ML20147F822

Comments on Draft Reg Guide 1.XX, Lightning Protec for Nuc Pwr Plants Dtd 780825(RS-705-4).Feels Draft Does Not Reflect Previous Comments.Forwards Proposed Reg Position & Comparison of Proposed Position W/Position in Draft Guide

ML20147F822
Person / Time
Issue date:	11/20/1978
From:	Rosa F Office of Nuclear Reactor Regulation
To:	Morrison W NRC OFFICE OF STANDARDS DEVELOPMENT
References
RTR-REGGD-01.XXX, RTR-REGGD-1.XXX NUDOCS 7812260022
Download: ML20147F822 (16)

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o U'U TED S TATES NUCLEAR REGULATORY COi"':SSION f .t;s,:::je

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' l MEMORANDUM FOR: W. M. Morrison, Assistant Director for General Engineering Standards, Division of Engineering '

Standards, OSD I FROM: Faust Rosa, Chief, Power Systems Branch, DSS THRU: V. Benaroya, Acting Assistant Director -

for Plant Systems, DSS \/

SUBJECT:

REGULATORY GUIDE 1.XX, " LIGHTNING PROTECTION FOR NUCLEAR POWER PLANTS DATED 8/25/78 (RS-705-4)

References:

1. Memorandum from E. G. Case to Robert B. Minogue dated August 8, 1977, Concurrence in OSD Task Initiation Form for Task No. RS 705-4, Development of Regulatory Guide on Lightning Protection. -

2. Memorandum from Faust Rosa to R. J. Mattson dated April 5,1978, ACRS Subcommittee Meeting 4/5/78 on the Preposed Regulatory Guide on Lightning Protection.

3. Memorandum from c aust Rosa to R. J. Mattson dated April 27, 1978, Status of PSB Review and Conmnts on Draft Reg Guide 1.XX,

" Lightning Protection for Nuclear Power Plants", dated 3/9/78.

4. Memorandum from Faust Rosa to R. J. Mattson dated May 17, 1978, Draft Reg Guide 1.XX, " Lightning Protection for Nuclear Power Plants", dated 3/9/78, and its Value/Impa t Assessment (SD Task RS 705-4). ..

5. Memorandum from W. M. Morrison to R. L. Tedesco dated August 11, 1978, Summary of Meeting with 050 on LigFtning Protection -

August 1, 1978.

I have reviewed the subject draf t guide as requested by your memorandum to me dated August 25, 1978, and bz.ve the following comments:

The subject draft does not reflect most of the major comments which I have made on prior drafts of this guide (references 1 through 5).

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' W.: M. Morrison jgq, ',

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.Rather than reiterate my prior comments, I have written a complete t Regulatory Position (Enclosuref1) which embodies.those prior comments, and which I believe will better provide the necessary lightning pro-tection for nuclear' power plants with greater cost' effectiveness to the industry.. This' proposed position is also consistent with the thrust of the H. R. Denton memorandum to the Commission on lightning .i protection dated August 16, 1978. Enclosure 2 is a comparison of my_

proposed position with the position of the subject draft guide.

I recorc.end adoption of this proposed position. I_also reccmmend that.the' discussion section of the guide and the value impact. statement be revised-to accurately reflect the proposed position including the ,

basic philosophy and engineering principles embodied therein. ,

Should this recommendation not be accepted, I request that my proposed position be included as an alternate position in the value/ impact.~

assessment when the guide and value/ impact assessment are issued for R

public ccaments. -The information in enclosure 2 is intended to aid yourf staff in writing a value impact comparison of the alternati.e. .

approaches. ' My management has informed me that this course of ' action i is consistent with the new procedures' for public comment en. draft prior to consideration by the Regulatory Requirements Review Ceramittee. . r Also, please note that my. proposed position C.2 fulfills the commit- 1 ment (unresolved item 2 of Reference 4) I;made during 'our meeting' on l August 1, 1978. J

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.j r -o t 3 F. 7 Faust Rosa, Chief  ;

Power Systems Branch  ;

Division of Systems Safety l cc: w/ enclosure ,

H. Denton . R.'Tedesco 1 R. B. Minogue D. Eisenhut '

G. Lainas

([~~G.-Quitsch E._G._. Case [j]}@i7 . R. Satterfield j

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3. Ranauer C. Miller  :

R. Mattson' D. Tondi V. Stello M. Srinivasan G.-Arlotto S. Rhow.

-E.'Marinos PSB Members n

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Enclosure 1 Proposed Regulatory Position for RG 1.XX " Lightning Protection for Nuclear Power Plants" F. Rosa - 9/20/78 C. Regulatory Position Conformance with the principles and requirements of the following standards (as applicable) provide acceptable methods for complying with General Derign Criteria 2 and 18 of Appendix A and with Appendix 8 to 10 CFR Part 50 with respect to the design, qualifica-tion, construction, installation and. testing of systems and components-providing protection against lightning for light-water-cooled nuclear  ;

power plants, subject to the following:

NFPA (National Fire Protection Association) No. 78-1975; Lightning Protection Code, Part II - Protection of Build-ings and Miscellaneous Prcperty, and Pac c III - Protection ,

of Structures Containing Flammable Liquids and Gasses; ,

ANSI C62.1-1975, American National Standard - Surge Arresters for Alternating - Current Power Circuits; and ANSI C62.2-1969, American National Standard Guide for Application of Valve-Type Lightning Arresters for Alternat- l l

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1. Protection of Structures Lightning protection should be provided against direct strokes to sfructures and exposed equipment installations including containment, auxiliary buildings, off-gas stacks, fuel-tanks, meteorological towers and other components important.for maintaining the safety'of the plant. The systems and equip-ment that provide this protection shall conform with the  !

78-1975, subject to principles and requirements of NFPA No.

the-following: . Sections 2101(d), 2102(c) through (i). and 2122(b) shall be replaced by the.following: Aluminum sha?

not be used as a conductor or structural support member.

2. Protection of Switchyard Equipment Against Direct Strokes _

4 Overhead ground wire shielding, augmented by air terminals ~

1 and masts as necessary, should be p'rovided.to protect all switchyard components of the power system (including overhead j line power circuits from the switchyard to other plant structures)againstdirectlightningstrokes. The complete shielding system' including the overhead components, inter-connecting conductors and grounding system should be designed and installed in accordance with established conservative design principles and practices of the electric utility industry; .and the ground resistance should not exceed one obra.

1 In addition, the~ design should provide a shielding effectiveness such that shielding failure stroke current the current in a lightning strike which bypasses (I g, the shielding and strikes a live component directly) will i not exceed id,000 amperes as defined by the relation

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where the' maximum strike distance (rs m) is a function of shield-wire height (h), live component height (y), and shield- angle (gs )*

All dimensions are in meters, I max "E -

3. Protection of Transmission Lines Against Direct Strokes Overhead ground wire shielding snould be provided to protect all transmission lines terminating in the switchyard against direct lightning strokes. This shielding system'should be provided over the entire length of the line, however, it should definetly.be.-

provided for a minimum distance of one-half mile from the' switch-yard terminus of the lines. The complete shielding system includ-

-ing overhead ground wire, tower components, interconnecting con-ductors, and tower grounding system should be designed and installed in accordance with established conservative. design The principles and practices of. the electric utility industry.

overhead ground wires should be carried into the switchyard and tied to the switchyard ground' system. In addition, for each i transmission line for a minimum of one-half inile from the' switch-

-yard,.the design should provide a shielding effectiveness such that shielding failure stroke Surrent (I,x) will not exceed l

. 15,000 amperes, as defined in Position C.2 above.

. ., ,t Details for determination of shielding effectiveness using this method are. contained in a paper by G. W.: Brown, Lightning Performance - I  ;

Shielding Failures Simplified, IEEE Transactions on Power Apparatus e and Systems, Vol. PAS-97, No.1, January / February .1978. Note: This' paper specifically addresses transmission line shielding but the methodology is readily applicable to switchyard' shielding. ,

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4. Surge Protection for Switchyard Terminal Ecuipment Station type surge (lightning) arresters should.be installed on both the high and low voltage sides of all unit, and start-up or .

station service transformers in accordance with the following provisions:

a. The arresters should conform to all the applicable require-ments of ANSI C62.1-1975 including design, construction-ind qualification testing with the following exception: In -

Section 7.5.1, High Current Short-Duration Test, the test <

surge current wave-shape should be at least 8 x 20,gsec (instead or the less conservative options also permitted by the standard).

b. - The arresters should be provided with a discharge counter and a leakage grading current meter to facilitate surveillance and.

assessment of the functional capability of the installed i arrester.

c. The arresters should be selected and applied in accordance with conservative application of the principles and fethodologi f i

contained in ANSI C62.2-1969, includina the following: . .

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(1) Insulation coordination should be performed at a  :

discharge current of 20,000 amperes minimum.- (See

. Sections 3.2.1 and 3.2.2 of ANSI C62.2).  !

(2) The protective ratio (margin) for impulse coordinai-tion should be 1.2 minimum; for_ switching surge -

coordination'it should be 1.15 minimum. (SeeSec-  ;

i tion 3.5.1 of ANSI C62.2).  !

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5. Surge' Protection for Class 1E Switchgear j Station type surge arresters should be provided for all Class lE switchgear components that are conn,ected to expo' sed overhead -

lines either directly or through a short length of cable.

These arresters should conform to the following: ,

a. The arresters should be selected and applied in con- i formance with Positions C.4.a. C.4.b and C.4.c above.

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b. The arresters should be installed in the circuit up-stream of the feeder breaker; and the physical arrange-i ment-should be such as to preclude damage to the switch- ,

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6. Periodic Surveillance of Lightning Protection Systems Periodic surveillance of' lightning protection systems and com-ponents addressed in Positions C.1 through.C.5 should be. performed, consistent with other planned periodic surveillance programs for outdoor electrical'insta11ations. As a minimum this periodic 1

Esurveillance should include:  ;

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a. Visual inspection, augmented by conductor continuity tests

.and ground resistance measurements as deemed necessary, to ,

ascertain the functional capability of the systems pro-i viding protection against direct strikes to structures, switchyard components and transmission lines.

b.- Visual inspection of the surge arrester installation to determine if there is evidence of physical damage, surface contamination, or.other deterioration in the arrester or its line and ground connections which could result in failure of surge protection. The viscal inspec-tion should be augmented by conductor continuity tests and ground resistance measurements as deemed necessary to as .

certain the functional capability of the surge arrester inttallaticns. i A check of the surge arrester discharge counter reading l

c. -l and leakage grading current reading for each arrester. .

A pennanent record of these data should be mainta~1ned and an assessment of arrester functional capability should be determined by comparison with previous readings and with the reconnendations of the manufacturer in this regard.

If the functional capability of an arrester is deemed to be marginal, it should be replaced in accordance with

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established maintenance procedures for this type of equipment.

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ENCLOSURE 2 Comparison of Proposed Position (Enclosure 1) '

.With Position in RG 1.XX " Lightning  ;

Protection for Nuclear Power Plants" Dated 8/25/78 j

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• The proposed position is based on the following basic considerations:

1. Lightning protection for structures has been a human concern for i

centuries. The design principles and practices 'necessary for pro-viding complete protection for all types of structures have been-

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l well established for some time, and are embodied in NFPA No. 78- l 1975, Lightning Protection Code - Parts II and III. Therefore, a Regulatory Guide endorsing this national standard (plus I&E follow to assure implementation)'will be the most effective and efficient means of assuring that nuclear power plant structures are adequately protected against lightning. l l

2. Lightning protection for electric power systems and components.

a has been a primary concern of the electric utility industry since its inception. The design principles and practices have evolved i

over the years based on empirical data derived from observations and measurements of.the effects of lightning on actual power sys--

tems and components. These principles and practices and ' relevant.

data base are well established and.extensivelyLdocumented in the ec.-- g.p., , . ._., pre._' g. ys- . ,, -,y.. .w.,, og, ym ..g ,-,,*- ..p re. '

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literature and in National Standards. They are routinely implemented by the electric -utility industry in a conservative manner, particularly at generating stations jswitchyards and the bulk transmission network.

Experience -indicates that very effective lightning protection is being provided for all the on site electrical systems; and there is -

no experience even remotely involving lightning induced common mode f failures of redundant safety-related systems or components. The re-I fore, a Regulatory Guide endorsing the applicable national standards (ANSI C62.1-1975, ANSI C62.2-1969), and augmenting these standards as necessary to i'nsure their conservative application and to include surveillance, will be the most effective and efficient means of assuring that the on-site electrical systems (safety and non-safety) of a nuclear plant are adequately protected against lightning.

3. The most direct, effective and least expensive lightning protection for outdoor electrical systems-and components is provided by an overhead grounded shield (ground wire and/or mast) installation.

The effectiveness of existing installations designed in accordance with current engineering practices and standards is confirmed by the fact that the maximum measured discharge current fcr station type surge arresters is 15KA. Therefore, the Regulatory Guide addressing lightning protection should simply include provisions for assuring .

the continued conservative application of current engineering prac-tices to the. design of these overhead grounded shield systems.

These provisions should be quantifiable in terms of shielding effectiveness, i.e., shielding bypass stroke current magnitudes.

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4. In view of item 3 above, a regulatory requirement for peak, withstand current capability in excess of the 65KA specified by ANSI C62.1-1975 for statiot type arresters is unwarranted (R.G.1.XX specifies 200 KA). The impact on the industry of a 200KA requirement would involve either (1) development of new arrester designs with this capability, or (2) using existing arresters with 65KA capability connected in parallel. As'noted  !

in our comments on the prior version of R.G.1.XX, the cost of implement-ing either option is not insignificant. Also, although option 2 appears' f feasible and most capable of early imp)ementation, .it will require ex-tensive full scale operational testing to verify expected performance.

Finally, in our opinion, a requirement (200 KA) so out of line with pre-  :'

sent engineering principles and practices without valid justification could only have a detrimental effect on staff effectiveness and effi-ciency throughout the area of technical review of electric power systems.

5. The onsite electrical distribution system, because of its extensive branching, voltage transformations, and other electrical discontinuities, is inherently '

resistive to propagation of impulse voltages to the low voltage levels (110V) which serve sensitive solid state type of equipmentI That is significant attenuation of voltage impulses is inherent in the design of electric power distribution systems. This is particularly true for the redundant Class IE systems. .Furthennore, electrical equipment at all voltage levels is designed, based on industry experience over many years, with impulse voltage withstand capability commensurate with its design voltage. Sensitive equipment, safety or non-safety related, is specifically designed for noise / pulse withstand capability. This is the most direct, most effective d least expensive method of voltage impulse protection for this type

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of equipment. The most effective way of assuring that this protection, f

. t is provided for this type of equipment is by appropriate environmental- i i

qualification. Provisions for accomplishing- this are already embodied  !

in IEEE Std. 323-1974.

Specific Comments-  ;

-The following is a section summary comparison of the PSB proposed position, C. . Regulatory Position, with respect to the R.G.1.XX Part C." Regulatory Position".

Proposed Introductory Remarks

.The introduction identifies and endorses three national standards that address lightning protection for structuresand AC power systems.

R.G. 1.XX makes no such endorsement.

Proposed C.1.0 - Protection of Structures This section identifies the structurcsat the plant site that should f be protected and endorses NFPA No. 78-1975 with one exception for guidance on implementation. The exception being the prohibition of the use of ,

aluminum as a conductor or support member.

R.G.1.XX (Section C.4.0) references NFPA No. 78-1975 as a footnote.

Proposed C.2.0 - Protection of Switchyard Eouipment Acainst Direct Strikes This section endorses state-of-the-art methodology developed b / G. W. Brown by which the maximum current in a lightning strike which bypasses the shielding can be controlled by design.

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By introducting this methodology and requiring an upper limit for shielding bypass stroke current of 15KA, the 65KA peak withstand current capability now required by national standards for station type arresters provides better than a factor of 4 margin. This obviates the need to consider 200KA as required by R.G.1.XX Sections C.1.0, C.2.5 and C.2.6. The PSB assessment of the impact of the 200KA rat-ing is found in the preceeding general comments.

R.G.1.XX does not directly and specifically address the subject of switchyard protection. This subject is indirectly covered under the R.G.1,XX section on protection of structures. We also note the requirement for a nominal 40* core of protection (R.G. 1.XX Section C 4.3) is less conservative than implementation of the PSB proposed alternative methodology.

PSB C.3.0 - Protection of Transmission Lines Against Direct Strikes This section applies the methodology of C.2.0 above to the transmission lines for a minimum distance of one-half mile from their switchyard terminus.

With the exception of the endorsement of the above methodology, R.G.

1.XX (Section C.3.0) is essentially the same as the PSB alternative.

Proposed C.4.0 - Surge Protection for Switchyard Terminal Eouipment This section endorses in detail ANSI C62.1-1975 and ANSI C62.2-1969, requires arresters to be provided with a discharge counter and a l leakage grading current meter, requires insulation coordination at 20 KA minimum and defines the protective ratios (margin) for impulse and switching surge insulation coordination.

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R.G. l')DC (Sections C.l.0, iC.2.5 and C.2.6) requires a discharge capabili ty

- for station type arrestersoof 200KA as opposed to the referenced standards requirements of 65KA. (See our comments on the 200KA rating in the general comments above). Section C.2.8 endorses the' qualification testing section of ANSI C62.1-1975. Section C.2.9 endorses- the design tests of ANSI C62.1-1975 but require: the substitution of 200 KA for the discharge tests. Section C.2.10 endorses ANSI C62.2-'1969 for insula-tion coordination for transformer but requires that for safety equipment connected to these transformers the voltage due to arrester discharge current of 200 Kf. chould not axceed the. safety equipment withstand capa-bility. This appears to be another way of saying that insulation coordina-tion should be performed at 200KA (as opposed to 20KA specified by ANSI C62.2-1969 as being conservative)thereby contradicting the prior endorsement of the standard.

Proposed C.5.0 - Surge Protection for Class 1E Switchgear This section applies .the same requirements of C.4.0 above to protection of Class 1E switchgear connected to exposed overhead lines either directly or through a short length of cable by requiring arresters to be installed up-stream of the feeder breaker and physically arranged to preclude damage in the event of arrester failure.

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R.G.1.XX(Section C.2.6)has similar. requirement at the 200KA level but does not address physical protection in the event of arrester failure nor does it distinguish requirements based upon whether or not overhead ifnes are part of the feeder circuits. (See the general comments section for further comments on the 200KA rating).

Proposed C.6.0 - Periodic Surveillance of Lightning Protection Systems This section outlines an in-situ periodic surveillance and test program of visual inspection, continuity tests and resistance measurements for assur-ing functional capability of the protection systems. Also, a check of the surge arrester discharge counter reading and leakage grading current reading for each arrester is required. A permanent record of these' data i

will be maintained and'an assessment of arrester functional capability can be determined by comparison with previous readings and with the recomendations of the manufacturer in this regard. If the functional . capability .

of an arrester is deemed. to be marginal, it should be replaced in accordance with established maintenance procedures for this type of equipment. The above forms the basis for not requiring the periodic removal of arresters for laboratory testing.

R.G.1.XX(Section C.2.1) requires removal from serv *ce and full scale testing of representative arresters at five year intervals. R.G. 1.XX does not address _

in-situ visual inspections, measuring of continuity and resistance, or checking of discharge counters and leakage grading current readings at any periodic interval.

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8-Note: -The remaining portions of R.G. 1.XX not discussed above were taken directly from the ANSI' Standards (i.e. sections C.2.1, 2.2, 2.3,. 2.4).

When these sections taken directly from the ANSI Standards are coupled with the references discussed ~in the preceeding parts of this comparison-(i.e. parts C.1.0 and C.4.0 above), we can see no reason why R.G. l.XX does not fully' endorse (with comments)'the national standards itemized in'the introductory remarks of our proposed alternative. -

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