photographie

E/CT 166, first issued 1993, january

n° 166enclosures anddegrees ofprotection

Jean Pasteau

Graduated in physics sciences in1959, he joined Merlin Gerin in1962 in the air-blast circuit-breaker design-office where hewas mainly in charge of thepreparation and follow-up of thetechnical part of contracts.Since 1983 he has beenTechnical Delegate for MerlinGerin in standardization bodies(IEC, UTE, CENELEC,...)That led to him becoming inparticular:■ chairman of the FrenchCommittee 70 in charge of thepreparation of standards for«Degrees of protection providedby enclosures» in 1987,■ convenor of the BTTF 68-3 incharge of the preparation of theEuropean standard for the IKCode in 1991.

Cahier Technique Merlin Gerin n° 166 / p.2

Cahier Technique Merlin Gerin n° 166 / p.3

enclosures and degrees of protection

summary

1. Introduction p. 42. General Definitions p. 5

Uses of a code system p. 63. The IP Code General p. 7

First numeral p. 7Second numeral p. 8Additional letter p. 9Supplementary letter p. 9

4. The IK Code Introduction p. 9Degrees of protection p. 10

5. Application to the design of electrical equipment p. 116. Conclusion p. 11Appendix 1: correspondence between the IP code andwater-tests of IEC 68-2-18 p. 12Appendix 2: equivalence between the old third numeralsof the french IP code and IK code p. 12Appendix 3: bibliography p. 12

The protection of persons against directcontacts is required by certainregulations (in France the Decret of the14th of November 1988), and specifiedby electrical installation standards, suchas IEC 364. On the other hand, types ofexternal stresses likely to influence thebehaviour of equipment are describedin IEC 721-2. The protection againstsome of these influences is oftenspecified in product standards.Therefore, to explain the degrees ofprotection that enclosures can provide,and how standards codify them,constitutes an essential information forall, prescribers, installers, operatorsand inspecting organizations, thepurpose of this «Cahier Technique». Itreplaces «Cahier Technique» No 6written in 1982, made obsolete by therevision of IEC 529.

Cahier Technique Merlin Gerin n° 166 / p.4

1. introduction

It is not sufficient that a piece ofequipment fulfils the functionalrequirements assigned to it. It also hasto be protected against possibleadverse external influences, andlikewise to ensure that it is not harmfulto the user or to the environment.

Different means can be used alone orcombined to comply with this lastrequirement. All of them derive fromone of the following methods:■ placing out of reach vertically orhorizontally, for instance by means ofan obstacle,■ total solid insulation as usedparticularly for cables, but which is noteasily applicable when moving partsare involved,■ putting into an enclosure, which is theobject of this «Cahier Technique».

This last method has the advantage ofproviding an easy solution to the otherrequirement, i.e. the protection ofequipment against certain influencessuch as:

■ the ingress of foreign bodies whichcould disturb the mechanical orelectrical operation. They comprise notonly sand and dust but also smallanimals and flying or creeping insects,■ water and other liquids which couldalter the insulation and generatedegradation,■ mechanical impacts which mightdeform or break brittle parts,■ corrosive gas from the environment,■ radiated electromagnetic fields,■ various radiations including light.

Constituting a supporting structure, theenclosure also allows for the building ofassemblies of complementary andcoordinated apparatus. Therefore it isthe most common method of protection.It is used for electronic or informationtechnology equipment as well as fordomestic appliances or for high or lowvoltage equipment, or for rotatingmachines. The enclosure may be builtinto the equipment or manufacturedseparately and sold empty to an

assembly-maker. It can be made ofvarious materials: metal or synthetic,insulating or conductive.

In order to facilitate the relationshipsbetween manufacturers, users andlegislators, standards defineterminology, characteristics and meansof checking a product, a service or aninstallation. As far as protectionprovided by enclosures is concerned, itis the aim of Publication 529 of the IECand of prEN 50102 of CENELEC (seecorresponding French standards inappendix 3). It must be noted at thispoint that standards define theprotections that enclosures canprovide, but not the characteristics ofthe enclosures themselves.These so-called «horizontal» standardsapply only when referred to by therelevant product standard. Byextension, degrees of protection byenclosures are also used tocharacterize protection provided bybarriers.

Cahier Technique Merlin Gerin n° 166 / p.5

2. general

definitionsTo understand the actual importance ofstandards, it is absolutely necessary torefer to the definitions of the vocabularyused, definitions which are themselvesstandardized for a given field. Someterms which are used when protectionof electrical equipment by enclosure isreferred to are therefore givenhereafter. Given the extent ofinternational trading connections, thecorresponding French terms are alsoprovided. The reference which issometimes stated just after, is the indexof the term in the InternationalElectrotechnical Vocabulary (IEV).

■ enclosure (enveloppe) IEV 826-03-12«A part providing protection ofequipment against certain externalinfluences and, in any direction,protection against direct contact».

IEC 529 adds the following note:This definition taken from the existingIEV needs the following explanationsunder the scope of this standard:«1) enclosures provide protection ofpersons or livestock against access tohazardous parts, 2) barriers, shapes of openings or anyother means - whether attached to theenclosure or formed by the enclosedequipment - suitable to prevent or limit thepenetration of the specified test probesare considered as a part of the enclosure,except when they can be removed withoutthe use of a key or tool».Figures 1 and 2 display this definition.

So enclosures provide protectionagainst direct contacts. The way theyare made can also participate into theprotection against indirect contactswhen the continuity of conducting partsis secured.

■ degree of protection (degré deprotection)«The extent of protection provided byan enclosure against access tohazardous parts, against ingress offoreign objects and/or against ingress ofwater and to give additional informationin connection with such protection».

tool, or the like, held by a person toverify adequate clearance fromhazardous parts».

The conventional approach of therepresentation of a part of the humanbody is to be noted here. The «jointed-test finger» does not pretend torepresent the longest nor the thinnestphalanges; it is only the name of a testprobe showing, typically, a finger.When a more selective protection islooked for, a higher degree should beused.

This type of probe is used to checkprotection of persons. The criterion topass a test with such a probe is that, ifit penetrates partially, the «adequatedistance» is kept.

■ hazardous part (partie dangereuse)«A part that is hazardous to approachor touch».It may refer to any kind of hazard:electrical (high or low voltage),mechanical, thermal or other.

■ adequate clearance for protectionagainst access to hazardous part(distance suffisante pour la protectioncontre l’accès aux parties dangereuses)«A distance to prevent contact orapproach of an access probe to ahazardous part».Distance is related to the internalvoltage of the equipment.

■ access probe (calibre d’accessibilité)«A test probe simulating in a conven-tional manner a part of a person or a

fig. 2: a fixed panel inside the enclosure prevents the «test probe» of 2.5 mm and of 1 mmdiameter (ø) from penetrating; therefore it is an IP2 XD (according to IEC 529).

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fig. 1: a mask in front of an opening prevents the «test probe» of 1 mm diameter (ø) frompenetrating and allows a degree of protection of IP3 XD (according to IEC 529).

Cahier Technique Merlin Gerin n° 166 / p.6

■ object-probe (calibre-objet)«A test probe simulating a solid foreignobject to verify the possibility of ingressinto an enclosure».

The test is satisfactory if the fulldiameter of the probe does not passthrough any opening, as the bore probe.

■ swichgear and controlgear(appareillage) IEV 441-11-01«A general term covering switchingdevices and their combination withassociated control, measuring, protec-tive and regulating equipment, alsoassemblies of such devices andequipment with associatedinterconnections, accessories,enclosures and supporting structures».

■ enclosed assembly (ensemble sousenveloppe) IEV 441-12-02

«An assembly enclosed on all sides,top and bottom in such a manner as toprovide a specified degree ofprotection».

uses of a code systemAccording to the dictionary, a code is«A set of rules on any subject, or a setof letters or figures or word groups witharbitrary meanings for brevity orsecrecy». Apart from the purpose ofsecrecy, both meanings apply to codesystems dealt with in this «CahierTechnique».A code system allows therepresentation by means of analphanumerical symbol, of propertiesaccording to their definitions and to theway they are tested.

It can be used in different directions:■ to specify required levels.It is the case of regulations relevant tothe protection of the public or ofworkers.It is also the case of some installationstandards for a particular environment;it can also be the case of a particularuser’s specification.■ for a manufacturer, to describe theproperties of his equipment.

Thus some product standards give aset of degrees of protection to choosein one direction or in an other.

As far as the protection provided byenclosures of electrical switchgear isconcerned, nowadays the internationalstandardization defines two codes: theIP code and the IK code.

Cahier Technique Merlin Gerin n° 166 / p.7

generalThe IP code is described inPublication 529 of the InternationalElectrotechnical Commission.IP means «International Protection».This code allows for the description ofthe degrees of protection provided byenclosures against access tohazardous parts, ingress of solidforeign bodies and against harmfuleffects of water, by means of thenumerals and letters describedhereunder.

This standardized code is intended tobe used in product standards. It canalso be used to describe an emptyenclosure, but then some difficultiescan appear as to the application:■ where to locate harmful parts tokeep them at «adequate distance»?■ where may water or dust depositwithout disturbing the correctoperation of the equipment?

In fact, degrees of protection will onlybe required when the enclosure is inservice with equipment inside.The assembler is thereforeresponsible for the final productcomplying to its standard. But themanufacturer of the enclosure muststate in the documents whereequipment has to be installed insidethe enclosure to maintain the degreesof protection he has assessed.Eventually, people in charge of theinstallation who will connect theequipment (cable pass), fix it and insome cases adapt auxiliaries (push-buttons, meters,...) must ensure thatthe specified degree of protection ismaintained.

Letters IP of the code are followed bytwo independent numerals andsometimes by letters. When thedegree of protection corresponding toone of the numerals is not stated (be itunnecessary or unknown) it isreplaced by an X.

first numeralAs a result of decisions made forprevious editions of the standard,decisions which cannot to bereconsidered, the first numeralindicates simultaneously :■ protection of persons against accessto harmful parts and■ protection of equipment againstingress of foreign bodies.To check compliance with the firstnumeral, two probes must therefore beused (an access-probe and an object-probe) with the application forcesspecified in the standard, or the sameprobe is used with two acceptancecriteria.

The various degrees correspond to thefollowing meanings:IP 1X: it can be a wire-mesh or anenclosure, the largest opening of whichdoes not allows a ball of 50 mmdiameter to ingress. This correspondsapproximately to the ingress of a hand(see fig. 3).

IP 2X: the protective wire-mesh hassmaller holes and the diameter of theobjet-probe is 12.5 mm. In addition, the«jointed test-finger» must stay atadequate distance from harmful parts.

IP 3X: the enclosure must not allowingress of foreign bodies 2.5 mm of

diameter. The test is performed with asteel wire with edges free from burrs,because the use of a 2.5 mm diameterball would not be convenient.

IP 4X: as for the previous degree butwith 1 mm instead of 2.5.

IP 5X and IP 6X: these two degreescorrespond to protection againstingress of dust. IP 5X allowspenetration of some dust in placeswhere it is not harmful. IP 6X acceptsno ingress of dust at all.The test is performed in a test roomwhere talcum powder is sustainedfloating by means of an air flow.In addition, the enclosure isdepressurised internally except if therelevant equipment standard specifiesthat it be of category 2: that is, thenormal operation of the enclosedassembly cannot generate significantinternal pressure reduction. Althoughthe test is performed with talcumpowder, the effects that might give anyother type of dust must be taken intoaccount here.

Dust-test of the IP code is currently tobe incorporated into IEC 68-2 as testLa2.

The indication provided by the firstnumeral implies that the equipmentcomplies with all lower degrees.

fig. 3: the ball does not enter, but the finger-tip touches the live part; therefore it is only IP 1X(according to IEC 529).

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3. the IP code

Cahier Technique Merlin Gerin n° 166 / p.8

second numeralThe second characteristic numeral ofthe IP code indicates the degree ofprotection against harmful effects ofwater penetration. It is specified thatthe tests be performed with freshwater (see fig. 4) with no wettingagents.

The interpretation of tests for thisnumeral may be difficult since waterpenetration into the enclosure ispermitted, provided it does notgenerate harmful effects.

The various degrees of the secondnumeral correspond to the followingsituations:

IP X1: this first degree correspond tothe protection against vertical waterdrops to which indoor equipment canbe exposed due to leaks orcondensation-drops from the ceiling ofthe room or on tubes passing abovethe enclosure.

IP X2: this degree corresponds also towater drops, but with a larger flow andwith an angle up to 15°. It is forinstance the case of equipment onships.

IP X3: this degree corresponds to theprotection against rain. The maximumspray angle is 60° from vertical. Thebase of the enclosure may be open.The test may be performed by meansof a oscillating arc-tube equipped withnozzles (over 60° from each side ofvertical) or of a mobile spray with amask limiting the incidence of the jets.In both cases, the water flow isspecified.

IP X4: the water flow of each nozzle isthe same for this degree as for theprevious one but there are nozzlesover 180°; in addition, the tubeoscillates over ± 180° so that water issprayed in every direction.This testsimulates heavy rain and splashes.

IP X5 and IP X6: these degrees aretested by water jet hose simulatingwater-jets, heavy sea, etc. Testconditions are more severe for degree6 than for degree 5: a larger diameterof the nozzle and water flow.

IP X7 and IP X8: no longercorrespond to water projections but totransient or permanent immersions.

fig. 4: test means provided by the standard to assess the second numeral of the IP code.

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IP X1 : protégé contre les chutesverticales de gouttes d'eau.

IP X2 : protégé contre les chutesde gouttes d'eau jusqu'à 15°de la verticale.

IP X3 : protégé contre l'eau en pluie. IP X4 : protégé contre les projections d'eau.

IP X5 : protégé contre les jets d'eau. IP X6 : protégé contre les paquets de meret projections assimilable.

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IP X7 : protégé contre les effetsd'une immersion temporaire.

IP X8 : matériel submersible(essais sur accord particulier).

Cahier Technique Merlin Gerin n° 166 / p.9

Therefore enclosures complying withthese degrees must have doublemarking if they also comply with a lowerdegree, for instance IP X5/X7 (a bucketimmersed upside down is IP X8, but notIP X4).

Water-tests of the IP code have beenrecently incorporated into IEC 68-2-18with the following correspondence (seeappendix 1).

additional letterIn some cases, the protection providedby an enclosure against access toharmful parts is better than indicated bythe first numeral (which also indicatesthe protection against ingress of foreignbodies). For instance it is frequently thecase of an opening of the enclosureblinded by a staggered joint or a sheet-bent. This protection can becharacterized by an additional letteradded after the two numerals. It allowsopenings useful for thermal dissipationwhen keeping the degree of protectionrequired for the protection of persons.

It has one of the following meanings:

IP XXA has no practical application sincethe test for the letter A is the same as forthe first numeral 1 (see fig. 3).

IP XXB means that foreign bodies ofdiameter larger than 12.5 mm can ingressinto the enclosure, but that the test-fingerdoes not penetrate more than 80 mm, i.e.not beyond its 50 x 20 mm

guard and stays at an adequate distancefrom harmful parts (see fig. 5).

IP XXC allows penetration of foreignbodies of diameter larger than 2.5 mm,but a straight steel wire of this diameterand 100 mm long stays at an adequatedistance from harmful parts.

IP XXD the situation is similar to theprevious degree, but for a diameter of1 mm.The additional letter is also used whenonly the protection of persons isaimed at.

supplementary letterThe IP code also comprises somesupplementary letters following the

other characters in order to addparticular information.For electrical switchgear, onlysupplementary letter W is used.It indicates a protection against badweather checked by other means thanthose specified for the secondcharacteristic numeral, which aredifficult to apply to large equipment.For instance, the spraying equipmentdesigned for dielectric wet tests is usedto check the weather proofing ofenclosed high voltage switchgear.

Letters M and S are used for rotatingmachines to indicate that they havebeen tested with the rotor in Movementor Stationary.

fig. 5: the ball penetrates but the test finger stays away from the live-part; it is therefore IP 1XB(according to IEC 529).

4. the IK code

introductionSome countries had felt the need alsoto codify the protection provided byenclosures against mechanicalimpacts.

To do that, they added a thirdcharacteristic numeral to the IP code(the case of Belgium, Spain, Franceand Portugal). But now that IEC 529has been adopted as a European

standard, no countries may have adifferent IP code.

Since IEC has so far refused to add thisthird numeral to the IP code, the onlypossibility keeping a code system inthis area has been to create a differentcode. This is the object of the Europeandraft standard prEN 50102: IK code.

Since the third numeral of the differentcountries might have different

meanings, and to introducesupplementary severity levels in orderto cover the main needs of ProductCommittees, the degrees of the IK codehave meanings different from the oldthird numerals (see appendix 2).

In order to limit confusion, each newdegree is indicated by a number of twonumerals.

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Cahier Technique Merlin Gerin n° 166 / p.10

IK code IK 01 IK 02 IK 03 IK 04 IK 05 IK 06 IK 07 IK 08 IK 09 IK 10

energy Joules 0.15 0.2 0.35 0.5 0.7 1 2 5 10 20

radius mm (1) 10 10 10 10 10 10 25 25 50 50

material (1) P P P P P P S S S Ssteel = S (2)polyamide = P (3)

pendulumhammer yes yes yes yes yes yes yes yes yes yes

springhammer yes yes yes yes yes yes yes no no no

verticalhammer no no no no no no yes yes yes yes

(1) of the striking element(2) Fe 490-2 according to ISO 1052, of hardness 50 HR to 58 HR to ISO 6508(3) of hardness HR 100 according to ISO 2039/2

fig. 6: test requirements for the various IK degrees.

fig. 7: spring-hammer (a) (according to IEC 68-2-63 and pendulum hammer (b) (according toIEC 68-2-62). Note that a calibration device not represented here is required.

degrees of protectionThe degrees of protection correspondto impact energy levels, given inJoules. An «impact», action of ahammer directly applied to theequipment must be distinguished froma «shock» transmitted by the supportand expressed in vibration terms i.e. infrequency and acceleration.

Figure 6 shows table 1 of the standardcompleted with information relevant totest means. In fact, the degrees ofprotection against mechanical impactscan be checked with different types ofhammers: a pendulum hammer, aspring hammer or a free fall hammer(see fig. 7). Each has a particular scopein energy and in direction of application.In order to get similar severity withimpacts of the same energy, certaincharacteristics of the test means haveto be complied with: the radius and thehardness of the striking element.

The product standard must specify onwhich parts the blows are to be appliedand what the acceptance criteria are.

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Cahier Technique Merlin Gerin n° 166 / p.11

5. application to the design of electrical equipment

These notions of protection have alarge influence on the design ofequipment because protection has tobe assessed not only by the externalenclosure, but also by internalenclosures or parts of internalenclosures (partitions, shutters, etc).Therefore the degree of protection ofpersons has to be defined also forinternal parts which can initiate a directcontact during an operation, forinstance when withdrawing a circuit-breaker. In addition, even if anenclosure provides the required degreeof protection, it is also necessary that it

cannot be removed partially or totally.The point does not concern pieces ofequipment such as motors,transformers, etc, but it is of primaryimportance for some compartments ofassemblies which have to beaccessible during servicing of theequipment.

Two kinds of compartments areconsidered in this case:■ those which are opened only rarely(bus bars) and for which bolted coverscan be considered as satisfactory.Opening them being not a simpleoperation, it is supposed that adequate

precautions dictated by safetyrequirements will be taken.

■ those which may have to be openedduring normal operation of theequipment. They are generally closedby doors which can be locked orblocked by an additional control systemwhich completes the protectionprovided by the enclosure.

During all these service andmaintenance operations the electricalcontinuity of the enclosure must not beinterrupted whatever the position of theequipment is.

6 . conclusion

To be satisfactory, any piece of equip-ment has to comply with its releventproduct standard. But this standard uses«horizontal» ones, particularly thoserelevant to the degree of protection.

The manufacturer as well as the usershould therefore refer to thecorresponding standards after readingthis «Cahier Technique»(see bibliography).

Cahier Technique Merlin Gerin n° 166 / p.12

appendix 1: correspondence between water-tests of the IP codeand water-tests of IEC 68-2-18

Réal. : Illustration Technique Lyon -DTE 01/93 - 2500 - Imp. Léostic

IP code IP X1 & 2 IP X3 & 4 IP X5 & 6 IP X7

water-tests ofIEC 68-2-18 test Ra2 test Rb2 test Rb3 test Rc1

appendix 2: equivalence between the old third numerals of thefrench IP code and IK code

old 3d numerals IP XX1 IP XX3 IP XX5 IP XX7 IP XX9of the IP code ofNF C 20-010(1986)

IK code IK 02 IK 04 IK 07 IK 08 IK 10

appendix 3: bibliography

Documents describing degrees ofprotection■ IEC 529 (1989-11): Degrees ofprotection provided by enclosures(IP code)■ ■ European application: EN 60529,■ ■ French application: NF C 20-010(1992).

■ prEN 50102 (1993): Degrees ofprotection provided by enclosures forelectrical equipment against externalmechanical impacts (IK code). Draft.

■ French application: prNF C 20-015(1993). Draft.

Documents specifying degrees ofprotection for switchgear■ Decret of the 14th of November 1988from the French government:Protection of workers against electricalcurrents.

■ HN 60-E-01 (1974) EDF: Specificationfor general rules relevant to plastic mate-rials used in electrical equipment for low-voltage networks and connecting points.

■ IEC 298 (1990): A.C.metal-enclosedswitchgear and controlgear for ratedvoltages above 1 kV and up to andincluding 52 kV.

■ ■ European application: HD 187,■ ■ French application: NF C 64-200.

■ IEC 439-1 (1985): Requirements fortype-tested and partially type-tested(low-voltage) assemblies.■ ■ European application: EN 60439,■ ■ French application: NF C 63-421.

■ IEC 947-1 (1988): Low-voltageswitchgear and controlgear.■ ■ European application: EN 60947,■ ■ French application: NF C 63-001.