Development trends regarding improvements of porcelain insulators

Design of high voltage insulators has always been restricted by a limited choice of materials and closely linked to development of manufacturing processes. Introducing new designs has often been complicated. Time required for engineering, preparation and new tools, has made uniformity desirable, sometimes generating rigid obedience of recommendations. The insulator of porcelain, predominant for more than a century, has been exposed to newborn interests in design and production. This has brought forth the refined conception of contemporary porcelain insulators, CPI. Recently two improvements have received special attention. Isostatic process. Although used to produce high voltage insulators since the 1960´s, it endured until this decade before the complete range of advantages was adopted. Short lead-time, tight tolerances and flexible design have been exploited lately. K-value, the correct calculation of pollution performance. Creepage distance, the fundamental parameter, is easily and frequently calculated and standardized. The recognized fact, that surface resistance for currents are depending on form, not distance, has gone largely unnoticed. The complicity of a formula including circumference and length along varying profiles explains the prevailing status. However, up to date engineering can comprehend calculations impossible in the past. Pollution performance can now be optimized without sacrificing conventional recommendations