Rated voltageVRated impulse voltageVOvervoltage categoryIIIIII50 and 150 and =300150025004000Clause29Clearances,Creepagedistancesandsolidinsulation爬电距离、电气间隙和绝缘穿通距离(Table1)Minimumclearance(Table2)Rated impulse voltageVMinimum clearancemm3300.55000.58000.515000.525001.540003.060005.580008.0100011.0HowtofindtheminimumclearanceHouseholdapplianceareinovervoltagecategoryIISelecttheratedvoltageUsingthetable1tofindouttheratedimpulsevoltageAccordingtotable2,theminimumclearancecouldbefoundbyratedimpulsevoltageTheclearancesoffourinsulationtypes:1.Basicinsulation2.Supplementaryinsulation3.Reinforcedinsulation4.FunctionalinsulationTheclearanceofbasicinsulationExample 1 : Water kettleRating : 220 240V 50Hz 2500 3000WRated voltageVRated impulse voltage (V)Overvoltage categoryIIIIII150 and 150 and 1mmTubular sheathed heating elementPollution degree 129.1.2clearanceofsupplementinsulationTheminimumclearanceissameasthebasicinsulationThe distance between enclosure and internal wire29.1.3clearanceofreinforcedinsulationThe reinforced insulation using the next step for rated impulse voltage. Between terminal and plastic enclosure29.1.4clearanceoffunctionalinsulationBetween terminalsThe functional insulation is between live parts of different potentialPTCHeatingelementHairstraighterPTCheaterHair straighter assemblyDifferenttypesofPTCHeatingelementsInternalconstructionofPTCheatingelementThe clearance between surfaces of PTC heating elements may be reduced to 1mmThe clearance =1mmKapton filmPTC heating plateElectrode plate29.2creepagedistancesStep 1 (To find out the pollution degree)Pollution degree 2 applies unlessPrecautions have been taken to protect the insulation, in which case pollution 1 appliesThe insulation is subjected to conductive pollution, in which case pollution degree 3 appliesNote: The pollution degree should need refer to part 2. StandardPollution degree60335 2 3II60335 2 9III60335 2 14III60335 2 15 III60335 2 23 II60335 2 80 IIIPollutiondegreeclassificationTracking index (CTI) valuesMaterial group I: 600=CTIMaterial group II: 400=CTIMaterial group III a: 175 =CTI 400Material group III b: 100 =CTI175Step 2 (To find out the material group)TrackingindextesterTrackingindex(CTI)valuesMinimumcreepagedistancesforbasicinsulationWorking voltageVCreepage distance mmPollution degree123Material groupMaterial groupIIIIII a/bIIIIII a/b50 and 125 and 250 and 400 and 500 and 125and=250ThecreepageofbasicinsulationWorking voltageVCreepage distance mmPollution degree123Material groupMaterial groupIIIIII a/bIIIIII a/b50 and 125 and 250 and 400 and 500 and = 8001.83.24.56.38.09.010.0Working voltageVCreepage distance mmPollution degree123Material groupMaterial groupIIIIII a/bIIIIII a/b50 and 125 and 250 and 400 and 500 and = 8001.83.24.56.38.09.010.0MinimumcreepagedistancesforfunctionalinsulationInsulation typeDistanceBasic insulation4Supplementary insulation4Reinforced insulation8Functional insulation3.2SummaryofMinimumcreepagedistances29.2.1creepageforbasicinsulationLacqueredconductorsofwindingsCreepage distance of winding need not be greater than the associated clearance specified in table 16Asperclause29.2.2,thecreepagedistanceofsupplementaryinsulationshallnotlessthanand2.5mm.Theinternalwireofmicro-switchwasnotsecurelyfixedthatitwaspossibletobetouchedbytestfingerwith2Nforce.Thecreepagedistanceweremeasuredas0mmInternalwireshallbeaccessThecreepagedistancesofreinforcedinsulationshallnotlessthan8mm.Asresult,thecreepagedistancewasmeasured7.5mmbetweenleadsofneonlampandthelampcoverjoint.LeadsofneonlampLensEnclosureLeonlampleads2mm3mmThecreepagedistances=2.5+2+329.2.4creepagedistancesoffunctionalinsulationCreepage distance betweenMeasured resultsLimitationSwitch terminals1.5mm2mmDistance betweenMeasured resultsLimitationPCBBetween Point A and BClearanceCreepageClearanceCreepage2.07mm2.75mm1.5mm2.0mmPCBTrackABBABA29.2.4creepagedistanceforfunctioninsulationCreepagedistancesmaybereducediftheappliancecomplieswithclause19withthefunctionalinsulationshort-circuited.Forexample:ElectroniccomponentElectroniccomponentThetransistorleadslimitationofcreepagedistanceLivePartSupplementaryinsulation(1mm)Basicinsulation29.3.1Materialthicknessrequirementforsupplementaryinsulation(1)SupplementaryInsulationLivePartReinforcedinsulation(2mm)29.3.1Materialthicknessrequirementforreinforcedinsulation(1)ReinforcedInsulationLivePart1stlayerinsulation2ndlayerinsulationEachofthelayersshouldwithstandstheelectricstrengthtestforsupplementaryinsulation29.3.2Materialrequirementforsupplementaryinsulation(2)Basicinsulation29.3.2Materialrequirementforreinforcedinsulation(2)LivePart1stlayerinsulation2ndlayerinsulation3rdlayerinsulationAnytwolayerstogethershouldwithstandstheelectricstrengthtestforreinforcedinsulation= 1mmCase2ClearanceCreepage distance1mmCase3ClearanceCreepage distancePath under consideration includes a V shaped groove with internal angle of less than 80and with a width greater than 1mmCase4ClearanceCreepage distanceCase5ClearanceCreepage distance1mm