|Tipler, Paul and Mosca, Gene. Physics For Science and Engineers. Susan Finnemore Brennan, 2004: 768.||
|Dalal, Nikesh and Jamie Rasmussen. Dielectric Strength of Various Material. The Electronics Workshop. thinkquest.org. 1997.||
|Rigden, John S. Macmillan Encyclopedia of Physics. Simon & Schuster, 1996: 418.||
A dielectric is a substance in which an electric field may be maintained with zero or near-zero power dissipation. A dielectric material is an electrical insulator. In a dielectric, electrons are bound to atoms and molecules; hence there are few free electrons. The dielectric strength of a material is an intrinsic property of the bulk material and is not dependent on the configuration of the material or the electrodes with which the field is applied. In a given configuration of dielectric material and electrodes, the minimum electric field that produces breakdown. At breakdown, the electric field frees bound electrons, turning the material into a conductor.
The dielectric strength is normally expressed in volt/mm; the voltage at which the insulator breaks down, divided by the thickness in millimeters.
Measuring the dielectric strength of a material, for example paper, includes the following: (Source: Buckleys URVAL, Ltd.)
- Obtain a sample of paper with a uniform thickness applied to a sheet of metal.
- Connect the Holiday Detector to the sample with the earth lead connected to the metal and the high voltage probe to the surface of the paper.
- Starting with the output voltage set to minimum, slowly increase the volts until the material breaks down and the alarm on the Holiday Detector sounds.
- Lift the HV electrode off the paper and note the output voltage.
- Repeat this test a number of times on a new area of the paper at least 20 mm from where the previous breakdowns have occurred, noting the breakdown voltage each time.
- Take an average and then 75% of that is approximately the dielectric strength of the paper.
The standard dielectric strength for paper is tested to be 16 MV/m.
Vashti Prasad -- 2007