitations. This is the most critical monitoring indicators.

2. Top oil temperature: for oil-immersed transformers, insulating oil is the main cooling medium. The temperature of the top oil can comprehensively reflect the overall heat generation of the transformer and the cooling efficiency of the cooling system.

How does the temperature measuring device work?

Depending on the type of transformer, the principle and technology of temperature measurement varies.

Oil-immersed transformer temperature measurement: Traditionally, the "thermal simulation method" is used. In this method, the oil temperature is measured directly by means of a temperature sensing package placed in the top layer of the transformer oil. At the same time, a small current proportional to the transformer's load current flows through a heating element inside the temperature measurement device, which is placed next to the pack to simulate the temperature rise of the windings due to the load current. Ultimately, the device displays the superimposed value of the oil temperature and the simulated temperature rise, thus indirectly reflecting the hot spot temperature of the winding.

Dry-type transformer temperature measurement: this way is more direct. In the manufacturing process, the Pt100 platinum RTD and other temperature sensors are directly embedded into the internal three-phase winding. Temperature measurement device by connecting these sensors, real-time measurement of its resistance value changes, and according to the accurate "resistance - temperature" correspondence, directly calculated the real temperature of the winding.

Fluorescent fiber temperature measurement: This is currently the most advanced and accurate temperature measurement technology. It is in the manufacture of transformers, non-conductive fluorescent fiber optic sensors are laid directly on the turns of the winding. The principle is to use specific fluorescent material in the light pulse excitation, its fluorescence decay time and temperature has a precise correspondence. Since the fiber itself is insulated and not subject to any electromagnetic interference (EMI), it can achieve the most direct, safe and accurate measurement of the winding hot spot, especially for high voltage levels and important transformers with very high reliability requirements.

Core functions of the temperature measuring device

A complete transformer temperature measurement device usually has the following core functions:

1. Data Measurement and Display: Accurately measures and cycles through the real-time temperature of the windings and oil.

2. Cooling system control: when the temperature reaches the preset "start fan" value, automatically close the relay and start the fan or oil pump for forced cooling; when the temperature drops, automatically shut down the cooling system.

3. Alarm function: when the temperature exceeds the set "alarm" value, output switching signal and sound and light prompts, notify the operator to pay attention.

4. Over-temperature trip protection: when the temperature reaches the limit of the equipment can withstand the "trip" value, the output of a decisive switching signal, directly cut off the transformer power supply, the implementation of the highest level of protection.

5. Communication and remote transmission: usually equipped with RS485 and other communication interfaces, can transmit all temperature data and equipment status to the back-end monitoring system to realize remote monitoring and unattended.

Frequently Asked Questions (FAQ)

Q: Why do temperature measuring devices have two different temperature points for "alarm" and "trip"?
A: This is for graded protection and preventive management. The lower "alarm" temperature point as an early warning, prompting operators to transformer temperature is high, need to check the load or cooling system is normal, giving the opportunity for manual intervention. The higher "trip" temperature point is the last line of defense, indicating that the temperature has reached the dangerous limit, the power supply must be cut off immediately in order to prevent the equipment from burning and other serious accidents.

Q: What is the usual difference between the winding temperature and the top oil temperature?
A: This difference is called "winding to oil temperature rise", it is not a fixed value, but with the transformer load changes. The greater the load, the more current flows through the windings, the more heat is generated, and the greater the temperature difference. At full load, this difference can reach 20 to 30 degrees Celsius or even higher, depending on the design and cooling method of the transformer.

Q: What makes fluorescent fiber optic temperature measurement devices superior to traditional methods?
A: The main advantage lies in three points: First, "direct", it is directly in contact with the winding, the measurement is the real hot spot temperature, rather than analog value; Second, "accurate", high precision measurement, fast response speed; Third, "safe! Third, "safe", the fiber itself is an insulator, completely free from high voltage and strong electromagnetic field interference, fundamentally eliminating the possibility of introducing electrical risks due to temperature measurement.

Q: Can I add a temperature measurement device to my old transformer?
A: For dry-type transformers, it is very difficult to retrofit at a later stage if the sensors are not pre-embedded at the time of manufacture. For oil-immersed transformers, it is easy to retrofit or replace the traditional thermostat that measures the top oil temperature and simulates the winding temperature. However, to achieve fiber optic temperature measurement, it is necessary to return to the factory overhaul or manufacture of pre-buried fiber optic, can not be retrofitted to the field inside the winding.