Physical fundamentals of insulation design for low-voltage equipment

Insulation coordination for low-voltage equipment has been an important concern of several international committees. The reports 664 and 664A of the International Electrical Commission (IEC) gave the basis for thorough investigations in 1980 and 1981. About 30000 insulators have been observed for several years under various voltages. Insulation resistance and electrical strength were measured and have provided ≈10⁶ data points. These results were evaluating using statistical methods. In addition, a research program was carried out to quantify the influence of insulating materials, environmental conditions, and the design of the insulating systems on the long-term insulation behavior. The final results are intended to support the drafting of scientifically founded, revised standards on insulation coordination in the IEC