Significance:

Part 2 – Development of Standards – Reality checks

Part 6 – Tutorial reviews

A progress report on the development of the Trilogy, presented in a forum organized by the lightning protection

community, to promote harmonization of standards.

It is ironic that in early-2000, when this paper was written, the working group expectation was that by mid summer

a satisfactory consensus would be reached. Alas! The reality is that it took two recirculations to achieve such a

consensus, to the point that publication of the Trilogy could not be accomplished before early 2003, almost three

years after this paper was written.

Filename: Trilogy update
* e 

18-22 September 2000 

THE TRILOGY UPDATE OF IEEE Std C62.41 

Abstract: Progress report on the restructuring of two 

IEEE standards concerned with surges in low-voltage 

a.c. power circuits into a Trilogy of three documents. 

First a basic Guide describes the surge environment, 

then a Recommended Practice proposes a limited set of 

representative surge waveforms for test purposes, and 

finally a Recommended Practice shows how to perform 

safe, repeatable and reliable surge tests on equipment 

connected to these a.c. power circuits. 

Key Words: lightning, surges, standards 

1, INTRODUCTION 

Since 1980 when the seminal IEEE Std 587 Guide on 

Surge Voltages in Low-Voltage AC Power Circuzts was 

first approved, the document has gone through several 

revisions, while a companion, IEEE Std C62.45 Guide on 

Surge Testing for Equipment Connected to Low-Voltage 

AC Power Circuits was developed to provide guidance on 

test procedures. Experience in applying the documents, 

and the availability of new information on the subject led 

to a decision of performing a major update of the two 

documents, mostly the C62.41. The purpose of this paper 

is to present a progress report on the project and invite the 

International Conference on Lightning Protection (ICLP) 

community in sharing common interests about the 

occurrence of surges in low-voltage a.c. power circuits. 

2. HISTORY 

In 1991, the 1980 version cf th,e IEEE 587 G~ide 

(wKch had bee:: :e::mm! !EEE!AIr\!S! C62.41 soon after 

its original issue) was upgraded to a Recommended 

Practice, with the addition of new recordings to the data 

base, and the definition of "Additional Test Waves" to the 

seminal 100 kHz Ring Wave and Combination Wave 

(1,2150 - 8/20 p). 

Since 199 1, the Recommended Practice remain

unchanged, but new information for the data base, and t

perception of a need to describe the scenario of a dir

flash to the building - not included in the scope of t

1980-1991 versions - have created a situation where 

mere update of the document would be insufficient. 

Consequently, the IEEE Surge Protective Devi

Committee and the Standards Board of the IEEE ha

approved a new project, now known as "The Trilog

whereby the two documents, C62.41 [I] and C62.45 [

will be replaced by three separate, but related (a

published simultaneously) IEEE standards. The pres

C62.41-1991 will be split in two, C62.4l.l and C62.41

while C62.45 will remain separate but better connected 

the two C62.41 documents. 

3. THE TRILOGY 

The identification of the three documents will be: 

C62.41.1-2000 - IEEE Guide on the Su

Environment in Low-Voltage AC Power Circuits 

C62.41.2-2000 - IEEE Recommended Practice 

Characterization of Surges in Low-Voltage AC Pow

Circuits 

C62.45-2000 - IEEE Recommended Practice 

Surge Testing for Equipment Connected to Lo

Voltage AC Power Circuits 

To place these three documents of the Trilogy 

perspective, note that the IEEE generically refers to th

types of documents as "standards": 

Guides, in which information is presented with no attem

to steer the reader in a unique direction; 

Recommended Practices, in which several possible choi

are presented, and one is recommended as the first cho

Standards, in which a single approach is specified, with 

deviation allowed. 

* Electricity Division, Electronics and Electrical Engineering Laboratory, Technology Administration, U.S. Department of Commerce 

Contributions from the National Institute of Standards and Technology are not subject to U.S. Copyright. 
The last document of the Trilogy, C62.45 will not 

have major changes. It wiii be an update to make it 

consistent with the recommendations of C62.41.2, with the 

addition of some practical tips on how to perform more 

reliable surge measurements. In contrast, the first 

document of the 1990s vintage, C62.41, is undergoing 

major restructuring. The purpose and the contents of these 

three standards are summarized in the three following 

Sections 4,5, and 6. 

4. GUIDE ON THE SURGE ENVIRONMENT 

4.1 Data base 

The initial approach to a description of the surge 

environment was limited to compiling the results of surge 

measurements made in the field, either by systematic 

monitoring, or on the occasion of staged tests, generally in 

connection with equipment failure investigations. As the 

development progressed, it was recognized that additional 

information on the surge environment can be gained by 

incorporating other data. In its new structure as a Guide 

four elements will be included into the data base: 

1. Recordings of surge events in the field; 

2. Numerical simulations and laboratory research; 

3. Inferences on the surge environment drawn from 

analysis of equipment field failures; 

4. Discussion of the data base. 

The 1980 and 1991 versions of C62.41 proposed th

concept of "Location Categories" as follows, in an effort t

guide designers and users of equipment toward a realist

perception of the surge threat depending on the gener

location within a building, but not precise distances. 

4.2 Location Categories 

The concept of Location Categories was based on th

fact that the inherent inductance of the building wirin

would reduce the current stress imposed by an impingin

surge as distance from the service entrance increases, whi

the voltage stress would not be affected. The concept wa

illustrated in graphic form, showing buildings wher

increasing distance from the service entrance were marke

by fi ne-!in? derr?zrcrr,atinns between the mtegeries. O

course, electrons flowing in the wiring were blissfull

unaware of these demarcations, a fact that was troublesom

to some readers of the document. A possible misinte

pretation of these fine-line demarcations might hav

implications on the rating specifications of surge-protectiv

devices (SPDs) to be installed at a specific location. 

To avoid this too-narrow interpretation the update

Guide will emphasize that "boundaries" separating th

categories should rather be seen as "transitions" connectin

the categories that overlap. The graphic illustration of th

three Location Categories A, B, and C will show, rathe

than the fine lines of 1991, the amended concept an

representation with transition overlaps, as seen in Figure 

Figure 1 - The concept of Location Categories connected by transition overlaps 

888 ICLPZOOO 
However, the concept of Location Categories was and 

remains implicitly applicable only for surges impinging 

upon the building from the outside or generated within. 

These were considered to be the vast majority of surge 

events, and the more rare event of a direct flash to the 

building was considered a special case, which was not 

addressed in the document. The updated version will now 

include that situation, as described in Section 5. 

Given the increasing interest, and some of the 

undocumented perceptions on what is involved in the 

scenario of a direct flash to a building, the Trilogy is 

attempting to provide information presented in a manner 

that will be useful and realistic. To emphasize the major 

difference between common surge events and a less 

frequent direct flash, the surge environment description of 

C62.41.1 is presented in two separate scenarios: 

Scenario I: All surges impinging from the outside or 

generated within the building, except for Scenario I1 

Scenario 11: Surges resulting exclusively from the 

dispersion of the lightning current in the earthing 

electrodes 

The concept of presenting the two scenarios has been 

well accepted among the members of the IEEE SurgeProtective Devices Committee. One of the pitfalls in 

applying this scenario might be an oversimplification made 

in a well-intentioned attempt to simplify the complexity of 

the dispersion of the lightning current among the available 

paths to multiple earthing electrodes. Figure 2 shows an 

a!reac!y very shp!ified building wiring with extJ=,".eous 

metal which still suggests multiple paths for the dispersion 

So far, few if any measurements have been reported 

in the literature to document the details of the dispersion of 

lightning current within a building [3]; [4]. However, 

several numerical simulation studies have been conducted 

[5]; [6]; [7], all involving a certain degree of simplification 

181. This evolving situation is closely monitored by the 

IEEE working group where the Trilogy is being developed, 

to provide the latest consensus at the time of balloting, but 

realizing that this consensus is an ever-evolving goal. 

4.4 From data base to representative waveforms 

In turn, the environment description of the C62.4 1.1 

Guide will sem; as the basis for the definition of the 

waveforms given in the 262.412 Recommended Practice, 

z i:esi;i"lkb in ihe next s~iio~i. Tie waveforms that were 

pr9pcsed iE &+e 1991 version .*i!! be r,&i&iieS iii ;$e 

descriptinr? of Scemrin I, h~? ?he def zition of zippropriate 

parameters for Scenario II is still unresolved as of the 

writing of this paper. Consensus might be reached among 

interested parties by the time of oral presentation of this 

paper at the ICLP Rhodos, where the most recent results of 

this process can be reported. 

5.1 Purpose, proposals, and pitfalls 

The explicit purpose of this Recommended Practice 

to propose a limited set of test waveforms that can be us

for subjecting equipment to representative surge stresses 

encountered in the low-voltage a.c. power environment

This set is aproposal, not a specification; it should 

seen as a menu from which equipment manufacturers a

users can select stress levels, as determined by the select

test wavefom(s) and arnplitude(s) best suited for their ow

application. 

The commonpitfall, however. has been in the past th

the purpose was misinterpreted and the proposals we

turned into equipment specifications that were expected 

be appropriate for all applications. Continuing efforts 

the redaction of the successive versions of the docume

have been made, and appear to have reduced but still n

yet completely eradicated such misinterpretations. 

The menu aspect of this Recommended Practice w

be emphasized by suggesting two types of test waveform

First, a set of two 'Standard Waveforms" recommended f

general applications; then a set of "Additional Waveform

recommended for special applications where they appe

appropriate. 

5.2 Standard Waveforms 

The original 1980 version proposed two representati

waveforms, and these have not changed since. The fi

I- wavelorm, iabeied "0,5 ps - iw kHz Ring Wave" w

constructed on the basis of the then novel recognition th

the traditional test waveforms used in high-volta

laboratories might not be a good representation of t

environment in low-voltage a.c. power circuits. Even t

limited field recordings available at that time were showi

oscillatory, high-frequency waveforms rather than t

textbook unidirectional impulses. 

The second waveform, actually a combination of tw

stress types, was proposed for subjecting equipment to 

voltage stress (1,U50 p) when the equipment wou

present a high impedance, or a current stress (8120 p

when the equipment would present a low impedance. Th

choice was influenced by the wish of not denying the lo

experience gained with those waveforms. In contrast to t

then prevaient test methods where the current and volta

iiiipuises were two separate tesis, this second waveior

would be applied by a generator having the inhere

capability of delivering a voltage or a current stre

according to the impedance of the equipment under te

This new type of generator and waveform became know

as "combination Wave." 
Intended air terminal of 'Lightning Protection System." 

Unintended. but likely air terminal (Ventilation, air conditioning ...) 

Unintended, but possible air terminal if no others available. 

Side flash from down-conductor in the absence of bonding. 

Facility bonding bar. 

Earthing bonding. 

Made earth electrode for building. 

Lightning earthing electrode. 

Heating, ventilation, air conditioning equipment. 

SPDs installed in the service entrance equipment. 

Power utility incoming connection. 

Other utilities (communications, water. ..) 

Total lightning current. 

Portion of lightning current into facility wiring. 

Portion oi iigntning current into iightnlng earthing electrode. 

Ponion ot lightning current into building made electrode. 

Portion of lightning current exit via electric power utility. 

Portion of lightning current exit via other utilities. 

Figure 2 - Example of possible multiple paths for dispersion of the lightning current 
During the process of updating the 1980 vintage of the 

C62.41 Guide into the 1991 version, several waveforms 

were considered by the working group. The final proposal 

was to recommend considering a fast transient, adopted 

from the IEC 801-4 (now IEC 61000-4-4, called EFT for 

"Electrical Fast Transient"), a 10/1000 p Long Wave, and 

a 5 kHz Ring Wave. These waveforms were designated as 

"Additional Waveforms" to emphasize that a test program 

should not be overburdened by unnecessary tests when 

there was no compelling reason to include one or more of 

these additional waveforms in the test regimen. 

In the updating process for the Trilogy, the EFT and 

the Long Wave have been kept as Additional Waveforms. 

In the 1991 version, the 5 kHz waveform was intended to 

emulate capacitor switching surges. In the laboratory, a 

conventional type of energy-storage surge generator could 

produce that waveform superimposed to the powerfrequency voltage. However, it has been abandoned as 

more data became available on the occurrence of capacitor 

switching surges, indicating that lower frequencies, below 

1 kHz, were more typical. Instead, the recommendation is 

offered that specific studies be performed for installations 

where large capacitor banks are being switched frequently. 

6. RECOMMENDED PRACTICE ON TESTING 

One of the outcomes of the Recommended Practice on 

Surge Characterization is a set of tables indicating what 

types of surge test waveforms are recommended for 

specific combinations of conductors at the power port of 

equipment to be tested (phase, neutral, ground). To 

illustrate the process, Table 1 presents a summary of these 

recommendations for surge testing the a.c. power ports of 

equipment (including surge protective devices, of course). 

NOW iiii-iiiiig to the recoiiiiiiendau.iions on aciuaiiy 

.\nrfnrm;..r. th- ranr\mmn..rl-rl tentn :.. A,. inon- --A A,

Y~I IUIIIUII~ UA~ ILA,UIIUIIUIULU ~3~3, 111 LIIG L 7owa allu LII

early 1990s, guidance on surge testing was offered in the 

format of an IEEE Guide. In the Trilogy, with the 

experience accumulated in the use of the C62.45 Guide

augmented by some anecdotal examples of observed 

questionable surge testing procedures, the decision was 

made to elevate the C62.45 Guide to the more compelling 

visibility and status of a Recommended Practice. 

This enhanced version also will address issues raised 

by the shift from analog to digital instruments and the 

resulting effects of aliasing, insufficient resolution, and 

transducer saturation. Precautions for avoiding artifact

will also be included in the recommendations. 

7, SCHEDULE AND RET,ATInNS 

WITH OTHER STANDARDS 

Efforts are being made to effect liaisons with the IEC 

Technical Committees TC37 and TC81, as well as with 

other parties involved in lightning studies. The effort has 

been difficult because the liaisons were not optimized and 

the work was sometimes conducted by different group

without sharing relevant information. It is one of the aims 

of this paper to lower these barriers by presenting the 

subject within the community of the ICLP participants. 

The IEEE working group is hoping that the Trilogy 

will have matured through the summer of 2000, in 

particular the consensus on how to turn the agreed-upon 

Scenario I1 into one set of recommended test waveforms 

that represent the environment. 

At the present time, IEC Publication 61643-1 [9] has 

been released, but it only specifies the types of tests

without reference to the location and environment in which 

the SPDs are to be installed. 

Table 1 

Summary of recommended types of surge tests 

I Scenario I I Scenario I1 

(Surges impinging upon the structure from outside, and generated within) (Direct lightning flash) 

I I I I I I I 

Location 

Category 

Refer to 5.2 for details on the standard waveforms. 

Refer to 5.3 for details on the additional waveforms. 

bn a case-by-case basis. 

Pending development of consensus. 

A I Standard I None I Additional I Additional I Additional I Use the I Case 

100 kHz 

Ring Wave * 

i3 I Standard I 

Combination 

Wave * 

C I None I Standard I None I Additional 1 Additional I 1 

Standard 

EFT Burst 

5/50 ns 

Addiiionai 

1011 000 ps 

Long Wave 

Aaaiiionai 

Capacitor 

Switching ' 

' 

Aaaitionai Category B 1 by 

Ring Wave 1 case 

Coupling 

Resistive 

Coupling 5 
The update of the two original documentsIEEF st d 

C62.41 and IEEE Std C62.45, into a Trilogy will bnng the 

following improvements to these two previous documents, 

notwithstanding the fact that they served well in the period 

of 1980 to 1999 (IEEE has filled over a thousand requests 

for C62.41 since its first publication): 

The new structure will provide readers with a more 

direct route to fulfill their particular needs: 

1. A basic guide providing comprehensive data base and 

the rationale for the simplification leading to the 

recommended standard and additional test waveforms; 

2. A relatively terse description of the recommended test 

waveforms, uncluttered by the data base; 

3. A straightforward and well-connected Recommended 

Practice on surge testing methods. 

The most significant changes in the Trilogy, compared 

to the earlier versions of C62.41-1991 and C62.45-1992, 

are the following: 

Separation of the data base that was appended to 

C62.41 in the earlier versions, when enhancing 

acceptance and credibility of the proposals were 

deemed important elements. A Guide provides a 

comprehensive data base, a Recommended Practice 

provides the standard and additional test waveforms. 

Introduction of a Scenario I1 for the special case of a 

rl&re~! lightning flab t~ the b~i!&ng. Scrh a ~~enkfi~ 

implies higher stress levels for those surge-protective 

devices installed at the service entrance, compared 

with the stress levels suggested for usual applications. 

Introduction of the concept of transition overlaps that 

act as interfaces between Location Categories, rather 

than the boundaries that previously separated these 

categories; 

Removal of the earlier attempt to provide across-theboard waveforms for the case of capacitor switching, 

but instead make recommendation to perform case-bycase studies. 

The development of the IEEE C62 Trilogy update ha

been made possible only with the technical contribution

and moral support of my colleagues, too numerous to lis

them all, from several standards-writing groups, but wh

nevertheless deserve recognition for their voluntary work

Another beneficial factor that needs recognition is th

growing trend toward harmonization among standard

writing organizations, in spite of their initial divergen

positions. 

10. REFERENCES 

[I ] IEEE S:b C62.41- 199: - Reeomiiieii&d pmeiice on 

Surge Voltages in Low-Voltage AC Power Ci~uitz. 

[2] IEEE Std C62.45-1992 - Guide on Surge Testing for 

Equipment Connected to Low-Voltage AC Power Circuits

[3] Moms, M.E., Fisher, R.J., Schnetzer, G.H., Merewether, 

K.O., and Jorgenson, R.E., "Rocket-Triggered Lightning 

Studies for the Protection of Critical Assets," IEEE 

Transactions IA-30, MaylJune 1993. 

[4] EPRI "Investigation of lightning entry into a secondary 

service using rocket triggered lightning", EPRI Report TR

110418, April 1998. 

[S] Birkl, J., Hasse, P., and Zahlmann, P., "Investigation of 

the interaction of lightning currents with low-voltage 

installations and their related threat parameters", 

Proceedings, 2Yd International Conference on Lightning 

Protection, Firenze, 1996. 

I61 Mansoor; A. and Martzloff, F.D. ; "Driving high surge 

currents into long cables: More begets less", IEEE 

Transactions PWRD-12, No.3, July 1997. 

[7] IEC 62066: 2000: General basic information regarding 

surge overvoltages and surge protection in low-voltage 

ax. power circuits. 

[8] Mansoor, A. and Martzloff, F.D., "On the Dispersion of 

Lightning Current after amirect Flash to a Building," 

Submitted for ICLP 2000, September 2000. 

[9] IEC 61 643- 1 : 1998 Surge protective devices connected to 

low-voltage power distribution systems - Part 1: 

Per$ormance requirements and testing methods.