Dielectric Strength Tests

Dielectric Strength Tests

In physics, the term dielectric force has the following meanings:

The maximum electric field from the insulating material that a pure material can withstand under ideal conditions without deterioration (ie, failure of the insulating properties).
The minimum applied electric field (ie, the applied voltage is divided by the electrode separation distance) for a specific configuration of the dielectric material and the electrodes, resulting in failure. This is the concept of Fault voltage.
The theoretical dielectric strength of a material is a property inherent in the bulk material and is independent of the configuration of the electrodes to which the material or field is applied. This & quot; cored dielectric strength & quot; corresponds to that to be measured using pure materials under ideal laboratory conditions. In the event of a fault, the electric field releases the connected electrons. If the applied electric field is high enough, the free electrons exposed to background radiation can reach speeds that can release additional electrons during collisions with neutral atoms or molecules in a process called avalanche breakdown. The fault occurs very quickly (usually in nanoseconds) and forms an electrically conductive path and a disturbing discharge through the material. For solids, a failure event significantly reduces or even destroys the insulation capability.

Factors affecting apparent dielectric strength

as the sample thickness increases.
decreases as the operating temperature increases.
decreases with increasing frequency.
Gases (eg nitrogen, sulfur hexafluoride) are normally reduced with increasing humidity.
For air, the dielectric strength increases slightly as absolute humidity increases, but decreases with increasing relative humidity.

Fracture field strength
The field strength at which the disintegration occurs depends on the geometry of the electrodes to which the dielectric (insulator) and the electric field are applied, as well as the speed at which the electric field is applied. Since dielectric materials generally contain minor defects, practical dielectric strength will ideally be a fraction of the intrinsic dielectric strength of a flawless material. Dielectric films exhibit greater dielectric strength than thicker samples of the same material. For example, the dielectric strength of silicon dioxide films having a thickness of several hundred nm to several umm is about 0.5GV / m. However, very thin layers (below, for example, 100 nm) become partially conductive due to electron tunneling. Multilayer thin dielectric films are used, where maximum practical dielectric strength is required, such as high voltage capacitors and pulse transformers. The dielectric strength of gases varies depending on the shape and configuration of the electrodes, usually Nitrogen gas is measured as a fraction of dielectric strength.

Dielectric strength of various common materials (in MV / m or 106 Volt / meter):



Dielektrik Mukavemet (MV / m)

Helyum   ( göreceli için azot )




alüminyum oksit


pencere   bardak

9,8 - 13,8

borosilikat bardak

20 - 40

Silikon yağ ,   maden oi







19 - 160

Neopren   silgi

15.7 - 26.7

damıtık   Su

65 - 70

Yüksek   vakum   ( alan emisyon sınırlı )

20-40 (elektrot bağlıdır şekli )

Sigortalı silis

20'de 25-40   ° C

mumlu kâğıt

40 - 60

PTFE   (Teflon,   ekstrüde   )


PTFE   (Teflon, izolasyon filmi)

60 - 173









In SI, the unit of dielectric force is in volts per meter (V / m). It is also very common to see related units such as centimeters (V / cm) volts and megavolts per meter (MV / m).

Our laboratory performs EUROLAB dielectric strength test services as accredited.