Electric strength of solid insulation

    As we all know, the electrical strength of solid insulation is far greater than the electrical strength of air; the insulation distance through solid insulation materials is usually much smaller than the electrical gap, resulting in high electrical stress; in an insulation system, there are different insulation layers between the electrode and the insulation. There may be gaps between them, or the insulating material itself has air gaps. In these gaps or air gaps, when the voltage is far below the breakdown level, partial discharge may still occur, which will affect the service life of the solid insulation. When the peak voltage is less than 500 V, partial discharge is generally unlikely to occur.

    Compared with gas, solid insulation is not a recoverable insulation medium, and it may have a destructive effect on solid insulation when high-voltage peaks occasionally occur. This situation will occur in daily use and routine high-voltage tests.

    Many adverse effects, such as electrical stress and other stresses (e.g., heat, environment), will accumulate during the service life of the solid insulation, thereby forming a complicated process and eventually leading to insulation degradation.

    The long-term performance of solid insulation can be simulated by short-term tests combined with appropriate conditions.

    If the solid insulation is subjected to high frequency, the dielectric loss and partial discharge of the solid insulation will increase. This situation can be observed in the switching power supply where the insulating material repeatedly bears the peak voltage at a frequency to 500 kHz.

    There is a certain connection between the thickness of solid insulation and the failure mechanism described earlier. When the thickness of the solid insulation decreases, the electric field strength increases, and the risk of failure also increases. Since it is impossible to calculate the required thickness of solid insulation, the performance can only be verified through tests.

(Huiputech)