m. cotterell _photovoltaics and fire: international activities--an iec convenors perspective

Martin Cotterell

Photovoltaics and fire

International activities – an IEC convenor’s perspective

Sundogs (or parhelia) are brilliant spots of light sometimes seen around a solar halo

PV and fire has been a hot topic for last few years within PV community

Not possible to cover all activities in a short presentation … the following is a selection of some of the activities

Sundog Energy

Installing systems since 1995

Experience from hundreds of projects across the UK – all types & scale of systems

Martin Cotterell

Co-convenor IEC TC82 WG3

MCS … PV & roofing groups(Guide to the Installation of PV systems)

Three main areas for consideration ...

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Design / safety in event of a fire

PV arcs(prevention & detection)

Effect on building flammability

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Integrated systems

Building codesEurope >> DRAFT prEN50XXX BIPV

61730 PV module safety qualificationNWIP PV systems on buildings ?

UK …Building regulationsMCS 017

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• Spread of flame (UL790) – adverse effectfound … Magnitude / extent depends oninstallation parameters (eg gap behind array,set-back from eaves)

• Burning brand – may cause adverse effect

Recommendations• More research needed• Test whole systems• More study on installation measures that

may mitigate effects

NWIP PV systems on buildings ??

UL study on effect of “on-top” systems

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Risk of DC shock to fire-fighters ?

Need to understand risk Includes considerations of working

practices

UL looking at quantifying risk, mitigation and working practices (in US)

Some similar work around world including Europe (more later today)

Direct contact

Shock hazard through water jet?

UL work includes …

Shock hazard through water jet’s andpresence of water during fire-fighting

Shock hazard via smashed modulesand exposed parts during fire-fighting

Emergency disconnect & disruptiontechniques

Cutting live DC conductors

PV generation under low and artificiallight and light from a fire

Potential hazard from PV modules &components damaged by fire

More on these topics later today

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Risk of DC shock to fire-fighters ?Design measures to mitigate risk …

• Routing and containment of DC cables• Location of components• Voltage limits• DC isolation (manual / auto)• AC module systems• Module electronics• Signage

• IEC 62548 Design requirements forPV arrays

• IEC NWIP PV systems on buildings ?• IEC 60364-7-712 (BS7671)

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DC isolation

Lots of options suggested Issue led by manufacturers in some quarters?

DC isolator strategies …• Manual• Remote (motor driven)• Thermal • Module level switching

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DC isolation

Considerations:• When and where required• Real benefit?• Reliability (failsafe?)• Array / string / module • Open circuit or short circuit?• Yield losses & costs

Requires clear guidance in installation standards



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Preventing PV systems being a source of fire

Safe design + high quality installation

Using high quality parts

Inspection and testing





IEC product standards …• Modules• Inverters & conversion devices• BOS (cables, switches, JBs etc)• Materials





IEC 62446 Grid connected photovoltaic systems Minimum requirements for system documentation, commissioning tests and inspection

IEC 60364-7-712 (BS7671)





Past 3 slides … IEC activities that are fairly well known about and understoodTo get maximum effectiveness need:• Training• Compliance checking / certification schemes … eg MCS

But what can be done if an arc occurs …

PV arc fault detection

Need to understand scenarios …

Series arcs Parallel arcs

Arc Fault Circuit Interrupter (AFCI)

“A device intended to provide protection from the effects of arc faults by recognizingcharacteristics unique to arcing and by functioning to de-energize the circuit when an arcfault is detected.”

National Electrical Code (US, 2011)

… all PV systems with DC circuits operating at 80 volts orgreater on a building to be protected by an AFCI, PV type,or other system components listed to provide equivalentprotection …

• Can be standalone device or built into otherequipment (eg inverter)

• Requires a visual indicator and manual re-start

• Only comes into force once devices are commerciallyavailable

• Only addresses series arcs

Arc Fault Circuit Interrupter (AFCI)

UL1699B now published, implementation willbegin as soon as manufacturers can get theirdevices Listed. No Listed devices or ListedAFCI-equipped inverters were available as ofMay 2011

NWIP submitted to IEC AC AFCI

AFCI challenges

• Detection of arcs may be made difficult by external noise sources & attenuation

• Series arc interruption is easy - open the circuit at any point

• Parallel arc interruption not so simple (short circuit or open circuit the source)

• Wrong action can make the arc worse

AFCI only part of the solution

Other measures include …

• Some parallel arc scenarios can bedetected & prevented through isolationmonitoring (ungrounded systems only)

• System design strategies to reducevoltage (AC modules, DC:DC convertors)

… and prevention is the best answer!

Poor cabling – an arc waiting to happen?

Summary

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Bit of a whistle-stop tour, but …

• International activities across all three issues • Some work-streams significantly more established than others• IEC developing standards - but some key ones are only NWIPs

thank [email protected]

m. cotterell _photovoltaics and fire: international activities--an iec convenors perspective

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