ML100330820

Memorandum and Order (Scheduling Initial Prehearing Conference)

ML100330820
Person / Time
Site:	Bellefonte
Issue date:	02/02/2010
From:	Bollwerk G Atomic Safety and Licensing Board Panel
To:
SECY RAS
References
50-438-CP, 50-439-CP, ASLBP 10-896-01-CP-BD01, RAS 17105
Download: ML100330820 (5)

Text

United States Nuclear Regulatory Commission Official Hearing Exhibit Entergy Nuclear Operations, Inc.

In the Matter of:

(Indian Point Nuclear Generating Units 2 and 3) v....v-.P< REG(J~" ASLBP #: 07-858-03-LR-BD01

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Docket #: 05000247 l 05000286

< 0 Exhibit #: ENT000246-00-BD01 Identified: 10/15/2012

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i; Admitted: 10/15/2012 Withdrawn: ENT000246

~1-" +O~ Rejected: Stricken: 12/10/2012 Submitted: March 29, 2012

... ** .... Other:

Condition Assessment of Belted PILC Cables After 7 To 68 Years of Service Vitaliy Yaroslavskiy, Member, IEEE, Carlos Katz, Lifo Fellow, IEl!.7i~ and Matthew Olearczyk, Member, IEEE TABLE [

CABLES EV ALUAlED Abstract - This paper summarizes results of laboratory evaJuation of eight service aged PILC belted cables, produced by different fR8ted ,'oItage, No, of Condo Length, manufacturers in the period between 1937 and 1998. Cable No. Vintllge Manufacturer kV (and. size m performance was evaluated from different perspectives, including No. 110 partial discharge pattern, ionization factor at room temperature, I 1937 Okonite Cable Co. 7 4 70 AWG dissipation factor at elevated temperatures, up to 90 *C, dielectric 2 1940 Habirshaw Cable 7 3 350 61 strength of tbe cable insulation, analysis of tbe laminated insulation & Wire Corp. kcmil structure, moisture content, etc. Overall results indicate that, unless John A. Roebling' s 350 3 1957 7 3 76 Sons Corp. kcmil cable insulation is affected by moisture intrusion, most of the cable John A. Roehling's 350 characteristics still meet requirements for new cables. The only 4 1957 6 3 87 Sons Corp. h .-mil exception is dissipation factor at elevated temperature, which Phelps Dodge No. 110 5 1971 6 3 52 suggests that cable ampacity is reduced by cable aging. Cable & Wire Co. AWG General Cable 350 6 1972 6 3 150 Corp, kcmil 350 7 1992 TIle Okonite Co. 7 3 48 kcmil J"dex Terms - PILe cables, field aged, partial discharge, dielectric 500 losses, ioni;,otion factor, dielectric strengt.h, ampacity. 8 1998 The Okonite Co. 6 3 90 k:cmil I. lNTRoDucnoN P aper in!>ulated lead covered (Pll..,C) cables have long been a backbone component of uman medium voltage distribution systems. Several leading North American utilities, in collaboration II. D ESCRIPTION OF SAMPLES A brief description of the cables evaluated is provided in Table 1.

Manufacturers and vintages are based on imprints found on with the Electric Power Research Institute (EPRJ), recently marker tapes.

removed a number of PILC cable leogths from their systems.

Cables that had been in service for 7 to 68 years were subjected to The cables have construction design variables including; number a series of laboratory tests to evaluate their conditions and analyze and size of conductors, insulation thickness, possible differences the aggregate of the overall results. The testing was conducted at in oil and papers used, thickness of the lead sheath. All test Cable Technology Laboratories (Cn) . Guidance and direction cables were of the belted design. The oldest cables were were provided by Consolidated Edison Company of New York and unjacketed; more recent cables, starting from 1957, had a jacket Pacific GdS and Electric Company of Califomia. covering the lead sheath. Individual cable sample cross-sections are shown in Figure 1 In total, 8 cables were evaluated. They had been removed from a 4 kV distribution system due to replacement of the cable system.

Individual reports, issued on each cable, are available at EPRl This paper does not list all test results; it rather concentrates on typical perfonnance and most significant findings.

The main objectives of the project were:

- to collect data on performance of service aged cables;

- to assess the condition of particular cables;

- to analyze cable characteristics in relation to their use in cable diagnostic testing;

- to elaborate test approaches fur use in assessing similar cables.

Manuscript received ,20 10 ; revised ,2010. Paper no.

lPWRD* *2010 This work was supported by the E lectric Power Research Institute.

V . Yaroslavskiy and C. Katz are with Cable Technology Laboratories, New Brunswid.. NJ 08<X)3 USA Fig. I . Cross section of M. OI~lJcz.,.k is with Electric Power Research Institute, Palo Alto, CA 94 J04 t:ahk:s Il::itOO.

USA

Each sample was submitted to CTL in one continuous length.

These were straight cable lengths, with no accessories installed.

Due to the fact that the condition of cables may vary along their length, tests were performed on three sections of the same cable, each approximately 15 m long. The three sections were taken from the ends and the middle of the available cable lengths (Table I), so that the distance between the test specimens varied from 0 to 52 m.

IlL TEST PROORAM The test approach was based on earlier experience gathered by CTL personnel in testing paper insulated cables [1-7] . The following tests were performed on each specimen:

a) Inspection for general overall condition and presence of mechanical damage.

b) Partial discharge at ambient temperature.

c) Power factor vs. voltage (ionization factor).

d) Dielectric power loss and dissipation factor at ambient temperature, 70 and 90°C.

e) Impulse test at cable conductor emergency temperature.

t) Six hours high voltage withstand test at 8 kV/mm (200 V/mil), followed by a similar test for up to 7 hours8.101852e-5 days <br />0.00194 hours <br />1.157407e-5 weeks <br />2.6635e-6 months <br /> at 16 kV/mm (400 V/mil), both executed at ambient Fig. 2. Test set up.

temperature.

g) Dissection, paying special attention to the distribution of The length of the cable between terminations was about 13 .5 m.

butt spaces, registrations, presence of wrinkles, ridges, Passing current through the lead sheath provided uniform tom tapes, wax, deficiency of oil, etc (if present). temperature distribution throughout the cable cross-section. A h) Hot oil tests performed during dissection for the presence general view of the set up is provided in the upper picture III of moisture in the paper insulation. Figure 2.

i) Folding endurance of paper tapes on cable adjacent to the breakdowns to establish if insulating tapes had thennally To minimize the possibility that oil, being used in the temlinations, degraded . would mix with the cable impregnating oi~ the sample ends were shaped into an open S (lower picture in Figure 2) In this Tests b), c) and d) were performed between each individual phase arrangement the termination oil could not enter the main part of and the other two (or three) phases connected to the lead sheath, the cable. On the other hand, elevated sections of the test as well as between all three (four) phases connected together and specimen, undergoing evaluation at high temperatures, had oil the lead sheath. Test e) was performed between each individual moved to lower locations, so that a local deficit of oil developed .

phase and the other phases connected to the lead sheath. Test t) Therefore, times to breakdown obtained within the project were was performed with all phases connected together, against the somewhat conservative (rather than being too optimistic).

lead sheath.

V TEST RESUl.TS Test procedures were based on AEIC CS 1-1968 [8]. Although cables were manufactured at different times, the 1968 issue was To ease comparison of overall performance of the cables tested, most . /'

used for testing all samples, to provide a common base for their of the results are summarized~ ~;n)k'e~, in Table V Y comparison. In additio~ to account for different insulation thicknesses, the cables were tested in accordance with their Vi.mal Examinatioll

{-oltage ratings, as shown in Table I , this in spite of the fact that Cables were thoroughly examined during their removal from the they all were used in a 4 kV distribution system. reels, as well as during preparation of the end terminations and during dissection of laboratory and field breakdowns. Three of the cables (No . I, which was the oldest one and did not have a rv. TEST SET UP jacket, Nos. 5 and 7) were in good shape, with no peculiarities to The specimens were set-up for electrical evaluations by removing be mentioned . Cable 4 had an opening, at approximately 15.5 m the lead sheath from the cable ends. On each end, the oil from one of the section ends, all the way through one of the impregnated paper belt was removed and tapered, while the conductors, probably made to ground the cable during removal.

individual phases were separated and terminated in an oil-filled The affected section, about 20 m long, was discarded; the test cylindrical enclosure. The enclosures were adjusted, at their sections did not appear to be affected by this opening.

lower end, to the cable diameter with the help of rubber reducers.

Since one of the main factors limiting PILC cable life is lead corrosion, special attention was paid to the condition of the lead 2

However, this finding was of interest to justifY that the cable sections had been removed from locations adjacent to joints and therefore to visualize as to from where moisture also could have entered the cables (both samples 3 and 4 were affected by moisture intrusion).

Partial Discharge Tests were started by gradually increasing voltage, until partial discharge (PD) inception took place, holding at this voltage for about 30 seconds, followed by a gradual decrease in voltage, until PD extinction. The entire voltage exposure cycle did not exceed 3 minutes. The test sensitivity was better than 5 pC for single phase testing, and between 8 and 10 pC for all phases connected together.

PILC cables are characterized by unstable parameters of PD, changing significantly over time. Therefore, the tests were repeated several times (at least 3) on each individual cable phase and also with the three (or four) phases connected together. A few minutes were allowed between successive applications of Fig. 3. Lead corrosion: voltage for dissipation of space charges accumulated in the cable a - cable 6; calciwn carbonate on insulation during the preceding test.

surtilCe oflead under polyethylene jacket All PILC cables tested had a complicated performance: PD b - cable 3; advanced corrosion of lead sheath under bulged started at low intensities (I0-20 pC), converting abruptly to and ruptured jacket strong discharges (hundreds to thousands pico coulombs) with c - cable 2; erosion in lead further voltage rise. It appears that small voids in butt spaces of sheath caused by corrosion the cable insulation evolve into large empty spaces (possibly due to displacement of oil by elevated gas pressure developed by initial discharges) conducive to a significant increase in the sheaths. Figure 3 provides examples of diffurent degrees of corrosion, discharge intensity.

from mild (cable 6, relatively young in the population examined, with a polyethylene jacket) to well pronounced (cable 3, of 1957 vintage, Partial discharge between a few hundred and maybe even a few having rubber jacket and covered overaIl with insulating tapes) The thousand pico coulombs, applied during a limited test duration, is inside of the sheath of these cables was clean and shiny.

of no consequence to the PILC insulation. This type of insulation can support PD for a long time. In other words, PD testing at the The worst condition was that of cable 2, the only sample that beginning of a test sequence is not expected to affect subsequent incorporated a field failure. Figure 3c shows severely corroded results.

(pitted) spots in the lead sheath, found in cable sections adjacent to either side of the failure.

With exception of the two oldest cables (Nos. I and 2), all other cables had extinction voltage above the operating stress of the Corrosion of metals can be divided into two major types: uniform system from which they had been removed (2.3 kV phase-to-and localized. Uniform corrosion involves oxidation of metal in ground), so that they essentially had operated in a PD-free the presence of a small amount of water (for example, moist air).

environment (Table V). Test results for the worst performer (in In this case corrosion products cover the metal with a uniform relation to PD activity) are shown in Table n. In each case the layer of usually hydrogenated metal oxide, which protects the lowest reading for several voltage TABLE II metal underneath from further corrosion. The other type is applications is reported. PDCHARAClERISTICVOLTAGES characterized by discreet pitting. It occurs when the metal is CABLE 2 immersed in water and corrosion never stops. All cases shown in A substantial difference between Figure 3 represent the second type, at different stages of individual sections of the same Phase corrosion progress.

cable needs to be noted. In .

addition, despite the fact that A 7.1 6.7 Other findings were related to discolored paper insulating tapes at individual phases of belted B >10 -

the ends of sample Nos. 3 and 4. Interestingly, in sample 3 the C &.1 6.6 cables are in intimate contact to belt and outermost tapes in the phase insulation were discolored, A+B+C 75 6.2 each other, their characteristics while in sample 4 the innermost tapes were affected the most, and SectIOn 2 differed significantly.

the discoloration diminished towards the outside. Despite this A 2.2 2.1 difference, the origin of the discoloration appears to be the same: Power Factor v.s. Voltage B 6.5 5.&

C 7.0 6.2 tar-like compounds used to fill joint casings. These compounds aonization Factor) A+B+C 4.0 2.8 permeate over time into the paper insulation, either through the The tests were performed in Sec1:!on 3 conductor interstices (staining the inner tapes), or under the lead accordance with Section ]0.1.3 A 8.3 5.0 sheath (causing discoloration of the outer tapes). In neither case of the AEIC CS 1-68 at average B 8.4 5.5 did this phenomenon affect the performance of the cable system. voltage stresses ranging from 20 C 8,5 6.0 A+B+C 8.5 5.0 3

to 100 V/mil (0.8 to 4.0 kVlmm). Power factor was measured 3.5..------------------------,

---"';':- SeCtion 1:Ptiase A-between each individual phase and the other phases connected to

• Section I.~B the lead sheath, as well as between all phases connected together 3 _

" Sedron I . pt1ase C Section I. all ph/lses and the lead sheath. Ionization fuctor was calculated as a " SedIoo 2. pt1ase A difierence between the maximum and minimum values of the 2.5 o S6CIioo 2, phase B I>. Section 2. phase C power factor in the indicated voltage range. -x-Section 2. All phases oE

• Section 3. phase A Table III summarizes the maximum power factors, measured at g 2

• SedlOn 3. ~ B

.. Section 3 phase C room temperature and nominal operating voltage stress of ~ " _Section 3. 811 phases 1.6 kVlmm on different phases and sections of the same cable, as to L5+---------------------~--~----------4 Q.

well as the maximum differences between sections and phases within the same cable (the difference between phases might be helpful in distinguishing bad performers during on-site diagnostic Section I testing). Figure 4 provides a visual presentation of the data for 05+-_____ 6 ______6__~~~---~~~-~---~

cable 4 that had the highest ionization factor.

O+-------r------,----~---_r-----~

A wide spread of results should be noted, with some cables well o within industry specification requirements for new cables, the Voltage Stre!'iS. kVImm others exhibiting relatively poor condition. It is interesting to 15 gphA.';e A note that the power factor values were not as indicative of a poor I!lPhaS8 B cable condition, as was the level of ionization factor.

2.5 +'=='=""='='.. ---.~,----.---,-.-----------!

Significant variation in the performance of different sections of the same cable needs to be noted. As with other properties j 2+----*----*-*----*------~--**-*----~=----:

=

tested, this indicates a pronounced non-consistency of the cable performance along the feeder length. It is commonly 1

.E 1 5 recognized that PILC cables, as manufactured, are pretty uniform, so that the non-uniformity apparently has developed during cable service. It is also of interest that the difference between cable phases was not that pronounced; however, it was o

-'1 _2 -..~

still noticeable, and in most cases (where moisture was not Fig. 4. Power factor at room temperature (upper pictme) and ionization factor involved) there was a good correlation between PD parameters (lower picture) in cable 4 (worst performer of all cables).

and ionization factors of individual cable sections and phases.

cable was evenly heated through its length and cross-section by Further, it needs to be noted that, in relation to old cables, the circulating current through the lead sheath. Each section was term "ionization factor" does not necessarily mean that there is held at constant temperature for at least one hour after the a lack of oil, which could create a void that is subject to required temperature was achieved at the cable outside.

discharge activity in the insulation structure. It could mean, for example, that the high values of this characteristic could be due Variation of cable capacitance versus temperature was very to high levels of moisture and/or the formation of wax. minimal (even in bad performing cables) and not worth of discussion. In contrast, dielectric loss at high temperatures Capacitance and Power Factor vs. Temperature provided significant information on the cable condition. A Tests were performed at the cable rated voltage (as listed in summary of the results is provided in Table V. The table Table 1) and at three temperatures: ambient, 70 and 90°C. The incorporates the maximum value of power factor measured at each TABLE III temperature on all cable sections and phases (including the POWER FACIDRATRCDMTEMPERA1URE AND OPERATING VOLTAGE configuration with all phases connected in parallel). An AND I0NI7ATION FAClDR AT S1RES.<;ES UP TO 4 KVIMM example of temperature dependence of power factor (for the worst performing cable 3) is shown in Figure 5. Extreme data Power Factor at 1.6 kVhnm, ole Ionization for each section of this cable is provided (the worst and best Variation Variation Factor, No. Vintage between section~ between pbases Mu 0/. performing phases of each sections of this cable).

I 1937 0.34 0.03 0.41 0.09 2 1940 0.35 0.01 0.42 0.10 As with previously described characteristics, there was also a great 3 1957 0.22 0.13 0.67 0.89 variation of dielectric loss at high temperatures between different 4 1957 0.15 0.29 0.64 3.10 sections of the same cable. Subsequent evaluations revealed that in 5 1971 0.26 0.02 0.30 0.03 two of the cables (Nos. 3 and 4) there had been moisture ingress in 6 1972 Ol7 0.03 0.41 089 7 1992 0.20 0.02 023 0.05 the end sections, which was one of the reasons for inconsistency of 8 1998 0.22 0.03 027 016 cable performance. In particular, cable 3 (Figure 5) had section 3 AEIC CS 1-68 requirements for new cables <0.6 <0.3* affected by moisture, while the other two sections tested appeared to

• In accordance WIth AEIC CS 1-68 there are no reqUIrements for belted cables. be in a significantly healthier condition Still, these two last sections The requirement for new shielded cables is 0.3%, maximum had pretty high power mctor at elevated temperature.

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VI. CONCLUSIONS [6] "Development of a Method to Introduce Controlled Amounts of Moisture into Paper-InsUlated Lead-Covered Cables", EPR! Report 1014868, May The condition of eight PILe cables, rated 6 to 7 kV, removed 2007 '

from a 4 k V distribution system after 7 to almost 70 years of [7] "Evaluation of Line Resonance Analysis (LIRA) lor Diagnosing Defecis in PILC Cables", EPR! Report 1019595, September 2009.

service, was evaluated by laboratory testing. Cables were mainly

[8J "Solid Type Impregnated Pape~ Insulated Lead-Covered Cable removed due to system replacement; only one of them contained Specifications ", AEIC Specification CS 1-68, 10th Edition, April 1%8.

a field failure. A series of test methods, including measurement [9] "Power Cable Ampacities", IPCEA Publication No. P-48-426, 1967.

of partial discharge, power factor at different voltage and [lO} William H. Press, Saul A. Teukolsky, William T. Vetterling, Brian P Flannery "Numerical Recipes in C: The Art of Scientific Computing",

temperature levels, dielectric strength under impulse and ac Cambridge University Press, 1992.

stresses, structural analysis, etc., were employed. f II] "Guide For Field Testing Of Shielded Pawer Cable Systems Using Very Low Frequency (VLF) ", IEEE Std. 400.2, 2(XJ4 Most of the cable sections tested, including the oldest ones, [I2l "Effect of Controlled Amounts of Moisture on the Performance of Paper-Insulated Lead -Covered Cables", EPR! Report, Jamtary 2010.

appeared to be in good condition, indicating that cables with similar characteristics can provide further long and reliable X. BIOGRAPHIES service. Out of eight cables tested, only one should probably have been considered for immediate replacement. Even the Vitally Yaroslavskiy was born in Russia on September 21, 1950. Received an MS degree in Thermo-Physics from failed cable, after removal of a short section containing the Moscow Power Engineering University in 1973.

failure, was still in a reasonably good condition. Until 2000 he w(ned foc the Russian Research Instilllte fur Metrological Services, Moscow, de\cloping metOOds and meastIfl"nlmI standan::i'i to. fRCise high voltage measurements.

Among mechanisms of cable degradation, noted on older cables, He has been associated with Cable Technology Labooltories were lead corrosion (in one case conducive to moisture penetration since 2001 as a Senior Test lc-:ngineer and VP Technology, with and cable failure), elevated moisture content (likely, due to a expertise in testing and performance evaluation of medium and number of reasons), local deficit of oil, formation of wax; both high voltage cables and accessories. Mr. Yaroslavskiy is the moisture and wax are conducive to elevated dielectric losses in the author of over 60 teclmical papers.

insulation. Signs of different degradation mechanisms could Carlos Katt (M'70-SM78-F'87) was born in West Germany sometimes be recognized in the same cable length. on August 18, 1934. He ra:eived an Ekxtrical Engineering degree from Polyteclmic fustitute of Quito, Ecuador in 1961 and an MS degree from Stevens fustitute of Teclmology, Hoboken, Results of laboratory tests confirmed the worthiness of field New Jersey in 1970.

diagnostic testing. However, a large number of variables, From 1962 to 1971 he was associated with General Cable governing PILC cable condition, may not allow for designing a COIp. Research Center and from 1971 to 1974 with the set of criteria, which can warrant a clear differentiation between laboratories of Phelps Dodge Wire & Cable. In 1974 he became Assistant Director of R&D at General Cable Corp.,

"bad" and "good" cables. A complex testing approach may need and later Teclmical Director Power and Control cables for to be adopted, if a comprehensive assessment of the cable General Cable InternationaL He has been with Cable Technology Labomtories as condition is sought. Chief Research Engineer since its founding in 1978. Mr. Katz's special field of activity is the investigation of extruded and laminar dielectric high voltage power cables, the manufacture and properties of such cables and the extension of service A loss of ampacity (up to 17 %) was noted on aged PILC cables. life of installed cables.

This loss was due to elevated dielectric losses in the cable Mr. Katz is the author of more than 40 teclmical papers and holds 16 U.S.

insulation at the maximum operating and emergency patents related to high voltage cables. He is a voting member of the ICC, a temperatures. Considering typically low or moderate loading of member of CIGRE and of JICABLE. He is recipient of the ICC Dr. George Bahder Memorial Award and of the IEEE 20 I 0 Herman Halpering A ward.

Utility feeders, this factor might not be critical; however, it must be recognized and considered for cable operation. Matthew OIearczyk was born in the United States on November 14, 1%1. He received an Engineering degree from Widener University in Cl1e;ter Permsylvania. He worked at VII. ACKNOWLEDGEMENT Public Service Electric and Gas Company of New Jersey and The authors are indebted to several of their associates who have is now employed by the Electric Power Research Institute (EPRf).

contributed to the laboratory investigation. Mr. Olearczyk is Senior Program Manager at EPRl he directs EPR!' s applied research portfolio for the electric VIII. REFERENCES distribution systems research area, which includes technology development/assessment and demonstration as

[11 C. Katz "Evaluation of Old Vintage Solid-Type Impregnated-Paper- well as analytical studies to identity industry leading pmctices, environmental Insulated Lead Covered Cables', Minutes of the 82nd Meeting of the impacts, customer behavior, and applications of smart grid infrastructure. He is Insulated Conductors Committee, Columbus, Ohio, April 17-20, 1988. responsible for the continuing development of the distribution systems research

[2J C Katz and M. Walker "Further Serviceability of 40 Year Old PILC Cable: program and business development across the EPR! worldwide regions.

Millules of the 90th }"feeling of tile IllSulated Conductors Committee, Mr. Olearczyk is the author of numerous papers and EPR! reports. He is an ViclOria, British Columbia, April 26-29, 1992. active member of the IEEE PES and the AEIC CEC.

[3J G.W. Seman, C. Katz, S.V. Pancholi "Evaluation of 230 kV HPFF Pipe-Type Cable with Wrinkled and Creased Insulating Tapes", IEEE Transactions on Power Delivery, Vol. PWRD-lO, No.1, pp. 25-33, January 1995.

[4J C Katz "Condition Assessment of PILC Cables", Minutes of the //3th IIL,ulated Conductors Committee, Cincinnati, Ohio, April 27-30, 2003.

[5J C Katz "PILC Cable - Related Failures Analyz-ro at cn. 19%-2005",

,l{inutes of the 121st lnvulaied ConduclfJrs Committee, Orlando, Florida, May 2007.

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