iec 60815-2

36/191/CDCOMMITTEE DRAFT (CD)

IEC/TC or SC:36

Project numberIEC 60815-2 TS Ed. 1.0

Title of TC/SC:Insulators

Date of circulation2002-06-14

Closing date for comments2002-09-20

Also of interest to the following committees

Supersedes document36/153/NP & 36/157/RVN

Functions concerned: Safety EMC Environment Quality assurance

Secretary:Mr B Lester [email protected].

THIS DOCUMENT IS STILL UNDER STUDY AND SUBJECT TOCHANGE. IT SHOULD NOT BE USED FOR REFERENCE PURPOSES.RECIPIENTS OF THIS DOCUMENT ARE INVITED TO SUBMIT, WITHTHEIR COMMENTS, NOTIFICATION OF ANY RELEVANT PATENTRIGHTS OF WHICH THEY ARE AWARE AND TO PROVIDESUPPORTING DOCUMENTATION.

Title:Selection and dimensioning of high-voltage insulators for polluted conditions -Part 2: Ceramic and glass insulators for a.c. systems

(Titre) :

Introductory note

This document includes an introduction from the project leader (see page 5) covering the intent ofthe document, the planned schedule of work and the content and orientation of the revision of IEC60815: 1986.The first draft of part 1 of IEC 60815 has been circulated as 36/187/CD. This draft layout for Part 2is being circulated in order to allow the reader to see how the content of Part 1 will be applied andused in Parts 2 to 5.The values given for correction factors, limits etc. are still under discussion and are mostly given asexamples only; this is noted in the text. The statistical procedure for determining the parameters forconfirmation by artificial pollution tests is still under development by CIGRE WG33.13. Thisinformation should be available by the end of 2002.

Comments from the National Committees on the principle and layout of this draft are welcome andwill be passed on to the Working Group. Any technical proposals concerning the scope and effect ofprofile parameters would also be welcome.

TC 36 and WG 11 are meeting in Beijing in October. This document and comments received fromthe national committees will be considered at those meetings. It is intended that a second CD willbe issued after comments from the national committees have been considered by WG 11

FORM CD (IEC)2002-01-15

36/191/CD2

CONTENTS

FOREWORD........................................................................................................................... 3Introduction from the Project Leader ....................................................................................... 51 Scope and object..............................................................................................................62 Normative references ....................................................................................................... 63 Definitions ........................................................................................................................ 64 Abbreviations ................................................................................................................... 75 Principles ......................................................................................................................... 76 Material selection ............................................................................................................. 77 Site severity determination ............................................................................................... 78 Determination of the basic USCD ..................................................................................... 89 Choice of profile ............................................................................................................... 8

9.1 General recommendations for profiles (repeated from IEC 60815-1)........................ 89.2 Specific recommendations for profiles ..................................................................... 8

10 Correction of the basic USCD......................................................................................... 1310.1 Correction for profile suitability Kps ........................................................................ 1310.2 Correction for insulator diameter Kad ..................................................................... 1310.3 Correction for spacing versus shed overhang Ksp .................................................. 1310.4 Correction for creepage distance versus spacing Kld ............................................. 1310.5 Correction for shed overhang and spacing Kos....................................................... 1410.6 Correction for shed angle Kα ................................................................................. 1510.7 Correction for creepage factor Kcf.......................................................................... 15

11 Determination of the final minimum creepage distance ................................................... 1612 Confirmation by testing................................................................................................... 16

12.1 Determination of the co-ordination pollution severity withstand level ..................... 1612.2 Determination of the required pollution severity withstand level ............................. 16

12.2.1 Compensation factors................................................................................ 1612.3 Selection of the standard pollution withstand test type........................................... 1612.4 Test parameters and procedure............................................................................. 1712.5 Criteria of confirmation .......................................................................................... 17

FIGURES.............................................................................................................................. 17Annex A Bibliographic References ........................................................................................ 19

36/191/CD3

INTERNATIONAL ELECTROTECHNICAL COMMISSION

____________

IEC 60815: Selection and dimensioning of high-voltage insulators for pollutedconditions -

Part 2: : Ceramic and glass insulators for a.c. systems

FOREWORD1) The IEC (International Electrotechnical Commission) is a worldwide organization for standardization comprising all

national electrotechnical committees (IEC National Committees). The object of the IEC is to promote international co-operation on all questions concerning standardization in the electrical and electronic fields. To this end and in additionto other activities, the IEC publishes International Standards. Their preparation is entrusted to technical committees;any IEC National Committee interested in the subject dealt with may participate in this preparatory work. International,governmental and non-governmental organizations liaising with the IEC also participate in this preparation. The IECcollaborates closely with the International Organization for Standardization (ISO) in accordance with conditionsdetermined by agreement between the two organizations.

2) The formal decisions or agreements of the IEC on technical matters express, as nearly as possible, an internationalconsensus of opinion on the relevant subjects since each technical committee has representation from all interestedNational Committees.

3) The documents produced have the form of recommendations for international use and are published in the form ofstandards, technical specifications, technical reports or guides and they are accepted by the National Committees inthat sense.

4) In order to promote international unification, IEC National Committees undertake to apply IEC International Standardstransparently to the maximum extent possible in their national and regional standards. Any divergence between theIEC Standard and the corresponding national or regional standard shall be clearly indicated in the latter.

5) The IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for any equipmentdeclared to be in conformity with one of its standards.

6) Attention is drawn to the possibility that some of the elements of this technical specification may be the subject ofpatent rights. The IEC shall not be held responsible for identifying any or all such patent rights.

The main task of IEC technical committees is to prepare International Standards. In exceptionalcircumstances, a technical committee may propose the publication of a technical specification when

• the required support cannot be obtained for the publication of an International Standard, despiterepeated efforts, or

• The subject is still under technical development or where, for any other reason, there is thefuture but no immediate possibility of an agreement on an International Standard.

Technical specifications are subject to review within three years of publication to decide whetherthey can be transformed into International Standards.

IEC 60815-2, which is a technical specification, has been prepared by technical committee 36:Insulators.

The text of this technical specification is based on the following documents:

Enquiry draft Report on voting

XX/XX/DTS XX/XX/RVC

Full information on the voting for the approval of this technical specification can be found in thereport on voting indicated in the above table.

This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.

The committee has decided that the contents of this publication will remain unchanged until ______.At this date, the publication will be

• reconfirmed;• withdrawn;

36/191/CD4

• replaced by a revised edition, or• amended.

36/191/CD5

Introduction from the Project Leader

The revision of IEC 60815:1986 to take into account current experience, knowledge and practicerelated to polluted insulators in general, and specifically to include polymer insulators and to coverd.c. systems, requires subdivision of the guide into the following five parts:

Part 1: Definitions, information and general principlesPart 2: Ceramic and glass insulators for a.c. systemsPart 3: Polymer insulators for a.c. systemsPart 4: Ceramic and glass insulators for d.c. systemsPart 5: Polymer insulators for d.c. systems

As work on part 1 has progressed, it has become evident that the requirements for evaluation andmeasurement of site severity were a major concern. The content of part 1 now principally coverssite pollution severity determination, description of the flashover mechanism, approaches forselection and dimensioning and testing techniques. The first draft of part 1 of IEC 60815 has beencirculated as 36/187/CD

This draft layout for Part 2 is being circulated in order to allow the reader to see how the content ofPart 1 will be applied and used in Parts 2 to 5.

The basic principle of selection has changed with respect to IEC 60815:1986 in that it is no longer asimple GO/NO-GO process. The reader of this draft will discover that the information gathered onthe pollution at the projected site (from IEC 60815-1) is used to determine a basic creepagedistance, which is then corrected as a function of the suitability of candidate insulators for the typeof pollution. Other factors, which take into account the influence of profile parameters (e.g.diameter, shed spacing etc.), are also applied to this creepage distance.

Additionally the user of the publication is now given means by which the selection process can beconfirmed – with a given degree of confidence – by use of relatively simple artificial pollutionwithstand test.

It is hoped that this revision of IEC 60815 will also result in the reduction of risk of over-design, inmore freedom in designing insulators for specific pollution problems or for unusual geometricconstraints and in a better comprehension of the factors affecting the behaviour of insulation inpolluted conditions.

The values given for correction factors, limits etc. are still under discussion and are mostly given asexamples only; this is noted in the text. The statistical procedure for determining the parameters forconfirmation by artificial pollution tests is still under development by CIGRE WG33.13. Thisinformation should be available by the end of 2002.

Comments from the National Committees on the principle and layout of this draft are welcome andwill be passed on to the Working Group. Any technical proposals concerning the scope and effect ofprofile parameters would also be welcome.

36/191/CD6

IEC 60815: Selection and dimensioning of high-voltage insulators for pollutedconditions -

Part 2: : Ceramic and glass insulators for a.c. systems

1 Scope and object

This guide is applicable to the selection of ceramic and glass insulators for a.c. systems, and thedetermination of their relevant dimensions, to be used in high voltage systems with respect topollution.

NOTE Ceramic and glass insulators have an insulating part manufactured either of glass or porcelain, whereas theinsulating surface of polymeric insulators is manufactured of polymers or other organic materials.

This part of IEC 60815 gives specific guidelines and principles to arrive at an informed judgementon the probable behaviour of a given insulator in certain pollution environments.

This structure is based on that used in CIGRE 33.13 TF 01 documents [1, 2], which form a usefulcomplement to this guide for those wishing to study in greater depth the performance of insulatorsunder pollution.

This guide does not deal with the effects of snow or ice on polluted insulators. Although this subjectis dealt with by CIGRE [3], current knowledge is very limited and practice is too diverse.

The aim of this guide is to give the user means to:

• Determine the basic Unified Specific Creepage Distance from Site Pollution Severity;• Choose appropriate profiles;• Apply correction factors for altitude, insulator shape, size and position etc. to the basic USCD.

2 Normative references

The following referenced documents are indispensable for the application of this document. Fordated references, only the edition cited applies. For undated references, the latest edition of thereferenced document (including any amendments) applies.

IEC 60507 Artificial pollution tests on high voltage insulators to be used on a.c. systems

IEC 60815-1 Selection and dimensioning of high-voltage insulators for polluted conditions - Part1: Definitions, information and general principles

IEC 61245 Artificial pollution tests on high-voltage insulators to be used on d.c. systems

3 Definitions

For the purpose of this publication, the following definitions apply. The definitions given below arethose which either do not appear in IEC 60050(471) or differ from those given in IEC 60050(471)

3.1Unified Specific Creepage Distance (repeated from IEC 60815-1 for clarity)The creepage distance of an insulator divided by the r.m.s. value of the highest operating voltageacross the insulator. It is generally expressed in mm/kV.NOTE This definition differs from that of Specific Creepage Distance where the phase-to-phase value of the highestvoltage for the equipment is used. For phase to ground insulation, this definition will result in a value that is √3 times thatgiven by the definition of Specific Creepage Distance in IEC 815 (1986).

3.2Basic Unified Specific Creepage DistanceThe initial value of Unified Specific Creepage Distance for a pollution site before correction for size,profile mounting position etc. according to this publication.

36/191/CD7

4 Abbreviations

ALS Alternating Long/Short ShedsSPS Site Pollution SeverityUSCD Unified Specific Creepage DistanceTo be completed …

5 Principles

The overall process of insulation selection and dimensioning can be summarised as follows:

Firstly, using IEC 60815-1:

• Determination of the appropriate approach A, B or C as a function of available knowledge, timeand resources;

• Collection of the necessary input data, notably whether a.c. or d.c. energisation, system voltage,insulation application type (line, post, bushing etc.);

• Collection of the necessary environmental data, notably site pollution severity and class;

• Preliminary choice of possible candidate insulators suitable for the environment;

Then, using this publication:

• Refining choice of possible candidate ceramic or glass insulators suitable for the environment;

• Determination of the basic Unified Specific Creepage Distance for the insulator types andmaterials, either using the indications in the this Publication, or from service or test stationexperience in the case of Approach A;

• Modification, where necessary, of the basic USCD by factors depending on the size, profile,orientation etc. of the candidate insulator;

• Verification of the dimensioning, in the case of Approach B, by laboratory tests (see annex A).

6 Material selection

To select suitable insulators from catalogues based on the system requirements and theenvironmental conditions, three approaches (A, B, C in IEC 60815-1) are recommended. Whateverthe approach which is chosen, The input data includes the type of insulator material. In the case ofceramic and glass insulators there is no significant difference in pollution behaviour between thematerials. Therefore the choice of either glass or ceramic material with respect to the other dependspurely on factors which are out of the scope of this publication.

7 Site severity determination

For the purposes of standardisation, five classes of pollution characterising the site severity arequalitatively defined in IEC 60815-1, from very light pollution to very heavy pollution, as follows:

a – Very lightb – Lightc – Mediumd – Heavye – Very heavy.

NOTE These letter classes do not correspond directly to the previous number classes of IEC 60815:1986.

The SPS class for the site is determined according to IEC 60815-1 and is used to determine thebasic USCD for glass and ceramic insulators.

36/191/CD8

8 Determination of the basic USCD

Figure 1 shows the relation between SPS class and basic USCD for glass and ceramic insulators.The values shown are preferred values representative of mid-class SPS. If exact SPSmeasurements are available, it is recommended to take a basic USCD which corresponds to theposition of the SPS measurements within the class. For example the example E6 given in figure 5 ofIEC 60815-1 would have a basic USCD of 47 mm/kV.

NOTE – It is assumed that the final USCD resulting from the application of the corrections given hereafter to the basicUSCD will not correspond exactly to a creepage distance available for catalogue insulators. Hence it is preferred to workwith exact figures and to round up to an appropriate value at the end of the correction process.

9 Choice of profile

9.1 General recommendations for profiles (repeated from IEC 60815-1)

Aerodynamic or open profiles prove to be beneficial in areas where the pollution is deposited ontothe insulator by wind, such as deserts, heavily polluted industrial are as or coastal areas whichare not directly exposed to salt spray. This type of profile is especially effective in areas that arecharacterised by extended dry periods. Open profiles are also accessible for easy cleaning undermaintenance.

The use of steep anti fog profiles or shed profiles with deep under-ribs, are beneficial in areasexposed to a salt water fog or spray, or to other pollutants in the dissolved state. These profilesmay also be effective in areas with a particulate pollution precipitation containing slow dissolvingsalts.

More recent flatter anti-fog profiles with fewer or shallower under-ribs can be beneficial in areas ofheavy industrial pollution, notably where string length is limited; however deep under-ribs should beavoided on horizontal insulators.

Alternating long and short sheds are beneficial in areas where heavy wetting can occur.

Standard profiles are effective for use in 'very light' to 'medium' polluted areas where a longcreepage distance or aerodynamically effective profile is not required.

9.2 Specific recommendations for profiles

The following tables give specific recommendations for insulator profiles. In each case thesuitability of each profile for use in specific areas is given as recommended, acceptable orunsuitable.

The choice of profiles is often not determined by pollution alone. The insulator material, design,manufacturing process or application may preclude certain profiles. Hence the optimal profile maynot be available for the combination of insulator/pollution type. Therefore the choice or use of an"unsuitable" profile is not excluded. Correction for the profile suitability is given in clause 10.1.Figures 2 to 4 show typical profiles.

(PL Note : These tables are not finalised)

36/191/CD9

Table 1 – The selection of profile for vertical a.c. cap and pin insulators

Polluted areas Open profile Standard profile Fog-type profile

Desert

Areas with sandy soils or ina desert location.

These areas can beextensive. Pollution thatdissolves slowly has a highinert component, mainlywind borne.

Collects less pollution, asthe aerodynamic profilegives good self-cleaning bywind.

Shallow under ribscollect wind-bornedeposits.Needs a relatively longstring length.

More wind borne depositaccumulates on theunder-side due to reducedself cleaning

Coastal

Areas in direct vicinity of thecoast, but in some casescan be as far inland as 10-20 km inland.

Rapid pollution build-up andeffective washing (not veryadhesive)

Quick dissolving pollution

Has low inert component

Pollution by wind andgravity.

Collects less pollution, asthe aerodynamic profilegives good self-cleaning bywetting and offshore wind.


More wind borne depositaccumulates on theunder-side due to reducedself-cleaning.

Deep under-rib preventswetting of whole underside during rain

Long creepage distanceper disc.

Industrial / Agriculture

Areas in close proximity tothe industrial pollutionsource, may only affect afew installations.

Conductive particulate pollu-tion.(Cement, coal,chemicals, NOx, SOx etc,)

Pollution that dissolvesslowly, has medium or highinert component, oftenheavy particles which settleon horizontal surfaces.

Large upper surfacecollects more pollutiondeposit

Pollution not readilyremoved


Underside collects wind-borne deposit.

Deep under-rib preventswetting of whole underside during rain.

Long creepage distanceper disc.

Inland (Low pollution)

No advantage provided bythe open profile.

The added creepage isunnecessary

Notes:

Recommended

Acceptable

Unsuitable

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Table 2 – The selection of profile for horizontal a.c. cap and pin insulators

Polluted areas Open profile Standard profile Fog-type profile

Desert



Collects less pollution asthe aerodynamic profilegives good self-cleaningby wind.

Shallow ribs collect wind-borne deposits.Needs a relatively longstring length.

More wind borne depositaccumulates on the sidecontaining ribs due toreduced self cleaning

Coastal




has low inert component


Collects less pollution, asthe aerodynamic profilegives good self-cleaningby wetting and off-shorewind.

Total surface becomespolluted but is accessiblefor natural cleaning

Needs relatively longstring length.

Total surface becomes pol-luted and natural cleaning isnot so effective.

Longer creepage withinlimited string length





Very small horizontalsurface reduces pollutiondeposit. Easier to clean.

Total surface becomespolluted but is accessiblefor natural cleaning

Needs relatively longstring length.

Deep ribs collect pollutionand do not self-clean.

Longer creepage withinlimited string length.


No advantage providedby the open profile.

The added creepageunnecessary

Notes:

Recommended

Acceptable

Unsuitable

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Table 3 – The selection of profile for vertical and horizontal a.c. long rod and post insulators

Polluted areas Plain profile Alternating shed a) Fog-shape profile

Desert



With small shedinclination

Coastal




Has low inert component






All others

If slow dissolving salts arepresent




Notes

a) An alternating shed profile may have an advantage under heavy wetting conditions.The pollution deposit on hollow and post insulators reduces with increasing diameter. However, the pollution flashovervoltage reduces with increasing diameter.The shed profile parameters are assumed to be close to, or as per IEC 60815.

Recommended

Acceptable

Unsuitable

36/191/CD12

Table 4 – The selection of profile for vertical ceramic a.c. hollow insulators

Polluted areas Plain profile Alternating shed a) Fog-shape profile

Desert



Collects less pollution asthe aerodynamic profilegives good self-cleaning bywind. Needs relatively longcreepage

Collects less pollution asthe aerodynamic profilegives good self-cleaningby wind

More wind borne depositaccumulate on the under-side due to reduced self-cleaning.

Coastal




has low inert component


Total surface becomespolluted and can easily betotally wetted

Needs a relatively longcreepage.

Total surface becomespolluted and but isaccessible for naturalcleaning.

More wind borne depositaccumulate on the under-side due to reduced self-cleaning

Deep under-rib preventswetting of whole underside.

Longer creepage withinlimited length



Conductive particulate pollu-tion. (Cement, coal,chemicals, NOx, SOx etc,)


Large upper surfacecollects more pollutiondeposit.

Pollution does not cleaneasily.

Needs a relatively longcreepage

Under side collectspollution and does notself-clean

Deep under-rib preventswetting of whole underside.

Longer creepage withinlimited length

If slow dissolving salts arepresent


Diameter influence The added creepageunnecessary

Notes:

a) An alternating shed profile may have an advantage under heavy wetting conditionsThe pollution deposit on hollow and post insulators reduces with increasing diameter. However, the pollution flashovervoltage reduces with increasing diameter.The shed profile parameters are assumed to be close to or as per IEC 60815

Recommended

Acceptable

Unsuitable

36/191/CD13

10 Correction of the basic USCD

The following corrections shall be applied to the basic USCD where applicable. All the factors aremultipliers.

(PL NOTE: The values and applicability of the correction factors are not finalised)

10.1 Correction for profile suitability Kps

Recommended profile:Kps = 0,8Acceptable profile: Kps = 1,0Unsuitable profile: Kps = 1,25

10.2 Correction for insulator diameter Kad

For long rod, post and hollow core insulators correct for average diameter Dm by:

Kad = 0,001Da + 0,7Where Da = (2Dt + Ds1 +Ds2)/4 (Ds1=Ds2 for plain sheds)

Ds2

Ds1

Dt

0,6

0,7

0,8

0,9

1

1,1

1,2

1,3

1,4

1,5

1,6

0 100 200 300 400 500 600 700 800 900

Average diameter (mm)

Kad

10.3 Correction for spacing versus shed overhang Ksp

Not applicable to cap and pin insulators or multi-shed pin insulators

s

p

0,8

0,9

1

1,1

1,2

1,3

1,4

1,5

0,4 0,5 0,6 0,7 0,8 0,9 1s/p

Ksp

10.4 Correction for creepage distance versus spacing Kld

d is the straight air distance between two points on the insulating part or between apoint on the insulating part and another on a metal part.

36/191/CD14

l is the part of the creepage distance measured between the above two points.l/d is the highest ratio found on any section, for example on the underside of a capand pin insulator.

l d

l

d

0,8

0,9

1

1,1

1,2

1,3

1,4

1,5

1,6

0 2 4 6 8

l/d

Kld

10.5 Correction for shed overhang and spacing Kos

Not applicable to cap and pin insulators.

c p2

p1

0,8

0,85

0,9

0,95

1

1,05

1,1

1,15

1,2

1,25

1,3

0 10 20 30 40 50p1 -p2 (mm)

Kos

c ≥ 50

30 < c <50

c ≤ 30

36/191/CD15

10.6 Correction for shed angle Kαααα

α

0,80,850,9

0,951

1,051,1

1,151,2

1,251,3

0 10 20 30 40Alpha °

Kα ααα

10.7 Correction for creepage factor Kcf

CF is equal to l/S where:

l is the total creepage distance of the insulator

S is the arcing distance of the insulator

For cap and pin insulators CF is determined for a string of 5 insulators or more.

0,8

0,9

1

1,1

1,2

1,3

1,4

1,5

1,6

3 3,5 4 4,5 5CF

Kcf

SPS class a

SPS class e

36/191/CD16

11 Determination of the final minimum creepage distance

Once the basic USCD has been corrected according to clause 10, the final minimum creepagedistance is determined for the candidate insulator by rounding up to the nearest creepage distanceavailable for that type of insulator within the constraints (system, dimensional etc.).

For example a final USCD of 36,5 mm/kV is found for a certain candidate cap and pin insulator. Thesystem maximum phase-to-ground voltage is 228 kV. The required minimum creepage distance istherefore 228 x 36,5 = 8322 mm. The creepage distance of each cap and pin insulator unit is 380mm, requiring 21,9 units. Therefore the final minimum creepage distance will be 22 x 380 = 8360mm.

12 Confirmation by testing

(PL NOTE: The information necessary for the complete description of the procedure for confirmationby testing is currently under discussion in CIGRE 33.13. This information should be available by theend of 2002.)

12.1 Determination of the co-ordination pollution severity withstand level

The determination of the co-ordination pollution severity withstand level consists of determining thelowest value of the withstand severity of the insulation which will meet the performance criterionwhen it is subjected to the highest voltage for the equipment.

The co-ordination pollution severity withstand level is obtained by multiplying the site pollutionseverity by a co-ordination factor. The value of the co-ordination factor depends on the accuracy ofthe evaluation of the site pollution severity and whether an empirical or statistical appraisal of thedistribution of the pollution severity, the insulator characteristics and the required performancecriterion are used.

12.2 Determination of the required pollution severity withstand level

The determination of the required pollution severity withstand level consists of converting the co-ordination pollution severity withstand level to the appropriate conditions for the standard pollutionwithstand test. This is accomplished by multiplying the co-ordination pollution severity withstandlevel by factors which compensate for the differences between the actual in-service conditions ofthe insulation and those in the standard withstand tests.

12.2.1 Compensation factors

The factors described hereafter compensate for:

• Differences in pollution catch of the insulator used for the site pollution severity measurementand the insulator to be tested;

• Differences in the uniformity of the pollution deposit at site and in the test;• Differences in the wetting conditions in service and those during the test;• Differences in energisation of the insulator used for the site pollution severity measurement and

the insulator to be tested;• The differences in the equipment assembly;• The dispersion in the product quality;• The statistical uncertainty of performing a limited number of tests to verify the required pollution

severity withstand level;• Other influences of importance.

(PL NOTE: To be completed with a description of the determination of the factors above)

12.3 Selection of the standard pollution withstand test type

The relevant test method to be used is selected according to the type of pollution at the site, thetype of insulator and the type of energisation. The tests given in IEC 60507 are directly applicableto ceramic and glass insulators for a.c. systems.

36/191/CD17

As a general rule, the solid layer test is recommended for type A pollution and the salt-fog test fortype B pollution.

The applicability of the required pollution severity withstand level to a specific site is:

• dependent on whether the test method used can be considered representative of the intendedenvironment and;

• restricted by the approximation and limitations inherent to the chosen laboratory test method.(PL NOTE: To be completed with a more information on choosing the appropriate test)

12.4 Test parameters and procedure

(PL NOTE: To be completed)

12.5 Criteria of confirmation

(PL NOTE: To be completed)

FIGURES

22

28

35

44

55

20

25

30

35

40

45

50

55

60

a b c d eSPS Class

Bas

ic U

SCD

(mm

/kV)

Figure 1 – Basic USCD as a function of SPS class

a) Plain Shed b) Alternating Shed (ALS) a) Under ribbed ShedFigure 2 – Typical ceramic post, long rod and hollow insulator shed profiles

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a) Standard Disc Shed b) Aerodynamic Disc Shed

c) "Steep" Anti-Fog Disc Shed d) "Flatter" Anti-Fog Disc Shed

Figure 3 – Typical cap and pin shed profiles

c) Single-piece pin insulator d) Multi-piece pin insulatorFigure 4 – Typical pin type shed profiles

36/191/CD19

Annex A Bibliographic References

1 CIGRE Taskforce 33.04.01 – “Polluted insulators: A review of current knowledge”, CIGREbrochure N° 158-2000

2 CIGRE Taskforce 33.13.01 – Guidelines for the selection and dimensioning of insulators foroutdoor applications, CIGRE brochure N° ???-2003

3 CIGRE Taskforce 33.13.07 – "Influence of Ice and snow on the flashover performance ofoutdoor insulators Part 1 Effects of Ice", ELECTRA No. 187 December 1999, and Part 2"Effects of Snow", ELECTRA No. 188 February 2000.

4 CIGRE Taskforce 33.04.03 – “Insulator pollution monitoring”, Electra 152, February 1994---

© International Electrotechnical Commission, IEC

iec 60815-2

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