Transformer body due to oil pipeline blockage, eddy current loss, eddy current loss, internal anomaly, internal anomalies, poor core insulation insulation poor insulation, and radiator problems easily lead to abnormal transformer body temperature.
The detection of the transformer body by the infrared thermal imager and the detection of the transformer body by the infrared thermal imager can make the transformer always in a good working state, improve the service life and increase the service life, and at the same time avoid accidents and avoid accidents.
Main parts and causes of typical thermal defects in transformers The typical heating parts of power transformer equipment mainly include the following two parts:
1. Transformer body: The main cause of abnormal heating of the transformer body is due to the magnetic leakage of the main transformer resulting in local overheating of the body.
2, transformer radiator: Transformer radiator overheating fault is mainly due to the operation of the transformer to control the radiator valve fault, oil block, or radiator failure or shutdown caused.
Transformer body thermal defect characteristics description:
1. Transformer body thermal defect: The most common anomalous heating is the poor current-breaking ability of the transformer's magnetic flux leakage, and the eddy current caused by uneven magnetic field distribution generates current difference and potential difference at this location. It can cause the transformer box body or part of the connecting screw to heat up, and its thermal image feature is a layered irregular ring (as shown in the figure below) centered on the leakage magnetic flux through the area.
The temperature of the box caused by the eddy current loss generally must not exceed 95°C. If the temperature is too high, the transformer needs to be stopped for maintenance. This kind of defect can be eliminated by using a short-circuit ring.
2. Transformer radiator thermal defect: When the infrared camera is used to record normal work, the heat generated by each group of compressor radiators should be basically the same. When a fault occurs in one of the groups, when the pipeline of the transformer oil pipeline is blocked, the thermal image feature is that the blocked pipeline or radiator shows a low temperature area because it has not participated in the oil circulation, and the other parts have relatively high temperatures, and the temperature of the two parts is relatively high. Differently, the thermogram can be clearly reflected (as shown below).
Infrared thermal image detection of thermal defects in transformers is based on the judgment of DL/T 664-2008 9.3 integrated heat-generating equipment: When the defect is caused by two or more factors, it shall be a comprehensive judgment of the nature of the defect.
The overheat caused by the magnetic field and magnetic flux leakage can be processed according to the criteria of the current-heating type equipment. Treatment of thermal defects Recommendation 1. The thermal defect of the transformer body is not clearly specified in the DL/T 664-2008 9.3 specification. However, according to the actual situation on the spot, if the local box heating temperature caused by eddy current loss exceeds 95°C, the transformer needs to be shut down and overhauled. This kind of defect can be avoided by the following measures:
1) Using silicon steel sheet for magnetic flux short-circuit to eliminate magnetic leakage;
2) Replace the ordinary ferromagnetic screw with a non-ferromagnetic screw (eg stainless steel, etc.).
2. Transformer radiator heat defect treatment suggestion: This kind of situation is generally caused by mechanical failure of transformer oil circuit or abnormal operation of cooling fan/pump. When you encounter this problem:
1) First we can see if the butterfly valve controlling the radiator circuit is open. If it is confirmed that the butterfly valve is open, the motor should be stopped to inspect the defective radiator circuit and repair or replace the defective part.
2) Next, we need to find out whether the cooling fans/pumps are working during the peak load period to make them run for 20-30 minutes and look for the following:
a) Low-temperature motor (with or without operation);
b) overheated motor;
c) permanent failure;
d) Reverse flow, etc.
How to use thermal imager for transformer body detection?
1. If the transformer load is low, the local temperature rise will not be very high, and the infrared thermal imager cannot detect it. Therefore, before the transformer body detection, whether the transformer load exceeds 30% is determined, otherwise it may not be detected.
2. Transformers are often installed directly outdoors (some are also installed indoors). There are also many factors that interfere with the external environment. We recommend that:
1) During the test, care should be taken to avoid measuring the direct sunlight, especially to avoid shooting at noon.
2) If the heat map is not clear in automatic mode, you can use the automatic mode to measure the temperature range of the oil pillow first; then manually set the level and span, set the temperature range to the minimum, and include the previously measured temperature range (various models The instrument has a different minimum temperature range).
3) If there are multiple transformers at the site and the working conditions are similar, compare the temperatures of the transformer shells with one another so that the transformer body heat can be found in time.
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