1) Mineral insulated cables are an alternative to standard fire-resistant cables as they are completely uncombustible, extremely robust, and can survive fires rather than just maintain functionality for a limited time. 2) Current fire safety standards have gaps as they do not accurately simulate real fire conditions or account for how the rising temperature affects copper's resistivity under fire. 3) As copper's resistivity increases five times under fire temperatures, the cable temperature rise at full load would be dangerously high, potentially melting the copper, regardless of the length exposed to the fire. All fire standards would need to be upgraded to account for this.

1. Whichcableisreallyfireresistant? Stefan Fassbinder Deutsches Kupferinstitut Am Bonneshof 5 D-40474 Düsseldorf Tel.: +49 211 4796-323 Fax: +49 211 4796-310 sfassbinder@kupferinstitut.de stf@eurocopper.org www.kupferinstitut.de www.leonardo-energy.org

3. The skilled trades

4. Industry

5. R & D institutes

6. Universities

7. Artists and craftsmen

8. Students

10. phone

11. fax

12. e-mail

13. internet

14. online database, or

16. Limited fuelenergy per unitbuildingspace,

17. Low fumes / lowtoxicity (nohalogens),

18. andpriorto all sustainedfunctionalityfor a definedperiod of timeso thataccidentslikethefire at Düsseldorf Airport on 11 April 1996 that left 17 people dead shall have the minimum possible impact – if they cannot be totally avoided.

21. Mineral insulatedcablescouldbe an alternative! Theyconsistexclusively of metals and minerals Copper conductor, meltingpoint: 1083°C Magnesia oxide, meltingpoint: 2800°C Outer copper sheath, meltingpoint: 1083°C

23. they are extremelysturdy and robust,

24. theyevensurvive a fireratherthan just toremainfunctionalfor a limitedperiod of time,

25. theyeven come at a lower price

29. Special cableglands will beneeded, tobefixedwithsomespecializedtoolsandrequiringsomespecialskills

30. Verypliable but replacingelasticwithplasticdeformation. Just don‘tbendtoooften:Work hardening!

31. Beyondthis, just onemoredisadvantagetocopewith: Marking of conductorsismissing

32. Further opportunityforapplication: Hisorically relevant sites Whereisthecable? Thereitis!

33. Whereisthecable? Thereitis!

34. But nowitbecomesreallydifficult: Thereitis!

36. Underfireconditionsthecableover-temperatureaboveambientincreases.The formerissueistakenintoaccount in thestandards. The latteris not!

37. Sideissue 2: Calculation of the copper temperaturerise Excludingthebcoefficient: Includingthebcoefficient: Accordingto EN 60742: Wiedemann-Franz Law: x = 234.5,α = 3.9*10-3andβ = 0.6*10-6forcopper

38. The differenceisinsignificant in therange of normal operatingtemperatures

39. The differenceisverysignificant in therange of ambienttemperatures of a fire!

41. to 950°C in thecase of a fire,

42. theresistivity of copper risesby a factor of 5!Standards taketheresultingincrease of thevoltagedropintoconsideration – but onlyfor a fraction of thecablelength. Thisisjustifiedbecauseonly a fraction of theentirecablerun will beexposedto a fire…

45. Meltingpoint of copper: 1083°C.

46. (Of aluminium not eventospeak: 650°C).All relevant standardsdealingwiththisrequire an upgrade! In theory all »fireproof« or »fireretardant« safetycableswouldneedtobedesignedwith 5 timesthecrosssection a standardcablehasforthe same currentrating. In practice a compromiseneedstobefound. After all, mineralinsulatedcableswouldbethebetterchoice in anycase!