We all know that the insulation of wires and cables will affect their resistance. So, what are the factors that affect cable insulation? Follow the editor to find out!
What are the influencing factors of cable insulation
1. The influence of temperature
As the temperature increases, theAAAC cable insulation resistivity decreases. This is due to the increase in thermal movement and the increase in ion generation and migration. Under the action of voltage, the conduction current formed by ion movement increases and the insulation resistance decreases.
Theory and practice show that the insulation resistivity decreases exponentially with the increase of temperature, and the conductivity increases exponentially with the increase of temperature.
2. The influence of electric field strength
When the electric field intensity is in a relatively low range, the mobility of ions increases in a proportional relationship with the increase of the electric field intensity. The ion current and electric field strength follow Ohm's law. When the electric field intensity is relatively high, as the electric field intensity increases, the ion mobility gradually changes from a linear relationship to an exponential relationship. When the electric field intensity is close to breakdown, a large amount of electron migration will occur, and the insulation resistivity will be greatly reduced.
The withstand voltage test voltage of various wire and cable products specified in the standard is in the stage where the ion mobility increases proportionally to the electric field strength, so the influence of the electric field strength on the insulation resistivity cannot be reflected. When the sample is subjected to the breakdown test, the influence of the electric field on the insulation resistivity is clearly reflected.
3. The influence of humidity
Due to the large 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 chain links move relatively, so that water molecules can easily penetrate into the polymer and increase polymerization. The conductive ions in the material reduce the insulation resistance.
This ACSR standardspecifies the immersion test of various wires and cables. For example, before measuring the insulation resistance, the rubber test piece is soaked in water for 24 hours. The purpose is to meet the influence of moisture and water on electrical performance during use.
Insulation resistance is one of the main electrical properties of insulating materials and an important indicator of wire and cable products or materials. Generally, the insulation resistance is not lower than a certain value. If the insulation resistance value is too low, the leakage current along the wires and cables will inevitably increase, resulting in waste of electric energy. At the same time, electrical energy will turn into thermal energy, preparing for thermal breakdown and increasing the possibility of thermal breakdown.
4. The influence of material purity
Impurities are mixed into the material, increasing the conductive particles in the material and reducing the insulation resistance. Therefore, the insulation resistance of a certain rubber and plastic material will reflect the purity of the material and verify whether it meets the standard.
During the wire and cable production process, the process does not strictly comply with the operating procedures, mixed impurities and materials are blistered due to moisture, the insulation core deviation or outer diameter is smaller than the standard, the insulation layer or cracks, and the insulation scratches. , 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. During the use of wires and cables, measuring the change in insulation resistance can also check insulation damage and prevent accidents.