ISO 21857-2021标准规范下载简介：
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ISO 21857-2021管道系统杂散电流腐蚀的影响防护45-68.pdfphotovoltaicModules 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
JJF 1267-2010 同位素稀释质谱基准方法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
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existingdetectionthresholdsforpermissibleDCleakagefromPsystemshavebeenbasedonother issues suchas fireprevention orpersonnel safety.
If the PV system's fault detector/interrupterisblind tohigh impedance faults,theleakage current to ground may exist indefinitely (provided that it is not sufficiently high to cause arcing and fire). The atter implies that thePV array will continueto operate with a permanent reduction inpower output. Briefly,intheevent ofanundetectedground faulttheMPPT (maximumpowerpointtracker) of the nverter will seta new operating pointto a lower powerthanbefore thefault.This is because the MPPT may take thefault as an ordinarypower drop (usuallycaused by changing irradiance)and will shift the operationtoanewoptimalpowerpoint
At the source level:
etecting DC leakagefaults ingrounded PV systems, the UL 1741[16] and the NEC[iZ] require t) llation of a GroundFault Protection Device (GFPD).These devices are designed to interru) lowofDCfaultcurrentsandalsotoalertaboutfaultoccurrences.
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Cleakagetogrounc arising from these cables will be limited
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Modelling the effects of stray current interference on cathodically
L.1 Introduction
Before the modelling process begins it is important to clearly define the purpose of the modelling as wellasthedesiredoutputs.
sired outputs from the model will define what is required by the end user. Usually this is a portwithgraphs,imagesandtablesalongwith descriptivetext.Itcanalso includeelectronic atallowsimplemanipulationandviewingofthemodel.
Detailedinformationofthepipelineisrequired Suchdetailcanincludethefollowing:
Operatingcharacteristics
Outside diameter; 2) Length; 3) Route; 4) Geometry; Date of installation; 6) Design life;
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I.3Model specification
odel methodology
A valid methodology is to
break the pipeline down into segments that can be considered as having substantially identical electricalcharacteristics, b)calculatethe impedancefor the segments, taking into account the effect of the coating and soil conditions,and ， resolvethevalues ofthevoltagenodes.
I5Model validation
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Assessment ofthe corrosionriskfor steel in concrete orfor
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TableJ.1 (continued)
TableJ.1 (continued)
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Key X time, in s pipe to soil potential, in V
Fromthisdataitispossibletodetermine
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d)Calculate the sum of the E,values and divide by N. This produces AE.avg,which is proportional to Q..
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NY/T 2976-2016 绿色食品 冷藏、速冻调制水产品Annex K (informative)
Principles ofanodic and cathodic interference
FigureK.2showstheprincipleofinterferenceduetocathodicpotentialgradients.
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fureK.3shows theprincipleof interferenceduetoanodicpotentialgradients.
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JB/T 6428-2016 无润滑往复活塞高纯氮气压缩机Bibliography
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