How to measure temperature in high-voltage switchgear? Advantages of using fluorescent fiber optic temperature sensors to monitor busbars

Temperature measurement method for high-voltage switchgear

1. Fluorescent fiber optic sensor temperature measurement: By installing fluorescent fiber optic sensors inside the high-voltage switchgear, real-time temperature information at different locations can be obtained. This method has the advantages of high accuracy and strong resistance to electromagnetic interference, and is suitable for continuous monitoring of multi-point temperatures.

2. Infrared temperature measurement method: This is a handheld temperature measurement tool suitable for fast, non-contact temperature detection of high-voltage switchgear. The principle is to use the infrared radiation emitted from the surface of an object to be proportional to its surface temperature. By detecting and processing the infrared radiation, the surface temperature data of the target object can be obtained. When in use, simply aim at the target surface to quickly obtain the surface temperature value at that location.

3. Wireless temperature measurement method: For example, in a 10kV high-voltage switchgear, some wireless temperature measurement systems include temperature sensors installed on the sleeve of the moving contact of the trolley, and current sensors surrounding the moving contact of the trolley. The temperature sensors and current sensors are respectively connected to data receiving and processing units, and the data receiving and processing units are electrically connected to a display screen installed on the trolley style switchgear. This method can achieve real-time temperature monitoring of high-voltage switchgear. The sensor transmits the received temperature data to the data processor, which displays the specific temperature after processing, and then transmits it to the remote host through the local area network. The staff can control the temperature in real time.

4. Temperature display wax monitoring method: This is a traditional temperature monitoring method that reflects the temperature by the color change of the wax display. However, this method cannot monitor other conditions such as operating environment and load, with a single monitoring indicator and limited monitoring effect.

5. CCD camera monitoring method: It can monitor the temperature inside the high-voltage switchgear, but it also has limitations in comprehensively monitoring multiple indicators.

Principle of Fluorescent Fiber Optic Temperature Sensor for Monitoring Busbars

The fluorescent fiber optic temperature sensor for monitoring the busbar is based on the principle of fiber optic sensing. The principle of the fluorescence fiber optic temperature measurement device is that the fluorescent substance is excited by light of a certain wavelength (excitation spectrum) and emits fluorescence energy upon excitation. After the incentive is removed, the persistence of fluorescence afterglow depends on factors such as the characteristics of the fluorescent substance and environmental temperature. Structurally, the fiber optic fluorescence temperature sensing system mainly consists of temperature sensitive fluorescent material, fluorescent probe, excitation light source, coupling device, and signal acquisition and detection unit. In this system, fluorescent substances are the key to temperature measurement. When a light signal is emitted to the fiber optic temperature sensor, the fluorescent substance will feedback the light signal, and the decay time of the fluorescent light signal is a single value function of the temperature parameter. As the temperature increases, the lifetime of the fluorescent light signal decreases. By measuring the lifetime of the fluorescent light signal, the temperature value can be obtained, and the temperature measured using this method depends only on the lifetime of the fluorescent light signal and is independent of other parameters. For example, in the fluorescent fiber optic temperature measurement technology of switchgear busbars, by arranging fluorescent fiber optic sensors on the busbars, the temperature of the busbars can be monitored in real time and accurately.

Advantages of Fluorescent Fiber Optic Temperature Sensor for Monitoring Busbars

1. Strong anti-interference ability

The probe of the fluorescent fiber optic temperature sensor transmits optical signals and is not powered by electricity or current, so it is not affected by electromagnetic field interference. This characteristic is particularly important in high voltage, high current, and strong magnetic field environments such as high-voltage switchgear. Traditional electronic temperature sensors may be subject to interference in such strong electromagnetic environments, resulting in inaccurate measurements, while fluorescent fiber optic temperature sensors can work stably and accurately monitor the temperature of the busbar.

Fiber optic itself has electromagnetic insulation and good resistance to external electromagnetic interference. Even if there is electromagnetic interference generated by other electrical equipment around the switchgear, it will not affect the measurement of the busbar temperature by the fluorescent fiber optic temperature sensor, ensuring the reliability of the measurement data.

2. High measurement accuracy

The measurement principle is based on the characteristics of fluorescent substances, and the temperature is determined by measuring the lifetime of the fluorescent light signal. This measurement method has a more direct and accurate relationship with temperature. The luminescence characteristics of fluorescent substances enable the measurement results to accurately reflect the temperature changes of the busbar, and compared to some indirect temperature measurement methods, the accuracy is higher.

The probe size of the fiber optic sensor is extremely small and can be directly installed on the measured point. It can closely contact the busbar for real-time temperature monitoring, reducing errors caused by inaccurate measurement positions or thermal conduction, and further improving measurement accuracy.

3. High security

The components of fluorescent fiber optic temperature sensors, such as optical fibers, fluorescent substances, and polytetrafluoroethylene sheaths, are all insulating media that can be safely installed on busbars in strong electric and magnetic field environments. In high-voltage switchgear, the busbar is usually in a high voltage state, and using this type of well insulated sensor can avoid safety accidents caused by the sensor's own conductivity.

Due to the use of fiber optic transmission signals, there is no electrical connection during the measurement process, which avoids safety hazards such as electrical sparks that may occur due to electrical connections and ensures the safe operation of high-voltage switchgear.

4. Long lifespan and high reliability

The fluorescence fiber optic temperature probe has a long service life, and the sensor's service life can reach 30 years after installation. This is very advantageous for long-term operation of high-voltage switchgear, reducing the cost and workload of frequent sensor replacement.

The reliability of this sensor technology is high, and it is less affected by external factors such as dust, scratches, fiber bending losses, and changes in fluorescence intensity. For example, the use of a new time measurement method and closed-loop automatic gain control function in electrical applications ensures that it is not affected by these factors and can monitor the temperature of the busbar stably for a long time, detect abnormal heating conditions of the busbar in a timely manner, and prevent accidents from occurring.

5. Can monitor and establish temperature records online

It is possible to conduct online direct and accurate contact monitoring of the mother busbar, and can record the temperature changes of the monitored mother busbar for a long time, thereby establishing a temperature record. By analyzing the temperature profile, the trend of changes in the temperature of the busbar can be understood, and potential fault hazards can be detected in advance. For example, in the power system, the temperature changes of the busbar under different load conditions can be analyzed based on historical data of the busbar temperature, providing a basis for equipment maintenance and operation.

This online monitoring function can also achieve pre management by monitoring the temperature of the busbar in real time. When the temperature rises abnormally but has not yet reached the dangerous value, measures such as adjusting the load can be taken to avoid damage to the busbar due to overheating, improving the operational safety and reliability of the high-voltage switchgear.

Comparison of Fluorescent Fiber Optic Temperature Sensor and Other Temperature Measurement Methods in High Voltage Switchgear

Comparison with infrared temperature measurement method

1. Measurement method

Infrared temperature measurement is a non-contact temperature measurement method that measures temperature by receiving infrared radiation emitted from the surface of an object, without the need for direct contact with the object being measured. Fluorescent fiber optic temperature sensors belong to contact temperature measurement, and the probe needs to be installed on the busbar for temperature measurement.

The infrared temperature measurement method can quickly scan the temperature of the surface of high-voltage switchgear, with a fast measurement speed, suitable for large-scale rapid detection. For example, during the inspection process, the surface temperature of the switchgear cabinet and some exposed components can be quickly obtained. However, for the busbar inside the switchgear, due to possible obstructions, infrared radiation may not accurately reach the measuring instrument, affecting the measurement results. Although the installation of fluorescent fiber optic temperature sensors is relatively complex, once installed, they can continuously and accurately measure the temperature of the busbar without being affected by external factors such as obstruction.

2. Measurement accuracy

The accuracy of infrared temperature measurement method is easily affected by environmental factors, such as temperature, humidity, radiation, etc., which can cause deviations in the measurement results. The accuracy of infrared temperature measurement will decrease in environments with high temperature, high humidity, or interference from other heat sources. The fluorescence fiber optic temperature sensor has high measurement accuracy because its measurement principle is based on the characteristics of fluorescent substances and is less affected by external environmental factors, which can more accurately reflect the true temperature of the busbar.

3. Application scenarios

Infrared temperature measurement method is more suitable for preliminary and rapid temperature screening of high-voltage switchgear, such as quickly determining whether the equipment has obvious overheating during daily inspections. Fluorescent fiber optic temperature sensors are more suitable for long-term and accurate temperature monitoring of key components such as busbars, especially in situations where it is necessary to accurately grasp temperature trends and provide early warning of faults.

Comparison with wireless temperature measurement method

1. Signal transmission and anti-interference capability

The wireless temperature measurement method transmits temperature data through wireless signals, which may be affected by electromagnetic interference from the surrounding environment during the signal transmission process, affecting the accuracy and stability of the data. Fluorescent fiber optic temperature sensors use optical fibers to transmit optical signals. Optical fibers have good electromagnetic insulation and strong anti-interference ability, which can ensure the stability and accuracy of temperature signal transmission.

Wireless temperature measurement systems may be affected by signal interference from other wireless devices. For example, in some industrial environments with complex signals, if multiple wireless devices are working simultaneously, it may cause interruptions or data errors in wireless temperature measurement signal transmission. The optical fiber transmission of fluorescent fiber temperature sensors is not affected by these factors.

2. Installation and maintenance

The installation of wireless temperature measurement systems is relatively simple and does not require complex wiring, especially for some already installed high-voltage switchgear, it is relatively easy to retrofit and install wireless temperature measurement systems. However, sensors in wireless temperature measurement systems require battery power or other power supply methods, such as CT transformer power supply, which requires consideration of battery life and replacement issues, as well as the stability of the power supply device. When installing a fluorescent fiber optic temperature sensor, it is necessary to arrange the fiber optic cable. However, once installed, due to its long lifespan, the sensor does not need to be replaced frequently, and the fiber optic cable itself is relatively easy to maintain. As long as it is not damaged, it can work stably for a long time.

3. Measurement accuracy

The accuracy of wireless temperature measurement method depends on the precision of the sensor and the stability of signal transmission. Due to various factors, its measurement accuracy may not be as good as that of fluorescent fiber temperature sensors. The fluorescent fiber optic temperature sensor is directly installed on the busbar, which can more accurately measure the temperature of the busbar and is not affected by external factors such as dust, scratches, etc. on the measurement accuracy.

Analysis of Temperature Measurement Techniques Applicable to Different Types of High Voltage Switchgear

Removable high-voltage switchgear

Removable high-voltage switchgear is mainly used on handcarts, with superior interchangeability, which helps ensure the stability of power transmission. For this type of high-voltage switchgear, using fluorescent fiber optic temperature sensors for temperature measurement has certain advantages due to the frequent movement or operation of the handcart part.

The optical fiber of the fluorescent fiber temperature sensor is soft and bendable. During the wiring process of the movable switchgear, it can adapt to the changes in the circuit caused by the movement of the handcart, and will not affect temperature measurement due to the dynamic changes in the switchgear structure. Moreover, its high-precision and anti-interference characteristics can accurately monitor the temperature changes of the busbar and contacts inside the movable switchgear, and timely detect possible overheating problems caused by the movement of the handcart or poor contact.

Wireless temperature measurement technology is also suitable for removable high-voltage switchgear. Because wireless temperature measurement does not require complex wiring, the dynamic structure of the portable switchgear will not affect the normal operation of the temperature measurement system due to wiring connection issues. Sensors can be conveniently installed on key parts of the handcart, such as moving contacts and busbars, to achieve real-time temperature monitoring and maintain signal transmission during the handcart's movement.

Fixed high voltage switchgear

Fixed high-voltage switchgear has the advantage of being more economical due to the fixed installation of equipment and lack of mobility. For this type of switchgear, fluorescent fiber optic sensors are a suitable temperature measurement technology. Fluorescent fiber optic sensors can be deployed at multiple points inside the switchgear to achieve continuous temperature monitoring at different locations. Due to the fixed structure of the fixed switchgear, it is easy to plan the wiring and installation of fluorescent fiber optic sensors, and can comprehensively and accurately monitor the temperature distribution inside the switchgear. It can accurately monitor the temperature of the busbar and contacts, and due to its long lifespan and high reliability, it is suitable for long-term installation in fixed switchgear to continuously monitor the temperature of key components and reduce maintenance costs.

The infrared temperature measurement method also has certain application value for fixed high-voltage switchgear. When quickly detecting the surface temperature of the cabinet, the infrared temperature measurement method can leverage its advantages of non-contact and fast measurement speed, and can quickly determine the overall temperature condition of the switchgear as a preliminary temperature detection method.

Metal enclosed high-voltage switchgear

The internal components of the metal enclosed switchgear, such as circuit breakers and busbars, are installed in metal compartments, providing good enclosure. In such a closed environment, the advantages of fluorescent fiber optic temperature sensors are obvious.

Due to its strong anti-interference ability and good insulation, it can be safely and accurately installed in metal compartments for temperature monitoring of components such as busbars. Moreover, its high-precision measurement can promptly detect abnormal temperature increases caused by poor heat dissipation and other reasons in enclosed compartments.

Fiber Bragg grating sensors are also suitable for metal enclosed switchgear. By reasonably deploying fiber Bragg grating sensors in the compartment, the temperature inside the compartment can be comprehensively monitored, providing a guarantee for the safe operation of the equipment.

Metal interval type, metal enclosed box type, and open type high-voltage switchgear

For metal interval high-voltage switchgear, due to the internal interval structure, fiber optic sensors (such as fluorescent fiber optic temperature sensors and fiber optic grating sensors) can be wired reasonably according to the interval layout to accurately monitor the temperature situation in each interval, especially for temperature monitoring of key parts such as busbars and contacts.

The interior of the metal enclosed box type high-voltage switchgear is relatively enclosed, similar to a metal enclosed switchgear. Both fluorescent fiber optic temperature sensors and fiber optic grating sensors can function well, providing accurate temperature monitoring.

The structure of an open high-voltage switchgear is relatively open, and infrared temperature measurement can be used as a fast and convenient temperature monitoring method to conduct preliminary temperature screening of the main components of the switchgear. Meanwhile, fluorescent fiber optic temperature sensors can also be installed at critical locations such as busbars and contacts for precise temperature monitoring to ensure the safe operation of the equipment.

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