NHN insulation paper is a soft composite material with a heat resistance grade of H (180 ℃), which has the advantages of non layering, non foaming, and non adhesive flow. NHN insulation paper is widely used, and the quality of insulation paper on the market varies. What are the factors that affect the resistance value of NHN insulation paper?
1、 The impact of humidity. The surface of NHN insulation paper adsorbs moisture, and a water film forms on the surface of the porcelain sleeve, which often significantly reduces the insulation resistance. When the relative humidity in the air is high, it absorbs more water, increases conductivity, and also reduces the insulation resistance value.
2、 The influence of temperature. The temperature has a significant impact on the resistance of NHN insulation paper, and generally, the insulation resistance decreases with the increase of temperature. The reason is that as the temperature increases, the polarization in the insulation medium intensifies, the conductivity increases, and the insulation resistance value decreases. And it is related to the degree of temperature change and the properties and structure of the insulation material. Therefore, it is necessary to record the temperature during measurement in order to convert it to the same temperature for comparison.
3、 The impact of discharge time. After each insulation test, the tested material should be fully discharged, and the discharge time should be greater than the charging time, in order to fully charge the remaining charge. Otherwise, during the re measurement, due to the influence of charge, the charging current and absorption current will be smaller than the previous measurement, resulting in a false phenomenon of an increase in the insulation resistance value of the absorption ratio. The insulation condition of high-voltage electrical equipment with large capacitance is mainly judged based on the absorption ratio. If there is a significant decrease in absorption ratio, it indicates that the NHN insulation paper is damp or the oil quality is severely deteriorated.