The contact resistance of the tail wire contact of AAAC Cable terminal (especially outdoor, sometimes connected by copper aluminum two different metals) will increase under the influence of long-term load and fault current, which will lead to overheating. When the line fails, the fault current flows through the contact, which will burn the contact. Measuring the contact temperature under the condition of no power failure, that is, to conduct live temperature measurement (preferably when the load is large), is an effective measure to monitor and check the contact condition. There are three main methods to check the contact temperature.
(1) Paste the temperature wax sheet: the temperature wax sheet is divided into three types: 60 ℃, 70 ℃ and 80 ℃, and are respectively expressed in different colors, and the commonly used ones are yellow, green and red. The temperature range can only be roughly checked by using the temperature wax plate. The reaction time is slow and the paste is not convenient. It is less used at present.
(2) Discoloration thermometer: this kind of color change thermometer is a surface measuring tool. It was used to monitor the temperature of heating working parts during welding in shipbuilding industry. It is used to indicate temperature according to the color changing characteristics of pigment in the pen at a certain temperature. The temperature measurement is quick and easy to use. Generally, the one with lower temperature can be selected for ABC Cable line. For example, the color changing temperature pen with color change temperature of 70 ℃ is selected, and it is marked as the original color. If the temperature is more than 70 ℃, it will become lake blue. The price of this color change thermometer is also cheaper. The temperature measurement reaction is fast (only 1-2s), and it is convenient to use.
(3) Infrared thermometer and thermal imager: the temperature wax plate and the color change thermometer shall be directly contacted with the live equipment, and the insulation rod shall be used for operation. Infrared thermometers and thermal imagers can measure temperature outside the measured point, so they are safe and reliable, and their measurement accuracy is much higher than the above two. The commonly used infrared thermometers or thermal imagers generally adopt portable type. See Fig. 9-4 and Fig. 9-5. The measuring distance is 5m, 10m, 100m, or even larger. The thermal imager can display the image of temperature distribution, and can store the image data in disk or computer, with good effect. But the price of this instrument is relatively expensive, and special personnel shall be responsible for the use and maintenance.