Overvoltage Protection and Insulation Coordination in Power Systems

Overvoltage Protection 

and 

Insulation Coordination 

in Power Systems 

© Siemens 

Fachgebiet 

Hochspannungstechnik 

Overvoltage Protection and Insulation Coordination / Chapter 1 - 1 - 

Prof. Dr.-Ing. Volker Hinrichsen 

Dipl.-Ing. Simona Feier-Iova 

Technische Universität Darmstadt 

High Voltage Laboratories

What is Insulation Coordination? 

Definition in IEC 60071-1 

Definition in IEEE 1313.1 

Fachgebiet 


Overvoltage Protection and Insulation Coordination / Chapter 1 - 2 -

Fundamentals of Insulation Coordination 

Magnitude of (over-)voltage / p.u. 

5 

4 

3 

2 

1 

0 

Fachgebiet 


Voltages limited by arresters 

Lightning overvoltages 

(Microseconds) 

Possible voltages without arresters 

Switching overvoltages 

(Milliseconds) 

Time duration of (over-)voltage 

Withstand voltage of equipment 

Temporary overvoltages 

(Seconds) 

Highest voltage of equipment 

(Continuously) 


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. 

Fachgebiet 



Literature (1) 

[BAL-04-1] G. Balzer 

Power Systems, Part 2 

Chapter 4: Insulation coordination 

Script TU Darmstadt, 2004 

[BAL-04-2] G. Balzer 

Elektrische Energieversorgung, Teil 2 

Kapitel 4: Isolationskoordination 

Skript der TU Darmstadt, 2004 

[CIG-73] CIGRE W.G. 13-02 

Switching overvoltages in EHV and UHV systems with special reference 

to closing and reclosing transmission lines 

ELECTRA 30 (1973) pp. 70-122 

[CIG-79-1] CIGRE WG 33.02 

Phase-to-phase Insulation Co-ordination: 

Part 1: Switching overvoltages in three-phase systems 

ELECTRA 64 (1979) pp. 138-158 

[CIG-79-2] CIGRE WG 33.03 

Phase-to-phase Insulation Co-ordination 

Part 2: Switching impulse strength of phase-to-phase external insulation 

ELECTRA 64 1979, pp. 158-181 

Fachgebiet 




[CIG-79-3] CIGRE WG 33.06 


Part 3: Design and testing of phase-to-phase insulation 

ELECTRA 64 1979, pp. 182-210 

[CIG-79-4] CIGRE TF 33-03.03 


Part 4: The influence of non-standard conditions on the switching impulse strength 

of phase-to-phase insulation 

ELECTRA 64 1979, pp. 211-230 

[CIG-91] CIGRE WG 33.01 

Guide to procedures for estimating the lightning performance of 

transmission lines, CIGRE technical brochure No. 63, 1991 

buch_020.pdf 

[CIG-92] CIGRE WG 33-07 

Guidelines for the evaluation of the dielectric strength of external 

insulation, CIGRE technical brochure No. 72, 1992 

buch_019.pdf 

[DOR-81] H. Dorsch 

Überspannungen und Isolationsbemessung bei Drehstrom-Hochspannungsanlagen 

Siemens AG, Erlangen, 1981 (ISBN 3-8009-1325-9) 

Fachgebiet 




[ERI-88] A.J. Eriksson, K.-H. Weck 

Simplified procedures for determining representative substation impinging lightning 

overvoltages, CIGRE report 33-16, 1988 

[ETG-93] ETG-Fachbericht 49 

ETG-Tage '93: Isolationskoordination in Hoch- und Mittelspannungsanlagen 

vde-Verlag GmbH Berlin, Offenbach (ISBN 0341-3934) 

[FGH-78] FGH Technischer Bericht 1-240 

Isolationskoordination auf der Grundlage der neuen DIN/VDE-Bestimmung 0111 

FGH, Mannheim, Juli 1978 

[HIL-99] A. R. Hileman 

Insulation Coordination for Power Systems 

Marcel Dekker, Inc., New York, Basel, 1999 

[HIN-00] V. Hinrichsen 

Metalloxidableiter: Grundlagen 

Siemens AG Berlin, 1. Auflage 2000 

AbleiterBuch.pdf 


Metalloxidableiter: Grundlagen 

Siemens AG Berlin, Edition 1, 2001 

ArresterBook.pdf 

Fachgebiet 





Latest Designs and Service Experience with Station-Class Polymer Housed Surge Arresters 

World Conference on Insulators, Arresters & Bushings 

Marbella (Málaga), Spain, November 16-19, 2003, Proceedings pp. 85-96 

pub_048.pdf 

[KIN-05] V. Hinrichsen 

Latest Testing Requirements and Emerging Standards for Transmission Line Arresters 

World Conference on Insulators, Arresters & Bushings 

Hong Kong, November 27-30, 2005 

inmr_2005_paper.pdf 

[KIS-84] I. Kishizima, K. Matsumoto, Y. Watanabe, New facilities for phase switching impulse 

tests and some test results, IEEE PAS TO3 No. 6, June 1984 pp. 1211-1216. 

[KOE-93-1] D. König, Y. N. Rao 

Teilentladungen in Betriebsmitteln der Energietechnik 

vde-Verlag, Berlin, Offenburg, 1993, ISBN 3-8007-1764-6 

[KOE-93-2] D. König, Y. N. Rao 

Partial discharges in Power Apparatus 

vde-Verlag, Berlin, Offenburg, 1993, ISBN 3-8007-1760-3 

Fachgebiet 




[PAR-68] L. Paris, R. Cortina 

Switching and lightning impulse discharge characteristics of large air gaps and long insulation 

strings, IEEE Trans on PAS, vol 87, No. 4, April 1968, p. 947-957 

[RUD-99-1] R. Rudolph, B. Richter 

Dimensioning, 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. Richter 

Bemessung, Prüfung und Einsatz von Metalloxid-Ableitern in Mittelspannungsnetzen 

ABB Schweiz AG, Wettingen (CH), 3. Auflage 1999 

Anwendungsrichtlinien_Mittelspannung.pdf 

[THI-01] L. Thione 

Insulation coordination in electrical power systems – theory and application 

Tutorial, ALPI, Milan, 2001 (www.alpiass.com) 

buch_018.pdf 

Fachgebiet 




[WEC-07] K.-H. Weck 

Standardization of insulation withstand levels for UHV systems in 

IEC TC 28 „Insulation co-ordination” 

IEC/CIGRE UHV Symposium Beijing 18-21 July 2007, report 5-4 

5-4_KHWeck.pdf 

Fachgebiet 


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

CATALOGUE_PUBLICATIONS_2005.pdf 


Standards (1) 

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, 2006-07 

Surge arresters – Part 4: Metal-oxide surge arresters without gaps for a.c. systems 

IEC 60099-5, Ed. 1.1, 2000-03 

Surge arresters – Part 5: Selection and application recommendations 

DIN EN 60071-1, 1996-07 

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

60071-1:1995 

DIN EN 60071-2, 1997-09 

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

IEEE 1313.1-1996 

IEEE Standard for Insulation Coordination—Definitions, Principles, and Rules 

Fachgebiet 



Standards (2) 

IEEE 1313.2-1999 

IEEE Guide for the Application of Insulation Coordination 

IEEE C62.11-2005 

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

IEEE C62.22-1997 

IEEE Guide for the Application of Metal-Oxide Surge Arresters for Alternating-Current Systems 

Fachgebiet 



Organization 

1 

2 

3 

4 

5 

6 

7 

8 

9 

10 

11 

12 

13 

18.10.2007 

25.10.2007 

01.11.2007 

08.11.2007 

15.11.2007 

22.11.2007 

29.11.2007 

06.12.2007 

13.12.2007 

20.12.2007 

27.12.2007 

03.01.2008 

10.01.2008 

17.01.2008 

24.01.2008 

31.01.2008 

Fachgebiet 


Lecture 1 

Lecture 2 

Lecture 3 

cancelled 

Lecture 4 

Lecture 5 

Lecture 6 

Lecture 7 

Lecture 8 

Lecture 9 

Christmas holidays 

Christmas holidays 

Lecture 10 

Lecture 11 

Lecture 12 

Lecture 13 

Introduction 

Voltage stresses 

in power systems 

Traveling waves 

Overvoltage protection incl. protective distance 

Dielectric strength (incl. gap factors, 

pollution, rain, parallel insulation, aging) 

Insulation coordination 

Insulation coordination 

Calculation Examples 

Test procedures; condition monitoring (life time aspects, partial 

discharges, non-conventional approaches) 


Organization 

Examination 

Exclusively oral 

Exercises 

None; but calculation examples in the lecture 

Script 

Slides will be available for download 

www.hst.tu-darmstadt.de 

User: studentiso 

PW: isows0708 

Fachgebiet 



Insulation Coordination - Principles 

System 

Equipment 

Fachgebiet 


Overvoltage 

protection devices 

Environment 

System voltages 

Dielectric 

strength 


stress 

versus 

strength


• Voltages of the system 

– Nominal voltage U n 

» rounded value for characterizing the system 

Fachgebiet 


» 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 U s 

» highest operating voltage between phases under normal conditions 

» 12 kV - 24 kV - 123 kV - 245 kV - 420 kV (IEC 60038) 

• Voltages of equipment 

– Highest voltage for equipment U m 

» highest voltage between phases for which the insulation 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 

Fachgebiet 


» system configuration (grid size, degree of meshing, etc.) 

» origin of overvoltage (failure, switching, lightning 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 in 

the system 

Variety of amplitudes and 

shapes of overvoltages 

Variety of operating 

conditions and age 

Variety of 

environmental conditions 

Fachgebiet 


Equipment in 

the laboratory 

Standardized amplitudes 

and shapes of test voltages 

Standardized setups 

and conditions 

Standardized 

environmental conditions 



bb 1 

bb 2 

Fachgebiet 


3 

busbar disconnectors 

2 

line 

1 

Insulation phase - ground 

stressed by voltages between one phase and ground 

1 

Insulation phase - phase 

stressed by voltages between two phases 

2 

Longitudinal insulation 

stressed by voltages between same phases of 

two different systems 

3 


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

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Procedure for 

insulation 

coordination 

= 10 pages! 


...39 pages in sum


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...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. 

Fachgebiet 


Range I Range II 


Procedure for Insulation Coordination - General 

Basic difference between ranges I and II 

withstand voltage 

Fachgebiet 


Range II 

Range I 

[FGH-78] 

peak 

time duration of stress 

gap spacing 3 m 

gap spacing 0.5 m 


Minimum of withstand 

voltage for switching 

overvoltage 

Withstand voltage 

continuously 

decreasing with time 

duration of stress

Procedure for Insulation Coordination in Four Steps 

Fachgebiet 


Determination of the representative overvoltages U rp 

• 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]


Fachgebiet 


Determination of the coordination withstand voltages U cw 

• 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 U rp by the coordination factor K c. 


Typical for 

Germany: 

0.1% per year 

� 1 failure in 

1000 years 

[IEC 60071-1]


Fachgebiet 


Deterministic approach Statistical approach 

Assumed maximum 

of representative overvoltage 

Multiplication by coordination 

factor based on 

operating experience 

Statistical distribution of 

representative overvoltages 

Determination of 

failure probability of insulation 

Calculation of failure risk 

depending on assumed 

coordination withstand voltage 

Coordination withstand voltage 

Assumed conventional U cw (0% cw (0% value) Statistical U cw (10% cw (10% value) 



Fachgebiet 


Determination of the required withstand voltages U rw 

• 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 U cw by the safety factor K s and the 

atmospheric correction factor K t or the altitude correction factor K a. 


[IEC 60071-1]


Fachgebiet 


Influences covered by the safety factor K s 

• Differences in equipment assembly 

• Dispersion in product quality 

• Quality of installation 

• Aging of the installation during expected lifetime 

• Other unknown influences 


[IEC 60071-1]


Fachgebiet 


Determination of the required withstand voltages U rw 

• 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 U cw by the safety factor K s and/or the 

altitude correction factor K a. 


[IEC 60071-1]


Fachgebiet 


Selection of the rated and of the standard insulation level 

(set of standard rated withstand voltages U w) 

• Most economical set of standard withstand voltages U w 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 voltage 

Range 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. 



Definitions 

Fachgebiet 



[IEC 60071-1]


Examples for… 

... non-self-restoring insulation 

(power transformers, 

instrument transformers *) ) 

*) mixed insulation 

Fachgebiet 


... self-restoring 

insulation 

(disconnectors, 

insulators) 



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

10 

70 

275 

480 

20 

95 

325 

510 

Fachgebiet 


28 

140 

360 

570 

38 

185 

395 

630 

50 

230 

460 

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

20 

325 

1300 

40 

450 

1425 

60 

550 

1550 

75 

650 

1675 

95 

750 

1800 

125 

850 

1950 

145 

950 

2100 

170 

1050 

2250 

250 

1175 

2400 


[IEC 60071-1]


Fachgebiet 


Range I: 

U m = 1 kV up to and including U m = 245 kV 

The standard voltage values are 

all the same for 

• phase-to-earth-, 

• phase-to-phase-, 

• longitudinal 

insulation! 


[IEC 60071-1]


Fachgebiet 


Range II: 

U m above 245 kV 

Different standard voltage values for 

• phase-to-earth-, 

• phase-to-phase-, 

• longitudinal 

insulation! 


[IEC 60071-1]


Outcome of insulation coordination 

– For three types of insulation 

Fachgebiet 


» phase to ground 

» phase to phase 

» longitudinal 

– and for 4 values each of required withstand voltages U rw 

» required continuous operating voltage 

» required short-duration power-frequency withstand voltage 

» 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 U w of the insulation 

– Determination of necessary withstand voltages from tables for two 

ranges of highest voltage for equipment 


twelve 

voltages

Procedure for Insulation Coordination in Four Steps - Summary 

Fachgebiet 


continued next slide 


Flow chart acc. to IEC 60071-1 

(Figure 1) 

[IEC 60071-1]

Procedure for Insulation Coordination in Four Steps - Summary 

Fachgebiet 



Flow chart acc. to IEC 60071-1 

(Figure 1) (continued) 

[IEC 60071-1]

Overvoltage Protection and Insulation Coordination in Power Systems

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