Electrical workers often need to use insulation resistance tester in their work. The main function of the device is to test the insulation resistance of transformers, transformers, generators, high-voltage motors, power capacitors, power cables, lightning arresters, etc. It has the characteristics of convenient use and high precision. But when many people use it for the first time, sometimes it's hard to get the results. What are the factors that affect the accuracy of insulation resistance tester?
In general, the resistance through the material decreases with increasing temperature and humidity in the environment. In contrast to the enterprise, surface resistance (rate) is sensitive to environmental and humidity data, while body resistance (rate) is sensitive to temperature changes. Humidity can increase, surface information leakage increases, and volume conductance current also increases. With the increase of temperature, the development rate of carrier motion accelerates, and the absorption current and conductance current of different materials in the medium will increase accordingly. According to relevant research literature, the resistance value of the general working medium at 70C is only 10% of that at 20C. Therefore, when measuring the resistance of technical materials, it is necessary to show that the temperature and humidity of the sample and the environment are in balance.
The resistance value of a dielectric material cannot remain constant over a wide voltage range, that is, Ohm's law does not apply to it. At room temperature, in the lower voltage range, the conductance current increases linearly as the applied voltage increases, and the resistance value of the material remains constant. Beyond a certain voltage, the conductance current increases much faster than the test voltage, and the resistance value of the material decreases rapidly. It can be seen that the higher the test voltage applied, the lower the resistance value of the material, so the resistance value of the material tested at different voltages may be quite different.
It is important to note that changes in the resistivity of the material result in the strength of the electric field being measured, not the voltage being tested. If the distance between electrodes is different for the same test voltage, the test result of material resistivity will be different. The smaller the distance between positive and negative electrodes, the smaller the test value.
When the measured pressure is equal to the DC voltage of a material, the current of the material under test is an unstable instantaneous value, but there is a decay process. When pressurized, a large charging current flows, and then a relatively long absorption current slowly decreases, and then a relatively stable conduction current is reached. The higher the measured resistance, the longer it takes to reach equilibrium. Thus, when the resistance value is measured and read correctly, the measured resistance value is the value that is read after a stable or pressure reading is obtained one minute later.
In addition, the resistance values of highly insulating structural materials are related to the historical development of electrification. In order to accurately analyze and evaluate the electrostatic properties of the materials studied, when the resistance (rate) of the building materials can be tested, the first treatment should be carried out to eliminate electricity, stand for a certain time, which may take 5 minutes, and then design and test according to the measurement system procedures. Generally speaking, when testing a learning material, at least 3-5 samples should be randomly selected for quality management test, and the average value is taken as the main test result.
There are still many problems to pay attention to when using an insulation resistance tester.
Wuhan Xinshengneng Technology Co., Ltd. is a professional insulation resistance equipment manufacturer, not only produces all kinds of power testing equipment, and professional technical team to provide all kinds of test technical services, more products more models to choose from, welcome to call 0312-31688565 details!
