HIgh Voltage Insulators: Liquids

Oil is commonly used in high voltage transformers and high power systems due to its excellent thermal conductivity, which can be improved further by circulation. Handling oil can be messy, and there can be environmental regulations to deal with if large quantities are used. One common type is manufactured by Shell.

Silicone oil is another good liquid insulator. In addition, silicone heat transfer fluids such as Dow Corning Syltherm™ can also be used as high voltage insulators.

Perfluorinated liquids such as Fluorinert™ are clean and easy to use. They are great insulators and can be used for testing high voltage circuits before they are potted. However, they are expensive, some types evaporate quickly.

High Voltage Capacitors

What makes a capacitor identifies as "high voltage" is a rating above 2kV. That's because there are many manufacturers that build capacitors rated up to 1600V or 2000V. (This is in accordance with my definition of high voltage, "High voltage starts at the point where designers have to consider additional technical issues, and where there are significantly fewer component suppliers to choose from. " Typical dielectrics used for high voltage capacitors include ceramic, polyester and mica. Issues that become more important at higher voltages that affect performance and reliability include capacitor construction (and how it affects the electric field), voltage coefficient, creepage distance along the surface, surge current capability (during an arc) and compatibility with potting compounds. See this list of high voltage capacitor manufacturers.

What is High Voltage?

A good place to start is to define high voltage. There is no universally accepted definition. So, here's a list of high voltage definitions to select from!

Related is this high voltage glossary, which can come in handy now and then.