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Temperature measurement using fiber optic sensors in GIS switchgear

Fiber optic temperature sensor, Intelligent monitoring system, Distributed fiber optic manufacturer in China

Fluorescent fiber optic temperature measurement Fluorescent fiber optic temperature measurement device Distributed fluorescence fiber optic temperature measurement system

Due to its advantages such as small footprint, reliable operation, and long maintenance cycle, GIS equipment has been widely applied and promoted in various voltage levels of the power system in recent years.

Why does GIS need to install a temperature measurement system

With the continuous increase in the number of GIS equipment and the increasing service life, various defects are gradually increasing, mainly manifested as heating type defects, discharge type defects, and mechanical type defects. Heating defects mainly include poor contact of conductive circuits, overall insulation moisture, aging, etc., which are the main types of defects in GIS equipment. Equipment failures caused by heating have been common in recent years, resulting in multiple equipment shutdowns and even explosions. Therefore, strengthening the detection and analysis of GIS equipment thermal defects is of great significance. With the rapid development of China’s power industry and the continuous increase in demand, gas insulated metal enclosed switches (GIS) are widely used in GIS equipment in power systems. The processing technology is strict, the technology is advanced, and the insulation medium is SF6 gas. Therefore, they have good breaking ability and slight contact burns. They have advantages such as long maintenance cycles, low failure rates, low maintenance costs, and small footprint. It is precisely because of these outstanding advantages of GIS equipment that its application in substations is becoming increasingly widespread.

GIS online temperature monitoring device

When the contact of GIS equipment is poor, overheating will occur when the load current flows due to the increased contact resistance. Overheating of contacts and busbars can cause insulation aging or even breakdown, leading to short circuits and significant accidents, resulting in huge economic losses. According to incomplete statistics, many domestic power generation companies and power companies have used GIS equipment that has to varying degrees experienced abnormal temperature changes caused by insulation aging or poor contact of components such as enclosed busbars, isolation switches, and cable heads, leading to accidents. Therefore, achieving online temperature monitoring of GIS equipment, early detection and elimination of thermal fault hazards, is of great significance for the safe and reliable operation of GIS.

Temperature measurement using fiber optic sensors in GIS isolation switchgear

Gas insulated switch gear (GIS) has been widely used both domestically and internationally due to its small footprint and excellent insulation performance. During the operation of the equipment, overheating faults of the GI isolation switch often occur due to defects such as inadequate opening and closing, insufficient insertion depth of the conductive rod, etc., resulting in contact burnout and equipment flashover, seriously threatening the safe and stable operation of the power system.

Therefore, conducting research and analysis on overheating faults of GIS isolation switches is of great significance. Accurately obtaining the temperature rise characteristics of GIS isolation switch contacts and the corresponding relationship between contact temperature rise and shell measurement point temperature rise is an important prerequisite for conducting GIS isolation switch temperature rise monitoring. When monitoring the temperature rise of GIS isolation switches, temperature monitoring points can be set on the surface of the casing corresponding to the three-phase contacts to monitor the temperature of the three-phase contacts of the isolation switch.

Temperature measurement of GIS gas switchgear busbar using fiber optic sensors

Gas Insulated Switchgear (GIS) equipment theoretically has a low failure rate, but once a failure occurs, the consequences are more serious than ordinary electrical equipment. Substation GIS busbar to ground breakdown; A three-phase short circuit fault occurred on the 220kV GIS busbar, causing arc erosion of the busbar. The reason for the above malfunction is that the GIS busbar contact causes excessive temperature rise due to the increase in contact resistance, resulting in surface welding of the busbar contact. The metal particles produced by welding cause electric field distortion, which in turn triggers an arc.

Therefore, if online monitoring of GIS bus temperature can be carried out, real-time monitoring of bus temperature and its development trend can be carried out, and overheating warning and maintenance can be organized in case of bus overheating, it will be beneficial to reduce the probability of GIS bus overheating faults and have practical significance for the safe operation of the power system. At present, the main difficulty in online monitoring of GIS bus temperature is that the sensor performance cannot meet practical needs, manifested in insufficient sensor sensitivity and temperature measurement accuracy, which cannot quickly respond to changes in GIS bus temperature.

At present, there are three main preventive measures adopted on the operation site to address the issue of overheating of GIS equipment contacts:
1. Manually observe the surface color of the contact, regularly measure the circuit resistance, and use an infrared imager to regularly monitor the temperature of fixed monitoring points. The first two require power outage maintenance of GIS equipment, and the method of measuring circuit resistance cannot accurately determine the location of poor contact parts. The infrared temperature measurement method can not disturb and damage the temperature field and thermal balance inside the GIS equipment, and can also solve the problems of high-voltage isolation and strong magnetic field interference. However, it is necessary to install an infrared temperature sensor in the GIS casing, and its measurement accuracy is greatly affected by factors such as the emissivity of the conductor metal surface and the concentration of SF6 gas. The main method is to use handheld infrared thermal imagers to regularly detect the temperature of GIS busbars, which have high resolution and temperature measurement accuracy, but are expensive. The effectiveness of testing is easily affected by environmental factors, and it is difficult to achieve integrated online monitoring systems. The resolution and accuracy of the latter infrared imaging technology are difficult to meet the requirements. In addition, the monitoring methods used above are difficult to achieve continuous measurement of GIS equipment temperature, which means online monitoring cannot be achieved.

Fluorescent fiber optic temperature measurement technology adopts the principle of fluorescence afterglow for temperature measurement, which has the advantages of not being affected by electromagnetic interference, good insulation performance, small volume, light weight, etc. It has been widely used in power equipment such as transformers, motors, switchgear, harsh experimental environments, cable joints, etc., and the technology is relatively mature. The application of fluorescent fiber optic temperature sensors in GIS conductor contact temperature monitoring can achieve accurate temperature measurement without damaging the internal electric field and temperature field of GIS, and has a wide range of application prospects.

Using fluorescent fiber optic sensors as temperature sensing elements, FJINNO designed and developed an online monitoring system for GIS bus temperature, which can monitor the real-time temperature of each interval three-phase bus and its corresponding environment in the indoor GIS bus of a 110kV substation. The comparison with the temperature measurement results of a handheld infrared thermal imager and the on-site trial operation show that the GIS busbar fiber optic temperature online monitoring system has high temperature measurement accuracy and sensitivity, and can monitor the heating status of the busbar in real time and effectively, improving the safe operation level of GIS. Fluorescent fiber optic temperature sensors were applied to GIS bus temperature monitoring, and corresponding online monitoring systems were designed, which can effectively monitor bus temperature and its changing trend, and use monitoring results to obtain the exact temperature of bus conductors.




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