Dielectric Gels and Insulator Fluids: Operation and Applications

Dielectric greases and insulator fluids include oils, gels, and fluids applied to electrical terminals in high-voltage equipment. Their main functions are preventing or minimizing electrical discharges, and insulating and lubricating rubber gaskets and surfaces. Plus preventing moisture permeation and dissipation of heat.

Operation

Dielectric insulator gels and insulation fluids seal and lubricate the nonconductive mating surfaces of electrical connections. Due to their high resistivity, these fluids mitigate arcing when an electrical current is present. Dielectric fluids need to exhibit superior thermal stability and heat transfer, while still staying noncorrosive. Combustion resistance and low toxicity are a couple of other beneficial properties. However, a little risk is often accepted on account of costs and application.

The gel preserves uniform resistance after a corona or arc. However, extended breakdowns can create impurities and conductive pathways. Electrically induced corrosion between electrical connections of dissimilar metals may be prevented with a dielectric gel between high-pressure contacts, but will also weaken low-pressure contacts.

Some gels may act as a solvent when they come in contact with system components, like gaskets, O-rings, seals; or filters that contain reactive rubber or plastics. Different additives to most dielectric gels can customize utility to a specific application.

Applications

General: Various applications benefit from the inclusion of a liquid dielectric material. Gel-filled and gel-impregnated capacitors are commonly used in a variety of high-current and high-voltage applications, including motor-run, motor-start, and power factor correction. They are furthermore used in switchgear for quenching arcs when contacts are disconnected.

Transformer Fluids: Transformer fluids are used in specific types of power transformers. The fluid is often managed by radiators, filters, fans, pumps, or heat exchangers. And regular testing is conducted to ascertain when it needs to be replaced. Mineral oils are the most common, but synthetic esters and silicone-based dielectric insulator fluids are also rising in popularity.

Electric Discharge Machining (EDM) Fluid: EDM is a metal-forming process where particles of the workpiece are eroded by recurrent discharges between two electrodes. EDM fluids act as semiconductors to generate a stable spark-induced ionization between the electrodes, in addition to rinsing debris away. The dielectric gel has a specific voltage and amperage, however, with recurrent use, the EDM fluid may degrade.

Petroleum-based EDM fluids are inexpensive and used extensively, but have a short service life—on average 5 years. Synthetic EDM fluids rarely degrade in dielectric strength, leading to a long service life. They are less toxic to employees but are more expensive. Plant-based EDM gels are used especially in the healthcare sector, where equipment cannot be exposed to petroleum or synthetic types.

The following parameters may be considered when choosing a dielectric insulator gel:

Viscosity: It is the flow characteristics of a liquid. In relation to dielectric liquids manufacturers will determine a value measured in centistrokes (cST) or Saybolt Universal Seconds (SUS). Lower values signify a thinner, less viscous fluid.

Dielectric strength: The highest value the dielectric can easily accommodate. This is identified as MV/m or V/mil.

Breakdown voltage: The lowest voltage that compromises the insulative properties of the dielectric.

Conclusion

This is all about the operation and applications of dielectric gels.