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Factors affecting the insulation resistance of wires and cables

May 24, 2020

Wire and cable in use, its insulation resistance value is not constant, the impact of wire and cable insulation resistance value of many factors, including four factors are the biggest impact, we will understand these points, to ensure that our wire and cable can avoid these factors to operate normally.

❶Temperature effect                                                     

As the temperature increases, the insulation resistance coefficient decreases.This is due to an increase in thermal motion, the generation and migration of ions.Under the action of voltage, the conduction current formed by the ion movement increases and the insulation resistance decreases. Therefore, when in use, we should try our best to let the wire and cable avoid the heat source. When the home installs the wire and runs through the tube, we should also ensure that there is enough space to send out heat

❷The influence of electric field intensity                             

When the electric field intensity is in a relatively low range, the ionic mobility increases proportionally with the increase of the electric field intensity.The ionic current and electric field intensity follow ohm's law.When the electric field intensity is relatively high, with the increase of the electric field intensity, the ionic mobility gradually changes from a linear relationship to an exponential one.When the electric field intensity approaches the breakdown, a large amount of electron migration will occur, and the insulation resistance coefficient will be greatly reduced.

❸Influence of humidity

Due to the great conductivity of water, the size of water molecules is much smaller than that of polymer molecules. Under the action of heat, polymer macromolecules and constituent chains move relatively, making water molecules can easily permeate into the polymer, increasing the conductive ions in the polymer and reducing the insulation resistance.

❹The effect of material purity

Impurities in the material increase the conductive particles in the material and reduce the insulation resistance.Therefore, to a certain extent the insulation resistance reflects the purity of the material and verifies whether it meets the standard.In the production process of electric wire and cable, the process does not strictly follow the operating rules, the mixed impurities and materials are affected by damp and foaming, the deviation of insulation core or the outside diameter size is less than the standard, the insulation layer or crack, the insulation scratch, etc.Will reduce the insulation resistance of the product.Therefore, in order to check the insulation resistance, it is necessary to check whether there are any problems in the process operation.In the use of electric wires and cables, measuring the change of insulation resistance can also check the insulation damage to prevent accidents