ISO 21857-2021标准规范下载简介
ISO 21857-2021管道系统杂散电流腐蚀的影响防护45-68.pdfF1 General
IS021857:2021(E)
Annex F (informative)
AlternatingCurrentInterference
广州流花商场中央空调系统施工组织方案Alternating Current Interferel
F2 LFI Calculations
IS0 21857:2021(E)
asashieldingwire(s).DuetothecloseproximityoftheEWwiththeenergizedphaseconductors,some current is induced ontheEW.This current isflowingalongtheearth wireand isproducingan induced emf on thepipeline in additiontotheemf produced by thephase conductors. Thetotal inductive couplingon thepipeline is,therefore, determined bythecurrents flowingthrough heenergizedphaseconductorsaswell asthroughtheearthwire.Thelocationoftheearthwirewith respecttothephaseconductors canbecriticalwhencalculatingLFIonnearbypipelines. Thelocationoftheearthwireonalatticetower,with respecttothephaseconductors,isdeterminedby the shielding angle.This angle should be sufficient to protect phase conductors from lightning strike. FigureF.1 illustratesthedifference inthecalculated inducedvoltageonthepipefortheearthwireat differentpositionsbetween0mand16m.FromOmto8mthereisadecreasingadverseeffectand from8mto16mthereisan increasingbeneficialeffect.
alculation examples(withoutandwi
Case 1.Noearth wire VectorphasecurrentA(A)
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lerahighvoltagepowerlinewithoneoverhead
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Tidal Effects
Photovoltaicinterferenceonburiedp
DC PhotovoltaicInterferenceresultsfrom conductive coupling
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Annex H (informative)
Photovoltaic interference
npart of thenormal DCleakageemanatingfromthePhotovoltaic (PV)Systemreturnsto t em'searth viaan interfered system (i.e.buried pipeline)and
JG_T158-2013胶粉聚苯颗粒外墙外保温系统材料H.2SourceofDcleakagecurrents
photovoltaicModules DC cables; inverters
Fora certainvoltagelevel,theDcleakageisdependentontheeffective insulationresistance(Riso)of chesystem.TheeffectiveinsulationresistancecanbemeasuredbeforeconnectingthePvsystemtothe grid[i4l andwill providean indicationof themagnitudeoftheanticipatedleakagecurrentstoground. Thelevel (magnitude)ofDcleakagecurrent isdependentonexternal factorssuchassolarirradiance ambienttemperature,degradedsealantsandmoistureingressatthemodules'level,soilresistivity,etc.
H.2.2Undetected faultconditions
DCleakagecurrentstoground maybe sourced
Faults on the DC sidecan befound inboth grounded and floatingPV systems.The detection mechanisms of these faults depend upon the DC grounding characteristics of the PV system and are inevitably different for grounded and floating configurations[i5]. These faults can remain undetected since the allowable DCfault detection thresholds can be set high,to avoid lost production from false detections or"nuisance"trips from regular and inevitableleakage currents. The undetected DC faults arise as the
TCECS283-2017 固模剪力墙结构技术规程.pdfIS0 21857:2021(E)
existingdetectionthresholdsforpermissibleDCleakagefromPsystemshavebeenbasedonother issues suchas fireprevention orpersonnel safety.