Treść książki
Przejdź do opcji czytnikaPrzejdź do nawigacjiPrzejdź do informacjiPrzejdź do stopki
locationrelativetotheelectrodes,thesurfaceofthegasinclusion,andthetypeofsolid
dielectricmaterial.
DETERMINISTICANDSTOCHASTICDISCHARGEMODELS
Theabovegeneraldescriptionofthedischargemechanismreferstoeitherthedeter-
ministicorstochasticmodel(asshowninFigure3.6).Inadeterministicmodel,thefol-
lowingassumptionsarevalid:
UciandUce=const
δUc,δUa,qc,qa=const
Uci
+=U
ci
–andU
ce
+=U
ce
–
Inthismodel,thenumberofdischargeimpulsesinbothhalvesoftheperiodandin
thesuccessiveperiodsisconstant:
N
+=N–
N=N
++N–,
andthechargesofthesuccessivedischargesareidentical:q1=q2=qi.
Inastochasticmodel,thePDinceptionandextinctionvoltagearevariable,asare
thederivedparameters(Fig.3.6b):
UciandUce=var
δU,ΔU,q=var
Uci
+≠U
ci
–andU
ce
+≠U
ce
–
N
+≠N–
q1≠q2≠q3≠,...,qn
Thefirstmodelofapartialdischargemechanism(presentedaboveinFigure3.4)
wasintroducedbyGemantandPhilipphoff[GEMA32]nearlyacenturyago.Originally,
theyinvestigatedpowerlossesinmassimpregnatedpowercablescausedbydischarges
incavities.ThisapproachwasfurthermodifiedbyWhiteheadandKreugerinthe1950s
[KREU89].Inthismodel,theexternaldetectablecharge(commonlycalledtheappar-
entcharge)issmaller(Equation(3.9))thantherealchargerelatedtotheplaceofdis-
charge(whichcannotbemeasureddirectly).TheIEC60270standard[SIEC270]is
basedonthisconcept.Someresearchers[HAUS14,PEDE89]challengethisconcept,
arguingthattheradiusofthedischargechannelshouldbeassumedinsteadofcapaci-
tanceCcbeingdeterminedbyavoid,sshape.
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