Most useful infrared thermal imager for live monit

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Live monitoring of zinc oxide arresters with infrared thermal imager

in recent years, the export growth of zinc oxide arresters in China's extruder products will show a stable and progressive situation. The system has been widely used. With the increase of the number of uses, the occurrence of accidents is also increasing. In order to find and detect the fault of zinc oxide arrester in time, various monitoring and test methods are used, such as measuring the resistive current of zinc oxide arrester during operation to detect the fault of zinc oxide arrester. However, due to the large interference of electric field, the sampling voltage is prone to phase shift, and the measurement results cannot reflect the real situation. For example, during the inspection of 220kV lightning arrester of No. 2 main transformer in quarry substation of our bureau, it was found that the resistive current of phase a lightning arrester was too large, but everything was normal in the test during power failure

using infrared thermography detection technology, because it is not interfered by electric field, and the heating power of zinc oxide arrester has sufficient sensitivity, it is easy to find and judge the problems of zinc oxide arrester by comparison method. Nowadays, zinc oxide surge arresters are of gapless single column structure with quality and other aspects, and the valve plate directly bears the operating voltage of the system. According to the design of operation protection parameters, the normally operated gapless zinc oxide arrester has a power frequency current of 0.5 ~ 1.0mA, which is mainly capacitive, and the resistive current accounts for only 10 ~ 20% (generally 0.1 ~ 0.3 Ma, the new mixing head directly measures the dye in the injection molding process). Therefore, the zinc oxide arrester needs to consume a certain amount of power during normal operation, so that the body has slight heating, and because the geometric distribution is relatively uniform, the surface heating is integral. In addition to the faults caused by poor manufacturing quality and operating conditions, zinc oxide arresters also have damp and valve aging faults. Individual components of zinc oxide surge arrester are affected by moisture, which shows local overheating, and valve aging is usually the common heating feature of the whole phase or multiple components. When the infrared thermal imager is used for fault diagnosis, abnormal heating, local temperature increase or decrease, or abnormal temperature distribution can be judged as abnormal according to the characteristics of the thermal image. For example, on July 5, 2001, when the quarrying substation of our bureau carried out infrared detection, it was found that the upper section of 110 kV bus phase C was overheated, and it was suspected that the lightning arrester might be damp at that time. Figure 1 shows the infrared image of the fault arrester

this arrester was a preventive test carried out on January 15. At that time, the data in the upper section of phase C was 76.4 kV at 1mA, and the current at 75% voltage was 5.2 μ A. The insulation resistance is 10 000m Ω, and the test result is qualified. Figure 2 shows the infrared image of normal arrester

from the above two infrared pictures, eelcee company has proved that the weight can be reduced by 20% - 30% (up to 50% in special cases), there is a clear difference between the fault arrester and the normal arrester. In order to ensure the accuracy of judgment, the faulty arrester was rechecked on July 8, and the result was the same as that on July 5

therefore, it is concluded that the upper section of phase C lightning arrester is damp, and it is recommended to replace it. After the replacement of the fault arrester, it was found that the data in the upper section of phase C was 64.5 kV at 1mA, and the current at 75% voltage was 526 μ A. The insulation resistance is 102 m Ω, and the test results seriously exceed the standard. After disassembly, it was found that the arrester was composed of five layers of valve plates, each layer had 10 valve plates, the first, third, fifth and ninth valve plates on the first layer had discharge traces, and the fourth and fifth valve plates on the second layer had discharge traces. The main reason is that the manufacturer did not fit the sealing rubber ring at the top of the arrester in place, resulting in uneven stress on the sealing rubber ring for a long time, aging and cracking of the sealing rubber ring, resulting in moisture on the arrester. Because the fault was found in time, an equipment accident was avoided

Figure 1 infrared picture of faulty arrester

Figure 2 infrared picture of normal arrester

(Li Hao)

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