19—8.
TRANSITION REGIONS
447
'
parafned wood
is satisfactory. The wood should be well dried
_
bo11ed gently in paraîn for several days, until, on sect10n1ng, 1t IS found that the parain has completely penetraœd
the wood: Large leakage occurs with ordinary wood due to the
m013ture inside and on the surface.
The ionization of the air in small
—
-
%
closed spaces inside of insulators is often
the seat of an early break down.
These are removed by oil impregnation
WALL
/
'
"
_
under high pressure. .
19—8.
Transition Regions—The
most important simple rule to prevent
5
c
'
break down is
to keep the electrical
Frc.19—5. A bushing.
eld away from those regions in which
»
the structural materials change, as in bushings, metal to glass
,
,
joints or wherever the dielectric constant changes.
’
High voltage bus‘hings are frequently provided with a metal
tube tting snugly into the insulator, as at 1 in gure 19—5. The
tube forms an equi—potential surface and distributes the eld
uniformly through the dielectric, as at B. With—
A
tube (C), the insulation
down
-
in the regions where the eld is concentrated. …
_
‘
Consider two charged metal plates hear and
_
B
parallel to each other.
uniform dielectrie such“ as air between them,
'
+
increases lineay fr0m the negative _to
the, pos2
'
itive plate,—ras at 1%
If one adds
_
_
a slab of ‘in‘sulatihgr material ’ Of‘ , greater
'
break
’
down "strength,_ such
glass '(Shaded‘ _-area),
’
+
With the linterition« »of. …prevehting & rupture,
_
'
@B - he= altëfsÏ_ thpttlgdteidà‘raëæ:
‘.
slty,asatBUnderthe1ncreasedelectrical
'
Fî°-.19-6«.P9êential stresstheairmaybecomemmædThema
,
'
'
wellbepunctufed
:
.
‘
::îa;;:::a;»g;;:e
=
_
:
—
TRANSITION REGIONS
447
'
parafned wood
is satisfactory. The wood should be well dried
_
bo11ed gently in paraîn for several days, until, on sect10n1ng, 1t IS found that the parain has completely penetraœd
the wood: Large leakage occurs with ordinary wood due to the
m013ture inside and on the surface.
The ionization of the air in small
—
-
%
closed spaces inside of insulators is often
the seat of an early break down.
These are removed by oil impregnation
WALL
/
'
"
_
under high pressure. .
19—8.
Transition Regions—The
most important simple rule to prevent
5
c
'
break down is
to keep the electrical
Frc.19—5. A bushing.
eld away from those regions in which
»
the structural materials change, as in bushings, metal to glass
,
,
joints or wherever the dielectric constant changes.
’
High voltage bus‘hings are frequently provided with a metal
tube tting snugly into the insulator, as at 1 in gure 19—5. The
tube forms an equi—potential surface and distributes the eld
uniformly through the dielectric, as at B. With—
A
tube (C), the insulation
down
-
in the regions where the eld is concentrated. …
_
‘
Consider two charged metal plates hear and
_
B
parallel to each other.
uniform dielectrie such“ as air between them,
'
+
increases lineay fr0m the negative _to
the, pos2
'
itive plate,—ras at 1%
If one adds
_
_
a slab of ‘in‘sulatihgr material ’ Of‘ , greater
'
break
’
down "strength,_ such
glass '(Shaded‘ _-area),
’
+
With the linterition« »of. …prevehting & rupture,
_
'
@B - he= altëfsÏ_ thpttlgdteidà‘raëæ:
‘.
slty,asatBUnderthe1ncreasedelectrical
'
Fî°-.19-6«.P9êential stresstheairmaybecomemmædThema
,
'
'
wellbepunctufed
:
.
‘
::îa;;:::a;»g;;:e
=
_
:
—