Application of IEL 62305-2 risk analysis standard in France · PDF fileApplication of IEL 62305-2 risk analysis standard in France. 9. International Symposium on lightning protection,

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Application of IEL 62305-2 risk analysis standard inFrance

Alain Rousseau, Pierre Gruet

To cite this version:Alain Rousseau, Pierre Gruet. Application of IEL 62305-2 risk analysis standard in France. 9.International Symposium on lightning protection, Nov 2007, Foz do Iguaçu, Brazil. pp.433-438, 2007.<ineris-00973277v2>

APPLICATION OF IEC 62305-2 RISK ANALYSI S STANDARD IN FRANCE

Alain Rousseau Pierre GruetSEFTIM INERIS

[email protected] [email protected] 49 Rue la Bienfaisance 94300 Vincennes

Abstract - France standard board (UTE) has publishedIEC/EN 62305-2 in January 2005, more than one yearbefore publication of the standard at IEC or EN level.Purpose was to gain experience when the voting stageoccurred for this standard in 2006. UTE has alsodevelopped a specific software to apply this riskassessment methode. By now we have more than 2years of application of both standard and software.The software called Jupiter is just a tool but it helps alot in introducing data and making easy calculations.This software introduces features such as drawing ofthe building to calculate accurate collection areas,design of the lines and of circuitr y inside the building,evaluation of fir e risk existing inside the structure,accurate selection of the needed SPDs as well as anautomatic provider of protection solution. This meansthat studies for simple building may be done bycontractors when more complete studies still need tobe done by experts but their task becomes a lot easier.This is perfectly in line with the Qualifoudrequalification scheme introduced by INERI S in France.We have now applied this risk method on a largeamount of structures with various risks (explosive,radioactive, fir e ...). Purpose of this paper is to sharethis experience and to discuss applicabilit y of someparameters introduced in the standard IEC/EN62305-2.

1 INTRODUCTIO N

IEC 62305-2 standard for risk assessment has beenpublished in Europe as EN 62305-2, at the latest byOctober 2006 depending on the countries. When thestandard can be implemented or not at IEC level it has tobe implemented by law in Europe. France has decided toremove immediately all his previous risk evaluationmethods as early as April 2006. This standard is part ofthe group of new standards that IEC TC81 (InternationalElectrical Commission - technical committee N°81 incharge of lightning protection of structures) has released.62305-1 deals with general information regardinglightning

62305-2 deals with risk assessment : do I need protectionand if answer is yes which one ?

62305-3 deals with lightning protection systems (LPS) :how to set-up such a system and select its components ?62305-4 deals with lightning electromagnetic pulse(LEMP) : how to set-up and design shields and bondingas well as selection of SPDs (surge protective device)used for equipotentiality ?France was using so far its own standards for risk (eitherrisk against direct lightning NFC 17-100 or risk againstinduced surges C 15-443. From time to time we were alsousing IEC 61662 (ancestor of IEC 62305-2) for complexsites such as military or nuclear plants. Recognizing thatmethod described in 62305-2 is more powerful andconsistent than previous methods, French NationalCommittee has decided to publish EN 62305-2 in a draftmature version in January 2005 under number 17-100-2.Purpose of this was to get experience on this method andbeen able to make comments and propose improvementsespecially at CENELEC level. Since publication of thisdocument the method has been extensively applied by theauthors on many site including chemical sites, explosivesites as well as other industrial sites.

2 IEC/EN 62305-2 METHO D

The new method is not so different in essence from theoriginal one (IEC 61662) but many parameters have beenrefined. Opposed to other French methods, this one ispurely based on probabilistic calculations and theparameters are coming from international scientificstudies which have been largely documented andpublished (SIPDA, ICLP ...). This is very important asusers of the method are sometimes suspicious of thevalidty of some parameters.

4 sources of damage are defined : flashes to a structure,flashes near a structure, flashes to a service and flashesnear a service.3 types of damages are defined : injuries to living beings;physical damage (damage to the structure i.e. destructionby direct hit, fire, explosion ...) and failures of electricalequipments.4 types of losses are defined : loss of human life, loss ofservice to the public, loss of cultural heritage and loss of

economic value (structure and its content, service and lossof activity). For each of this loss a risk is defined.

The total risk is then calculated has a sum of riskcomponents defined below :

Risk component for a structure due to flashes direct to thestructure :

• RA: component related to injuries of livingbeings caused by touch and step voltages in the zones upto 3 m outside the structure;

• RB: component related to physical damagecaused by dangerous sparking inside the structuretriggering fire or explosion, which may also endanger theenvironment;

• RC: component related to failure of internalsystems caused by LEMP;

Risk component for a structure due to flashes near thestructure :

• RM: component related to failure of internalsystems caused by LEMP;

Risk components for a structure due to flashes to aservice connected to the structure :

• RU: component related to injuries of livingbeings caused by touch voltage inside the structure, dueto lightning current injected in a line entering thestructure.

• RV: component related to physical damage (fireor explosion triggered by dangerous sparking betweenexternal installation and metallic parts generally at theentrance point of the line into the structure) due tolightning current transmitted through or along incomingservices;

• RW: component related to failure of internalsystems caused by overvoltages induced on incominglines and transmitted to the structure.;

Risk component for a structure due to flashes near aservice connected to the structure

• RZ: component related to failure of internalsystems caused by overvoltages induced on incominglines and transmitted to the structure;

For each of the risk associated to the 4 types of losses(called R1 to R4) and which need to be considered for thestudied structure, the total risk wil l be calculated as a sumof the above described risk components.Each of the risk components itself wil l be calculated byusing the generic formula given belowRX = NXPXLXNX is the number of dangerous events for that riskPX is the probability of damage for that risk;L X is the consequent loss for that riskAnd X can take the values A, B, C, M, U, V, W or Z

The risk component is defined as the number of lightningstrikes on the building multiplied by the probability thatthis strike lead to a damage (hopefully not all strikes wil lcreate a damage) and multiplied by a loss factor takingcare of the amount of losses (how many people arepossibly injured, what are the possible protectionmeasures)For risk R1 to R3 the total risk need to be lower than theacceptable risk RT given in the standard.

Table 1 : Typical values of tolerable risk RT

Types of lossLoss of human lif e (R1)

Loss of service to the public(R2) and Loss of cultural

heritage (R3)

RT (year-1)1(T5

1(T3

For risk R4 there is no tolerable risk as the economicperception is different from a small company to a largegroup. Calculation is then made by comparing annualamount of losses without protection, annual amount ofresidual losses as soon as protection measures areimplemented and annual cost of protection measurestaking care of maintenance. The result is then an annualsaving for the owner of the structure.

Let's imagine a telecom center (service to the public)which is located inside a building which is a nationalheritage. The owner of the building is willin g to know iflightning protection wil l provide some savings to him. Inaddition, risk for loss of human lif e needs to beconsidered as there are some people inside (workers andcustomers). In such case risk R1, R2, R3 and R4 wil l becalculated. For each of the risk the appropriate protectionmeasures may differ. For the simplest case of a buildingwhere only protection of human being is considered thenonly R1 wil l be calculated. R1 is also the risk which iscalculated for sites where environemtal risk need to beaddressed.

When risk cannot be sufficiently reduced, it is possible todefined specific zones inside the building to better protectthe areas which are the more dangerous and avoidoverprotecting the complete building.

3 TOOLS DEVELOPED TO APPLY THI SMETHO D

As previously mentioned, this IEC standard became aFrench document in January 2005. As such it is used andwil l be used more and more and wil l replace existingdocuments dealing with the same topic. To allow the useof this standard for most of the lightning professionals ithas been decided to provide tools to the user in order tofacilitate his job. These tools are described below.

3.1 Forms

INERIS has developed in France a qualification forlightning protection professionals. This is calledQualifoudre. Under this qualification scheme, aprofessional can claim expertise for site survey,production of lightning protection equipment, set-up ofprotection measures and control of installations. Hisexpertise in the selected field is attested by a letter whichcan be S for professional being able to work on simplestructures (a house, small office) or C for complexstructures (chemical plant for example) or even I forintermediate ones (not a simple nor a complex structure).The qualification is approved by the Lightning ProtectionAssociation (APF), the Ministry of ecology, the Ministeryof defense and the Federation of the insurance companies.For companies which are claiming study capability "C"their ability to use UTE C 17-100-2 risk method needs tobe proved. Under the Qualifoudre scheme many helpingtools are provided to qualified companies, one of thembeing a form to facilitate on site data collection. As amatter of fact, the new method needs a better cooperationbetween the plant manager and the lightning engineer.This form (which is sent prior to the survey to the plantmanager) is then useful to be sure that there is nomisunderstanding on the amount of time the planttechnicians need to involve for that action from one sideand to be sure that, on the other side, at data collectiontime, no parameters is forgotten by the lightning engineer

Table 2: Data collection form

Data collection form of a structureto be protected against lightning

STRUCTURE (N°, name, function)Dimensions (Length, width, maximumheight, height of chimney)Relative situation of the structureNumber of floorType of wall (concrete, metal, wood...)Type of roof (concrete, metal, asbestoscement, tile...)Type of soil inside structure (concrete,linoleum, wood...)Distance between the metal frameResistivity of the ground (ohm.m)Type of soil (clay, granite, silica, humus...)Are metal part equipotentially bonded ?Are reinforcements of the concreteconnected into a mesh ? (mesh size ?)Numbers of electrodes for lightning earth.Surge counters (indication on the counter)Installation of SPDs on the powerlines (typeof protection, state).Fire protection (simple detection, automaticextinction, extinguisher, presence offireman or time before their intervention)

B120x20x10mIsolated1ConcreteTiles

Concrete

2m300 Q..mClayYes0,2

21(0)Type 1SPDsManual fireextingui-shers

Fig. 1. First page (example) of Qualifoudre datacollection form

In addition, under the Qualifoudre banner, an internetforum offers possibility to the users of the method toexchange on problems encountered or even to ask forsome help.

3.2 Jupiter software

The software is taking into account all the parametersdescribed in the standard and offer to the user practicalfacilities such as the possibility to test immediatelyvarious possible protection means effect and selection ofthe most convenient one.Based on the data collected on site, the parametersdescribing the structure can be filled. There areinteresting features in the software such as truecalculation of the collection area taking care of realdimensions or evaluation based on fire brigade rules ofthe fire risk.

Collectio n Area Ad [kirfj :

| 5.51 E-02

Collectio n area Am [km 1].

| 3.HE-01

Show Am

Fig. 1. Exemple of calculation of the collection area

When the data regarding the structure and its connectedservices are introduced the risk calculation can start. Thislead to a diagram as in Figure 2.

=-03'

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E-03'

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E-03

E-03

E-03

E-03

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E-04

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Total risk value BI^B(sum of riskcomponents RAtoRz)

: : : :Tolerablerisk(10 -5forthat rcase, r ISK R 1 )t 2SE-51

27É-4I

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J c o ' a l - J M - OOEOL.,. ooEQl.. 27E-10L.

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Fig. 2. Typical screen where the protection measures havenot been implemented

As it can been seen there is a graphic display of theconclusions of the analysis : the building is not selfprotected. The user of the software should thenintroduced protection measures in order to bring the totalrisk below the red bottom line (tolerable risk)

Fig. 3. Typical screen where the protection measures havebeen implemented

With this software you also have access to many features.One of them is the green/red color code. Every riskcomponent which is red is greater than tolerable risk. It isgreen in the other case. It is then very easy to determinethe part or the zone of structure which needs a specialcare. This is reported on a specific screen where influenceof each zone can be appreciated.

. - . x

• r •• <

• r •• <

ZÎ

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.ff J. . . .—

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Fig. 4. Influence of various zones on the total risk

The software propose some protection solution in anautomatic way that the user can use or not. The economicevaluation and selection of appropriate SPD is also veryeasy due to a large data base of parameters and cost thatthe user can manage by himself based on his ownexperience.

3 APPLICATIO N OF JUPITER ON EXPLOSIVESITES

.Sometimes the danger is very high and the potentialdamages are important. It is the case for installations withrisk of explosion and with people in the lethal zone. If theduration of the risk of explosion is not well indicated, thecalculated risk can be overestimated. In this case, ithappens that the addition of protections with the bestpossible effectiveness does not reduce the risk under thetolerable value of 10-5. This too huge risk wil l in factmask the other risk which even if less important are notminors. A good example is the risk of fire which is oftenpresent when there is explosive risk. It is then necessaryto consider 2 situations: a normal situation during whichthe risk is for example the risk fire and a degradedsituation where explosion can occur.Let us suppose that the building to be protected is awarehouse storing solvent. Storage is very flammable andthe interior of the building is classified ATEX (level 2)which means explosive atmosphere for short durationsnot exceeding a cumulative annual time of 100 hours. Asthe fire risk is present for 1 800 hours we need to considerthis duration. But, by considering that storage is explosiveand that the people are present in the zone during 1800hours (even if the potential explosive risk is present foronly 100 hours), the risk cannot be reduced with bestavailable protections means.

3E4ZSE-H4E42

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Fig. 5. Protection measures have not been implemented

Calculation must then be carried out for 2 situations. Innormal situation only the fire risk is considered andduration is 1 800 hours. It is possible to use protectionmeans to reduce the risk to a tolerable value. In degradedsituation, the explosion risk is considered but the durationof presence of the people in the zone at the risk is only100 hours.

Figure 8 shows that the risk calculated for duration of 100hours with explosive atmosphere is lower than thetolerable value. The probability that the lightning strikesthe warehouse and be the trigger of an explosion is lowdue to the short duration of 100 hours.

44 10-647 10,-6 , , , ,

: Best protectionsare insufficient

V. qQ RC tU HU * V *<1 1£ 'CJ

Fig. 6. Best protection measures have been implemented

Al l JTP H J U •n q »

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Fig. 7. Protection measures have been implemented

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Fig. 8. Whithout protection measures but duration 100 h

When calculation is carried out for various situations, it isthen necessary to install the protection means whichreduce the risk in all the cases. In the above example, theprotection means which reduces the risk as in figure 7meets the need.

4 NEED FOR CLARIFICATIO N

No doubt that IEC/EN 62305-2) is a powerful tool.However, it is needed to clarify a few things to cover allthe needs of the French lightning protection community(and perhaps of other countries too).More than 150 buildings have been studied in Franceusing UTE C 17-100-2 method over a period of 2 year.Plants had different characteristics and covered a widerange of industrial site and buildings. Based onapplication of the method on a large number of cases itappeared that a few parameters needed to be betterdefined.

4.1 SPDs

There is no relationship between SPD characteristics andprobability values that you can select in the standard. Ofcourse, when you are an expert you know how to selectthe appropriate SPD and if one SPD is better thananother. But who is really able to select the probabilityassociated with an SPD which is behaving better than therequirements given by the calculation. An SPD protectingat 1 kV for a fixed value of current offers a betterprotection than an SPD protecting at 1,5 kV for the samevalue of current. How can we quantify this? If the neededprotection level is 1,5 kV and the needed lightningdischarge capacity is 10 kA 10/350 who could say whichof the following SPDs is the best? SPD1 has a currentcapability of 40 kA 10/350 and protective level of 1,5 kV.SPD2 has a current capability of 15 kA 10/350 only but aprotective level of 1 kV. It is already not easy to say whatis the best choice but it is furthermore difficult toassociate probabilities to both. Mainly the document isrelated to probabilities associated to currents withstandwhich is probably one of the good parameter to avoidflashover problems at the entrance of installation (but notthe only one) but which is quite irrelevant whendownstream protection is needed (coordinated SPDs). Inaddition, to mix SPD with lightning protection level ofthe LPS creates confusion. What to do when there is noLPS and direct lightning is not relevant? SPD areclarified in Europe by type related to testing capabilities.To have a SPD Type 1 (the one used in case of LPS)defined for a lightning protection level 3 for example canonly create confusion. Better coordination is neededbetween LPS and SPD standards and SPD probabilitiesshould be better defined in the risk standard. Jupiterprovides some tools to help selecting appropriate SPDsbut the standard should be more detailed regarding thisissue and avoid confusion in the head of the reader.

4.2 Concept of coordinated SPDs

You need to use SPDs in front of each sensitiveequipment and SPDs should all be coordinated together.But if you use only entrance SPDs (SPDs for

equipotentiality) and other SPDs in front of a particularzone (with a high fire risk for example) are youcomplying with criteria to consider you have acoordinated system? It seems that it is not the case basedon present definition when in practice such a protection atneeded place will be sufficient.

4.3 Shielding of cables

The key parameter is the shield resistance. Who is able togive this value in practice? Surely not the electricaltechnician responsible for the building. Should we makemeasurements? Try to locate the manufacturer referencenumber and try to get data from him? If you have manydays in front of view it is perhaps possible but for most ofthe cases a simplification is needed. This non practicalitywil l lead countries to develop alternative method for theircontractors and this approach is going against the initialtarget.

4.4 Number of people injured inside a buildin g in caseof a lightnin g strike

In some cases this data can be obtained from discussionsbetween the structure owner or manager and the lightningexpert but in a lot of other cases this is quite difficult toachieve. If you use the generic values proposed by thestandard you will get a protection scheme which is clearlyover designed. In some cases you will not be able toreduce the risk below the tolerable risk and this meansaccording to the French law that you may not be able torun your plant! The only remaining solution is then toinstall storm detectors and stop this critical activity duringstormy periods.

4.5 External zones

They are only considered for the risk of touch and stepvoltage. But if you have an explosive area in the buildingor if you store dangerous products with possible impacton environment it is likely that people outside thebuilding wil l be injured and not due to step and touchvoltage. This needs to be considered. In addition, when atoxic cloud is released to the atmosphere in case of surgesgenerated by a lightning strike, how should we considerthe number of people potentially injured? 1 000, possiblymore ... This should be better defined in the standard. Inthe same way, if a truck is bringing explosive materialfrom the outside, its presence outside of the buildingshould be also taking into account in the explosive risk.Protection of external zone should take into account otheraspects than the pure risk of touch and step voltage.

4.4 Storm detectors

So far, the only solution in some cases to reduce the riskbelow tolerable risk is to use a storm detector. Simpleway of doing so is to consider that there is nobody in thedangerous zone in such a case (once again this does notcover the risk of people being outside the building or of areleased chemical cloud spreading around). But in fact, astorm detector has also an efficiency. It may not detect100% of all storms. In some cases, the user wil l changethe settings in order to avoid too many false alarmsleading to a detection ratio of less than 100%. In such acase, such a ratio cannot be introduced in the method. Ofcourse, there is no standard for such storm detectors sofar in spite of some attempt in France and at Ceneleclevel, but we cannot ignored such a tool for the riskevaluation and a probability should be associated to it inthe same way it is for SPDs or LPS.

4 CONCLUSIONS

French national committee has decided in January 2005 toimplement the draft international standard IEC 62305-2into a French document. This is clearly supported by mostof the actors and especially INERIS which has includedthis requirement in his qualification scheme namedQualifoudre. To support this development, tools havebeen developed and UTE, the French electrical standardbody, has developed a powerful software named Jupiter.This will allow a greater number of people to use themethod. At the same time, to allow this general use, a fewparameters need to be clarified. They are accessible to thelightning expert, even if in some cases it may be quitedifficul t to get the data or relate these data to probabilityvalues. But for less skilled users, the task may bediscouraging. The risk calculation being so powerful itshould be a pity to not make the necessary clarificationswhich wil l make this document the only reference inlightning risk management.

5 REFERENCES

[1] UTE C 17-100-2, Guide pratique protection contre la foudrepartie 2 évaluation des risques, January 2005.

[2] CEI 62305-2, Protection against lightning part 2 riskmanagement, January 2006.

[3] "Qualifoudre", Rule and Qualifoudre reference frame for thequalification of the lightning professionals, February 2005.