The so-called insulation is a safety measure that uses non-conductive substances to isolate or wrap the charged body to protect against electric shock. Good insulation is the most basic and most reliable means to ensure the safe operation of electrical equipment and lines and prevent personal electric shock accidents. Insulation can usually be divided into three categories: gas insulation, liquid insulation and solid insulation. In practical applications, solid insulation is still the most widely used and most reliable insulating material.
Under the action of strong electricity, the insulating material may be broken down and lose its insulating properties. Among the above three kinds of insulating materials, after the gas insulating material is broken down, it can recover its inherent electrical insulating properties by itself once the external factors (strong electric field) are removed; while the solid insulating material is completely lost irreversibly after being broken down. its electrical insulating properties. Therefore, the insulation selection of electrical lines and equipment must be matched with the voltage level, and must be adapted to the use environment and operating conditions to ensure the safety of the insulation.
In addition, due to corrosive gases, vapors, moisture, conductive dust and mechanical operations, etc., the insulating properties of insulating materials may be reduced or even destroyed. Moreover, the long-term effects of environmental factors such as sunlight, wind and rain can also cause the aging of insulating materials to gradually lose their insulating properties. In general, the main indicators that affect the performance of insulating materials are as follows. Nuofeng thermal insulation material manufacturers will share with you the following!
- Relative permittivity and dielectric loss tangent
The use of insulating materials is divided into the mutual insulation of various components of the electrical network and the medium (energy storage) of capacitors. The former requires a small relative dielectric constant, the latter requires a large relative dielectric constant, and both require a small dielectric loss tangent, especially for insulating materials used under high frequency and high voltage, in order to make the dielectric loss small, both require the use of Insulating material with small dielectric loss tangent.
- Insulation resistance, resistivity
Resistance is the reciprocal of conductance and resistivity is the resistance per unit volume. The smaller the conductivity of the material, the greater its resistance, and the two have an inverse relationship. For insulating materials, it is always hoped that the resistivity is as high as possible.
- Combustion resistance
The ability of an insulating material to resist burning when it comes into contact with a flame or to prevent continued burning when it leaves the flame. With the increasing application of insulating materials, the requirements for their combustion resistance are more important. People use various means to improve and improve the combustion resistance of insulating materials. The higher the flame resistance, the better its safety.
- Breakdown voltage, electrical strength
Under a certain strong electric field, the insulating material is damaged and loses its insulating properties and becomes a conductive state, which is called breakdown. The voltage at breakdown is called breakdown voltage (dielectric strength). Electric strength is the quotient of the voltage when breakdown occurs under specified conditions and the distance between the two electrodes subjected to the applied voltage, that is, the breakdown voltage per unit thickness. For insulating materials, generally the higher the breakdown voltage and electrical strength, the better.
- Tensile strength
In a tensile test, the maximum tensile stress that the specimen is subjected to. It is the most widely used and most representative test for mechanical properties of insulating materials.
- Arc resistance
The ability of an insulating material to withstand the action of an electric arc along its surface under specified test conditions. In the test, AC high voltage and small current are used, and the arc resistance of the insulating material is judged by the time required to form a conductive layer on the surface of the insulating material by the arc action generated by the high voltage between the two electrodes. The larger the time value, the better the arc resistance.
- Sealing degree
The degree of sealing can be expressed by the volume or mass of the medium leakage per unit time, and the leakage rate. The ideal situation where the sealing volume is zero is called “zero leakage”. Generally speaking, static seals may achieve zero leakage, but for dynamic seals, any relative displacement in contact with the sealing surface will create conditions for the leakage of medium at the rough excess on the joint surface, and it is particularly difficult to achieve zero leakage. In engineering, the allowable value of tightness is often specified for important seals.