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UNIT 12
7 MOST KNOWN HIGH VOLTAGE
INSULATION METHODS

1 Learn the meaning of the following words, word-
combinations and word groups:
Homogeneous, dielectric constant, electric field strength gradient,
air pockets, corona, localized arcing, implications range, rapid
insulation failure, encapsulant, homogeneity, derate, insulator
thickness, insulator homogeneity, equation, relationship between
thickness and dielectric strength, hermetically sealed, poisonous
gasses, arc, hazardous, suffocation, odorless gas, undetected,
avoid inhalation, epoxy, adhesion, potting process, damage,
thermal stresses, unrepairable, be discarded.

2 Read and translate Text 1:

Text 1
7 Most Known High Voltage Insulation Methods

Homogeneous characteristics
Before getting to the specifics of each material, there are a
couple of issues that apply to all materials. First, it is important
that the insulating material is homogeneous. This is to ensure that
the dielectric constant is the same throughout so that the electric
field strength gradient is as constant as practical.
Also, if there are any air pockets, there could be corona or
localized arcing. The implications range from rapid insulation
failure, to gradual, long term degradation. Thus, it’s a good idea to
include a method for removing air from any encapsulant.
One implication of homogeneity is that it is generally not a
good idea to use more than one insulation material. Putting two
materials “in series” can do more harm than good.
Second, it is important to derate the insulation’s dielectric
strength, often expressed in volts per mil (a volt per mil (V/mil) is
the non-SI unit of the strength of the electric field. The strength of
1 V/mil is achieved if a voltage of 1 V is applied between two
infinite parallel planes spaced 1 mil apart. 1 V/in = 39370.1 V/m =
1000 V/inch. Mil is the unit of length. 1 mil = 1/1000 of an inch.).

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