Intrinsic breakdown, electrical properties

Electric strength is usually taken as the nominal voltage gradient (applied voltage divided by test piece thickness) at which breakdown occurs under specified conditions of test. These specified conditions of test are important as the measured electric strength is not an intrinsic property of the material but depends on test piece thickness, time of electrification and the electrode geometry, as well as on conditioning of the material. 

The theoretical dielectric strength is an intrinsic property of the bulk material and depends on the material composition and also on the configuration of the electrodes with which the field is applied. For a given configm-ation of dielectric material and electrodes, the minimum electric field that produces breakdown is the breakdown voltage in this particular set up the maximum electric stress to the material is just before breakdown. 

---