The main factors affecting the resistance of the cable insulation

Wire and cable products for the insulation resistance of the cable insulation is mainly measured volume resistivity , surface resistivity measurements are not , and factors affecting the high-voltage cable insulation resistance value more, in practice there are four main factors greater impact on the insulation resistance coefficient . Temperature of the temperature rise , the insulation resistance coefficient decreased , which is due  hdmi wall plate to increased thermal motion , and the migration of ions produced has increased , the role of the voltage , the conduction current is formed by the ion motion is increased, and thus the insulation resistance drops . Theory and practice show that the insulation resistance coefficient decreased exponentially with increasing temperature type, and then while pressing the conductance increases exponentially with increasing temperature .
Electric field strength across the power cable when the electric field intensity in a range of relatively low mobility of ions increases with increasing electric field strength , is proportional to the ion current and the electric field strength obey Ohm's law , when the electric field intensity is relatively high, ion mobility increases with increasing electric field strength and the linear trend of gradually becomes exponential relationship , the breakdown will occur when approaching a large electron mobility , then the coefficient of the insulation resistance is greatly reduced . Withstand test voltage specified in the standard variety of wire and cable products for the mobility of ions in an electric field intensity increases in proportion with the stage , so the impact of the electric field strength of the insulation resistance coefficient reflects not come out , when do puncture test specimen samples , the influence of the electric resistivity of the insulation obviously reflected in the film due to the small conductance humidity large, and the size of the water molecule much smaller than the polymer molecules, macromolecules and polymers in the composition under heat link relative movement of water into the polymer molecules within easy , increasing the inner ion conductive polymer , leaving the insulation resistance drops . Standard provides a variety of water immersion test wire and cable , such as rubber specimen measuring insulation resistance before soaking for 24 hours, because its purpose is to be  Terminal BLOCK encountered in the use of water on the influence of moisture and electrical performance . Insulation resistance is one of the main electrical performance insulation materials, wire and cable is an important indicator of a product or material , generally require insulation resistance of not less than a certain value. If the insulation resistance value is too low, the line along the wire cable must increase the leakage current , resulting in waste of energy , and electrical energy into heat energy , the thermal breakdown preparation conditions , increase the possibility of thermal breakdown . DC cable insulation , you can also make use of the material composition of the different phases resistivity insulation to improve material utilization , improve the surface resistivity of the cable insulation is also very important , when the surface dirt and moisture , because of its distribution is not uniform, so that part of the surface may be exposed to high voltages, which leads to partial discharge or creeping discharge aluminum cable , causing catastrophic failure , but may also reduce the surface resistance of artificial means , such as a conductive core of the cable , because the surface is not completely smooth uneven distribution of the electric field causes the electric field strength will be higher corona discharge wire in the conductive rubber core coated with a conductive or semi- conductive the surface of the plastic core is reduced to eliminate the corona field intensity , and, according to the insulation material coefficient of variation of the resistance to determine the degree of moisture of the material. Mixed material impurities affect the purity of the material , increasing the material conductive particles , the insulation resistance drops , so some kind of rubber and plastic materials will reflect the size of the insulation resistance of the material purity level , to verify their compliance with standards, wire and cable in the production process , the process is not strictly abide by the rules , mixing impurities, moisture and foaming material , insulation or partial core diameter size smaller than standard insulation delamination or cracks , scratches and other insulation will make products, insulation resistance decreases, so check the insulation resistance be sure to check whether there is a problem in the process of process operation , in the course of the wire and cable , measure the insulation resistance changes can also check the insulation damage , prevention of accidents.