Treść książki
Przejdź do opcji czytnikaPrzejdź do nawigacjiPrzejdź do informacjiPrzejdź do stopki
(eachwithathicknessofd1).Thegeometricalrepresentationofthespecimenisillus-
tratedinFigure3.10andcorrespondstothemodelshowninFigure3.8.
Assumingthedielectricrelativepermittivityandresistivityoflayers
–εg,pgofglassplate(layer0),
–ε1,p1oftop/bottomcavityflake(layer1),
–ε2,p2ofvoidlayer(layer2)
aswellastheabove-mentionedgeometry,theapproximatepartialdischargeinception
voltage(PDIV)thresholdsonthespecimenterminalscanbeestimatedforbothAC
(Uinc_AC)andDC(Uinc_DC)cases.
Fig030100Specimengeometryandnotation:ε–dielectricrelativepermittivity;
p–electricresistivity;d–thickness;D–voiddiameter(explanationintext)
ThefollowingequationreflectstheACcase,takingintoaccountthematerialper-
mittivityandthethicknessoftheinsulatinglayer(assumingthattherelativepermittivity
oftheairequalsone):
U
inc
_AC
=
⎛
⎜
⎜
⎝
2
ε
d
g
0
+
2
ε
d
1
1
+
d
2
⎞
⎟
⎟
⎠
⋅
E
p
(3.23)
ForDC,casematerialresistivityandlayerthicknessareconsidered:
U
inc
_DC
=
⎛
⎜
⎝
2
p
p
2
g
d
0
+
2
p
p
2
1
d
1
+
d
2
⎞
⎟
⎠
⋅
E
p
(3.24)
AtDCvoltage,insulatingmaterialconductivityrevealsastrongtemperaturede-
pendence,whichisnotconsideredinthischapter.Hence,temperaturehasastrong
effectatDCvoltageonelectricfielddistributionandtherelatedchargingstagewith
recoveryvoltagebuild-up,includinganinfluenceonthePDdynamics[GU19].The
measurementswereperformedatroomtemperature.
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