Power cables electric field strength across

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 to RAC CABLE  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 shows that the insulation resistance decreased with increasing temperature coefficient of the exponential type, while the conductivity increases exponentially with the temperature increase of the power cable type encountered when the electric field strength at low electric field strength within the range of the ion migration increases with increasing field strength , proportional to the ion current and the electric field strength obey Ohm's law , when the electric field intensity is relatively high, with the increase of the ion mobility and electric field intensity is gradually increased from the linear trend becomes exponential , when there will be a lot closer to the breakdown of the electron mobility , then greatly reduce the insulation resistance coefficient . 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 when the electric field of the insulation resistance coefficient obviously reflects out. Effect of humidity due to the small conductance large, and the water molecules of the polymer molecule size much smaller than that in the thermal effect of the relative motion of the polymer chain composed of macromolecules  HDMI CABLE and section within easy infiltration of water molecules on the polymer , so that an increase in the ionic conductivity of polymer , leaving the insulation resistance decreases. 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 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 .