iso_v_05

FachgebietHochspannungstechnik

Overvoltage Protection and Insulation Coordination / Chapter 1 - 1 -

Overvoltage ProtectionandInsulation Coordinationin Power Systems

Prof. Dr.-Ing. Volker HinrichsenDipl.-Ing. Simona Feier-Iova

Technische Universität DarmstadtHigh Voltage Laboratories

© Siemens



What is Insulation Coordination?

Definition in IEC 60071-1Definition in IEC 60071-1

Definition in IEEE 1313.1Definition in IEEE 1313.1



Fundamentals of Insulation Coordination

Time duration of (over-)voltage

Possible voltages without arresters

Voltages limited by arresters

Withstand voltage of equipment

Lightning overvoltages(Microseconds)

Switching overvoltages(Milliseconds)

Temporary overvoltages(Seconds)

Highest voltage of equipment(Continuously)

Mag

nitu

deof

(ov

er-)

volta

ge/ p

.u.

1

2

3

4

0

5



What is Insulation Coordination?

Procedure of insulation coordination [THI-01]

Three elements are involved in the insulation coordination discipline, namely:

• the study of the "stresses" , both electrical and environmental, acting on the equipment insulation. This is usually performed by calculations or field measurements;

• the study of the "strength" (dielectric withstand characteristics) of the insulation (both new and aged) when submitted to such stresses, taking into account, when applicable, the effect of the environmental stresses (pollution, rain, snow, ice, atmospheric conditions at large altidudes), including the study of the "test and measurement techniques" which are employed to assess such strength. The strength is determined by calculations, based on suitable discharge models, and/or by laboratory/factory tests, on-site tests and in-service measurements (diagnostics);

• the assessment of the insulation performance (usually expressed in terms of risk of failure) in the considered situation of stresses and strength, including the selection and application of "protective devices and techniques", to establish the final insulation design fulfilling the specified requirements. This may be based on "deterministic" or "statistical" approach.

Three elements are involved in the insulation coordination discipline, namely:

• the study of the "stresses" , both electrical and environmental, acting on the equipment insulation. This is usually performed by calculations or field measurements;

• the study of the "strength" (dielectric withstand characteristics) of the insulation (both new and aged) when submitted to such stresses, taking into account, when applicable, the effect of the environmental stresses (pollution, rain, snow, ice, atmospheric conditions at large altidudes), including the study of the "test and measurement techniques" which are employed to assess such strength. The strength is determined by calculations, based on suitable discharge models, and/or by laboratory/factory tests, on-site tests and in-service measurements (diagnostics);

• the assessment of the insulation performance (usually expressed in terms of risk of failure) in the considered situation of stresses and strength, including the selection and application of "protective devices and techniques", to establish the final insulation design fulfilling the specified requirements. This may be based on "deterministic" or "statistical" approach.



Literature (1)

[BAL-04-1] G. BalzerPower Systems, Part 2Chapter 4: Insulation coordinationScript TU Darmstadt, 2004

[BAL-04-2] G. BalzerElektrische Energieversorgung, Teil 2Kapitel 4: IsolationskoordinationSkript der TU Darmstadt, 2004

[CIG-73] CIGRE W.G. 13-02Switching overvoltages in EHV and UHV systems with special referenceto closing and reclosing transmission linesELECTRA 30 (1973) pp. 70-122

[CIG-79-1] CIGRE WG 33.02Phase-to-phase Insulation Co-ordination:Part 1: Switching overvoltages in three-phase systemsELECTRA 64 (1979) pp. 138-158

[CIG-79-2] CIGRE WG 33.03Phase-to-phase Insulation Co-ordinationPart 2: Switching impulse strength of phase-to-phase external insulationELECTRA 64 1979, pp. 158-181



Literature (2)

[CIG-79-3] CIGRE WG 33.06Phase-to-phase Insulation Co-ordinationPart 3: Design and testing of phase-to-phase insulationELECTRA 64 1979, pp. 182-210

[CIG-79-4] CIGRE TF 33-03.03Phase-to-phase Insulation Co-ordinationPart 4: The influence of non-standard conditions on the switching impulse strengthof phase-to-phase insulationELECTRA 64 1979, pp. 211-230

[CIG-91] CIGRE WG 33.01Guide to procedures for estimating the lightning performance oftransmission lines, CIGRE technical brochure No. 63, 1991buch_020.pdf

[CIG-92] CIGRE WG 33-07Guidelines for the evaluation of the dielectric strength of externalinsulation, CIGRE technical brochure No. 72, 1992buch_019.pdf

[DOR-81] H. DorschÜberspannungen und Isolationsbemessung bei Drehstrom-HochspannungsanlagenSiemens AG, Erlangen, 1981 (ISBN 3-8009-1325-9)



Literature (3)

[ERI-88] A.J. Eriksson, K.-H. WeckSimplified procedures for determining representative substation impinging lightningovervoltages, CIGRE report 33-16, 1988

[ETG-93] ETG-Fachbericht 49ETG-Tage '93: Isolationskoordination in Hoch- und Mittelspannungsanlagenvde-Verlag GmbH Berlin, Offenbach (ISBN 0341-3934)

[FGH-78] FGH Technischer Bericht 1-240Isolationskoordination auf der Grundlage der neuen DIN/VDE-Bestimmung 0111FGH, Mannheim, Juli 1978

[HIL-99] A. R. HilemanInsulation Coordination for Power SystemsMarcel Dekker, Inc., New York, Basel, 1999

[HIN-00] V. HinrichsenMetalloxidableiter: GrundlagenSiemens AG Berlin, 1. Auflage 2000AbleiterBuch.pdf

[HIN-01] V. HinrichsenMetalloxidableiter: GrundlagenSiemens AG Berlin, Edition 1, 2001ArresterBook.pdf



[HIN-03] V. HinrichsenLatest Designs and Service Experience with Station-Class Polymer Housed Surge ArrestersWorld Conference on Insulators, Arresters & BushingsMarbella (Málaga), Spain, November 16-19, 2003, Proceedings pp. 85-96pub_048.pdf

[KIN-05] V. HinrichsenLatest Testing Requirements and Emerging Standards for Transmission Line ArrestersWorld Conference on Insulators, Arresters & BushingsHong Kong, November 27-30, 2005inmr_2005_paper.pdf

[KIS-84] I. Kishizima, K. Matsumoto, Y. Watanabe, New facilities for phase switching impulsetests and some test results, IEEE PAS TO3 No. 6, June 1984 pp. 1211-1216.

[KOE-93-1] D. König, Y. N. RaoTeilentladungen in Betriebsmitteln der Energietechnikvde-Verlag, Berlin, Offenburg, 1993, ISBN 3-8007-1764-6

[KOE-93-2] D. König, Y. N. RaoPartial discharges in Power Apparatusvde-Verlag, Berlin, Offenburg, 1993, ISBN 3-8007-1760-3

Literature (4)



[PAR-68] L. Paris, R. CortinaSwitching and lightning impulse discharge characteristics of large air gaps and long insulationstrings, IEEE Trans on PAS, vol 87, No. 4, April 1968, p. 947-957

[RUD-99-1] R. Rudolph, B. RichterDimensioning, testing and application of metal oxide surge arresters in medium voltage networks 3rd Edition, 1999, ABB Switzerland, 26 pages (also available in German)application_guide_medium_voltage_networks.pdf

[RUD-99-2] R. Rudolph, B. RichterBemessung, Prüfung und Einsatz von Metalloxid-Ableitern in MittelspannungsnetzenABB Schweiz AG, Wettingen (CH), 3. Auflage 1999Anwendungsrichtlinien_Mittelspannung.pdf

[THI-01] L. ThioneInsulation coordination in electrical power systems – theory and applicationTutorial, ALPI, Milan, 2001 (www.alpiass.com)buch_018.pdf

Literature (5)



[WEC-07] K.-H. WeckStandardization of insulation withstand levels for UHV systems inIEC TC 28 „Insulation co-ordination”IEC/CIGRE UHV Symposium Beijing 18-21 July 2007, report 5-45-4_KHWeck.pdf

Overview on CIGRE publications (very interesting!): Cigré Catalogue of Publications 01/07/2005CATALOGUE_PUBLICATIONS_2005.pdf

Literature (6)



IEC 60071-1, Edition 8.0 (2006-01)Insulation co-ordination – Part 1: Definitions, principles and rules

IEC 60071-2, Third Edition (1996-12)Insulation co-ordination – Part 2: Application guide

IEC/TR 60071-4, First Edition (2004-06)Insulation co-ordination - Part 4: Computational guide to insulation co-ordination and modelling of electrical networks

IEC 60099-4, Ed. 2.1, 2006-07Surge arresters – Part 4: Metal-oxide surge arresters without gaps for a.c. systems

IEC 60099-5, Ed. 1.1, 2000-03Surge arresters – Part 5: Selection and application recommendations

DIN EN 60071-1, 1996-07Isolationskoordination - Teil 1: Begriffe, Grundsätze und Anforderungen (IEC 60071-1:1993); Deutsche Fassung EN 60071-1:1995

DIN EN 60071-2, 1997-09Isolationskoordination - Teil 2: Anwendungsrichtlinie (IEC 60071-2:1996); Deutsche Fassung EN 60071-2:1997

IEEE 1313.1-1996IEEE Standard for Insulation Coordination—Definitions, Principles, and Rules

Standards (1)



IEEE 1313.2-1999IEEE Guide for the Application of Insulation Coordination

IEEE C62.11-2005IEEE Standard for Metal-Oxide Surge Arresters for AC Power Circuits (> 1 kV)

IEEE C62.22-1997IEEE Guide for the Application of Metal-Oxide Surge Arresters for Alternating-Current Systems

Standards (2)



Organization

Lecture 1331.01.200813

Test procedures; condition monitoring (life time aspects, partial discharges, non-conventional approaches)

Lecture 1224.01.200812

Calculation ExamplesLecture 1117.01.200811

Insulation coordinationLecture 1010.01.200810

Christmas holidays03.01.2008

Christmas holidays27.12.2007

Insulation coordinationLecture 920.12.20079

pollution, rain, parallel insulation, aging)Lecture 813.12.20078

Dielectric strength (incl. gap factors,Lecture 706.12.20077

Overvoltage protection incl. protective distanceLecture 629.11.20076

Traveling wavesLecture 522.11.20075

Lecture 415.11.20074

cancelled08.11.2007

Lecture 301.11.20073 Voltage stresses

in power systems

Lecture 225.10.20072

IntroductionLecture 118.10.20071



Organization

ExaminationExamination

Exclusively oral

ExercisesExercises

None; but calculation examples in the lecture

ScriptScript

Slides will be available for download

www.hst.tu-darmstadt.de

User: studentisoPW: isows0708



Insulation Coordination - Principles

Environment

Sys

tem System voltages

DielectricstrengthE

quip

men

t

Overvoltageprotection devices stress

versusstrength




• Voltages of the system– Nominal voltage Un

» rounded value for characterizing the system» 10 kV - 20 kV - 110 kV - 220 kV - 380 kV

– System voltage

» voltage at which the system is being operated» around the nominal value, but not constant

– Highest system voltage Us

» highest operating voltage between phases under norm al conditions» 12 kV - 24 kV - 123 kV - 245 kV - 420 kV (IEC 60038)

• Voltages of equipment– Highest voltage for equipment Um

» highest voltage between phases for which the insula tion is designed » 12 kV - 24 kV - 123 kV - 245 kV - 420 kV (IEC 60071-1)




• Overvoltages– voltages exceeding the peak value of the highest system voltage

– various amplitudes and shapes depending on» system configuration (grid size, degree of meshing, etc.)» origin of overvoltage (failure, switching, lightnin g strike etc.)

• Dielectric strength of insulation– verified by type test in the laboratory with the help of

» standardized test voltages (shape, amplitude)» specified test setups» specified environmental conditions

• Insulation coordination– Determination of interdependence between voltages and

overvoltages of the system and necessary test voltages for the equipment in the laboratory




Equipment inthe laboratoryEquipment inthe laboratory

Equipment inthe system

Equipment inthe system

Variety of amplitudes andshapes of overvoltages

Variety of amplitudes andshapes of overvoltages

Standardized amplitudesand shapes of test voltagesStandardized amplitudes

and shapes of test voltages

Variety of operatingconditions and age

Variety of operatingconditions and age

Standardized setupsand conditions

Standardized setupsand conditions

Variety of environmental conditions

Variety of environmental conditions

Standardizedenvironmental conditions

Standardizedenvironmental conditions




line

bb 1

bb 2

busbar disconnectors

Insulation phase - groundstressed by voltages between one phase and ground

1

Insulation phase - phasestressed by voltages between two phases

2

Longitudinal insulationstressed by voltages between same phases oftwo different systems

3

2

3

1



Insulation Coordination according to IEC 60071-1 (and 60071-2)




Procedure forinsulation

coordination= 10 pages!

Procedure forinsulation

coordination= 10 pages!

...39 pages in sum...39 pages in sum




...125 pages in sum...125 pages in sum



Procedure for Insulation Coordination - General

The procedure for insulation coordination consists of the selection of a set of standard withstand voltages which characterize the insulation of the equipment.

Range I Range II



Procedure for Insulation Coordination - General

Basic difference between ranges I and IIw

ithst

and

volta

ge

time duration of stresspeak

gap spacing 3 m

gap spacing 0.5 m

[FGH-78]

Minimum of withstand voltage for switching overvoltage

Minimum of withstand voltage for switching overvoltage

Withstand voltage continuously decreasing with time duration of stress

Withstand voltage continuously decreasing with time duration of stress

Range IRange I

Range IIRange II



Procedure for Insulation Coordination in Four Steps

Determination of the representative overvoltages Urp

• The representative overvoltages are derived from real service conditions, but have just standardized shapes.

• They are determined in amplitude, shape and duration by system analysis, taking into account overvoltage limiting devices.

[IEC 60071-1]



Determination of the coordination withstand voltage s Ucw

• The coordination withstand voltages are the lowest values of withstand voltages of each overvoltage class, for which the expected low failure rate of the equipment is not exceeded over its full lifetime.

• Derived from the representative overvoltages Urp by the coordination factor Kc.

[IEC 60071-1]


Typical for Germany:0.1% per year� 1 failure in 1000 years




Deterministic approachDeterministic approach Statistical approachStatistical approach

Assumed maximumof representative overvoltage

Assumed maximumof representative overvoltage

Multiplication by coordinationfactor based on

operating experience

Multiplication by coordinationfactor based on

operating experience

Statistical distribution of representative overvoltagesStatistical distribution of

representative overvoltages

Determination offailure probability of insulation

Determination offailure probability of insulation

Calculation of failure riskdepending on assumed

coordination withstand voltage

Calculation of failure riskdepending on assumed

coordination withstand voltage

Coordination withstand voltageAssumed conventional Ucw (0% value) Statistical Ucw (10% value)

Coordination withstand voltageAssumed conventional Ucw (0% value) Statistical Ucw (10% value)



Determination of the required withstand voltages Urw

• The required withstand voltages are determined by converting the coordination withstand voltages to appropriate standard test conditions.

• Usually different from the coordination withstand voltages.• Derived from the coordination withstand voltages Ucw by the safety factor Ks and the

atmospheric correction factor Kt or the altitude correction factor Ka.

[IEC 60071-1]




[IEC 60071-1]


Influences covered by the safety factor Ks

• Differences in equipment assembly

• Dispersion in product quality

• Quality of installation• Aging of the installation during expected lifetime

• Other unknown influences



Determination of the required withstand voltages Urw

• The required withstand voltages are determined by converting the coordination withstand voltages to appropriate standard test conditions.

• Usually different from the coordination withstand voltages.• Derived from the coordination withstand voltages Ucw by the safety factor Ks and/or the

altitude correction factor Ka.

[IEC 60071-1]




Selection of the rated and of the standard insulat ion level(set of standard rated withstand voltages Uw)

• Most economical set of standard withstand voltages Uw of the insulation to prove that all the required withstand voltages are met.

• For each range (I or II) a combination of only two withstand voltages defined:Range I: standard lightning impulse withstand voltage

standard short-duration power-frequency withstand voltageRange II: standard switching impulse withstand voltage

standard lightning impulse withstand voltage• For range I, only phase-to-earth standard withstand voltages are defined, which have to

cover phase-to-earth, phase-to-phase and longitudinal insulation.




[IEC 60071-1]


Definitions




Examples for…

... non-self-restoring insulation(power transformers,instrument transformers*))

*) mixed insulation

... self-restoringinsulation(disconnectors,insulators)



[IEC 60071-1]


List of standard short-duration power-frequency withstand voltages (r.m.s. values in kV)

630570510480

460395360325275

2301851409570

5038282010

1800

750

95

1950

850

125

1675

650

75

2100

950

145

24002250155014251300

11751050550450325

250170604020

List of standard impulse withstand voltages (peak values in kV)



The standard voltage values areall the same for• phase-to-earth-,• phase-to-phase-,• longitudinalinsulation!

Range I :Um = 1 kV up to and including Um = 245 kV


[IEC 60071-1]



Range II :Um above 245 kV

Different standard voltage values for• phase-to-earth-,• phase-to-phase-,• longitudinalinsulation!


[IEC 60071-1]




Outcome of insulation coordination– For three types of insulation

» phase to ground» phase to phase» longitudinal

– and for 4 values each of required withstand voltages Urw

» required continuous operating voltage» required short-duration power-frequency withstand v oltage» required switching impulse withstand voltage» required lightning impulse withstand voltage

�� Standardization of tests for equipment– Reduction of these 12 values to a necessary minimum number of

withstand voltages Uw of the insulation

– Determination of necessary withstand voltages from tables for two ranges of highest voltage for equipment

twelvevoltages



[IEC 60071-1]

Procedure for Insulation Coordination in Four Steps - Summary

Flow chart acc. to IEC 60071-1(Figure 1)

continued next slide



[IEC 60071-1]

Procedure for Insulation Coordination in Four Steps - Summary

Flow chart acc. to IEC 60071-1(Figure 1) (continued)

iso_v_05

Documents

suitable discharge

summaryflow

safety factor

oxide surge

dielectric

cigre technical

required withstand

assumed conventional