If a voltage is applied for a very short time of the order of 10-8 seconds, the dielectric strength of the specimen increases rapidly to an upper limit known as ______.
intrinsic dielectric strength
Understanding Dielectric Strength Under Short Voltage Application
Dielectric strength is a measure of the electrical insulation capability of a material. It represents the maximum electric field that a material can withstand under specific conditions without breaking down and allowing current to flow.
The breakdown process in dielectric materials is not instantaneous and depends on the duration for which the voltage is applied. Different breakdown mechanisms occur over different timescales.
When a voltage is applied for a very short duration, specifically of the order of \(10^{-8}\) seconds or less, slower breakdown mechanisms like thermal breakdown, treeing, tracking, or electromechanical stress do not have enough time to develop. Breakdown under such rapid application is primarily due to electronic processes within the material.
This rapid breakdown, governed by the material's atomic and molecular structure and the behavior of free electrons, leads to what is known as intrinsic dielectric strength. It is considered the theoretical upper limit of the dielectric strength for a pure material under ideal conditions, as it avoids the influence of defects, impurities, and slower degradation processes.
Therefore, if a voltage is applied for a very short time of the order of \(10^{-8}\) seconds, the dielectric strength of the specimen increases rapidly to an upper limit known as intrinsic dielectric strength.
- Electromechanical breakdown: Occurs due to deformation under electrical stress, typically a slower process.
- Breakdown due to treeing and tracking: These are surface or internal degradation paths forming over time, much longer than \(10^{-8}\) s.
- Thermal breakdown: Involves heating and thermal instability, also a slower process requiring time for heat to generate and accumulate.
- Intrinsic dielectric strength: The breakdown limit determined by the material's fundamental electronic structure, reached under rapid field application.
Considering the very short time scale mentioned (\(10^{-8}\) seconds), the breakdown mechanism involved is intrinsic breakdown.
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