绝缘件结构设计主要是保证两导电体间的绝缘间隙（即两导电零件之间最短的空间距离）和爬电距离（即两导电零件之间沿绝缘体表面的最短距离）足够承受所要求的耐电压值。一般来讲，影响绝缘间隙的主要因素有：瞬时过电压、电场条件（即导电零件的形状）、污染情况和海拔高度等；影响爬电距离的主要因素有：绝缘耐电压、工作电压、污染（其程度取决于温度、爬电距离的方向和位置、绝缘表面形状、静电沉积）、绝缘材料性能、同间隙的关系（爬电距离不能小于有关间隙，有可能最短爬电距离就等于间隙）、承受电压的时间以及其他因素。当导电零件间的绝缘间隙足够大时，可以有效地限制瞬时过电压的危害，因为绝缘间隙足够大时瞬时，过电压虽产生飞弧，但仍不足以电离绝缘间隙。导电零件间漏电流的大小取决于持续工作电压的有效值或直流值，所以爬电距离的大小就限制了持续工作的电压大小。

Insulation parts structure design is to ensure that the insulation between two conductive clearance (that is, the shortest distance between two conductive parts) and the creepage distance (i.e., the shortest distance between two conductive parts along the insulator surface) enough to bear the required voltage resistance value. Generally speaking, the main factors that influence the interstitial space are transient overvoltage, electric field conditions (the shape of the conductive parts), pollution and elevation, etc. The main factors influencing the creepage distance: insulation resistance to voltage and working voltage, pollution (it depends on the temperature, the direction of the creepage distance and location, insulation surface shape and electrostatic deposition), insulation performance, relationship with clearance, creepage distance is not less than the gap, shortest possible creepage distance equals clearance), withstand voltage, time and other factors. When the insulation of the gap between the conductive parts is enough big, can effectively limit the harm of transient overvoltage, because insulation clearance enough instantaneous, the arcing overvoltage, though, but still not enough to ionization insulation gap. Conductive parts between the effective value of leakage current depends on the size of the continuous working voltage or dc value, so the size of the creepage distance limits the size of the continuous working voltage.