4. High Voltage Electric Appliances for Electric Power
In the operation of high-voltage electrical appliances, sometimes intermittent mechanical stress, tension, pressure, torsion, as well as the role of atmospheric overvoltage and internal overvoltage, therefore, the insulation materials used should be compact, stable to air and humidity, low discharge under rated working voltage, and have high electrical breakdown, arc resistance and mechanical strength.
In modern high-voltage and ultra-high-voltage circuit breakers and complete sets of electrical appliances, the so-called "fully insulated" (fully sealed) system of sulfur hexafluoride is adopted. In this insulating system, the suitable insulating materials are: hot-pressing products impregnated with epoxy resin (liquid) by polyvinegar fibers, epoxy resin casting without filling, and insulating parts and components of polytetrafluoroethylene plastics. Can refer to environmental protection heat shrinkable casing
5. High Frequency Electrical Appliances
In high frequency electrical appliances, the problems of electromagnetic induction, capacitive reactance, eddy current and dielectric loss are prominent. In addition, because of its high frequency and high calorific value, the insulator is required to have high electrical breakdown strength, low dielectric loss and stable dielectric constant.
For high-frequency and high-voltage electrical appliances, the dielectric constant should be small, which will not lead to the increase of capacitance. Applicable insulating materials are: polyethylene, cross-linked polyethylene and polytetrafluoroethylene, etc.
6. Low Frequency Electrical Appliances
The insulation performance requirements of low frequency electrical appliances are approximately the same as those of high frequency electrical appliances. But the frequency is low and the calorific value is low. Therefore, simplifying the structure and reducing the size of the insulation system are the main problems.
7. High and Low Voltage Capacitors
The dielectrics in high and low voltage capacitors should not only have good dielectric properties, but also have high dielectric constant, which can produce large capacitance. The suitable insulating materials are organic silicon liquid and polypropylene film.
8. Precision electrician meter only
Because of the high working accuracy of the precision electrical instrument, the resistance of its insulating part should be large, and it can maintain long-term stability without distortion, which is not affected by the changes of air, temperature and humidity. It is appropriate to use silicone liquid, silicone resin, epoxy resin and other insulation.
9. High Voltage Cable
In high voltage cables, the breakdown strength of insulators should be high and the dielectric loss should be small. In addition, in order to solve the problem of capacitance, the dielectric constant of insulating system should be as small as possible. Therefore, the use of cross-linked polyethylene and Sulfur Hexafluoride as insulation for newly developed high voltage power cables is increasing.
10. High Voltage Insulators
High voltage insulators should have sufficient tensile and tensile strength, and the deterioration rate should be low in outdoor long-term use (the annual deterioration rate should be less than a few thousandths), and the height of poles and towers can be reduced and the span can be increased (in order to reduce the cost of construction and maintenance of lines). In order to meet these requirements, alicyclic epoxy resin composite insulators are used while developing high strength ceramic insulators.
Generally speaking, the performance and quality of various insulation materials should not only meet the basic requirements of the above types of motors and electrical appliances, but also:
(1) It has certain dielectric, physical and chemical properties and mechanical strength under the prescribed heat-resistant grade.
(2) It can meet the needs of different places of use or special regulations, such as plateau, high temperature, high humidity or underwater, tropical, underground, anticorrosive gases, and atomic radiation protection.