ML23251A029

FOIA-2023-000163 - Responsive Record - Public ADAMS Document Report. Part 11 of 19

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FOIA-2023-000163
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Niagara Mohawk Nine Mi>e point Unit 2 Event of 13 August ]991 Report by: Melvin L. Crensbam Consulting Engineer Po~er Systems Engineeriag Department General Electric Company Schenectady, NY 8 September 1991

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5 iagara Mohawk 5 ine Mile Point Unit 2 E vent of 13 August 1991 05:4S Qn August 13, 1991, at 5:48 Abf the Unit 2 phase B generator step-up transtormer failed. Oscillographic records of the event are available from a digital data recorder at the Scriba Substation. They show various 345 kV and 11 5 k V system voltages and currents. Figure A with notations is attached.

The four cycles preceding the fault show no signs of a gradual degradation or a developing disturbance. The oscillographic traces and station protective relay targets reported, indicate a ground fault occurred on the high voltage winding.

Depression of the 345 kV phase 8 bus voltage to about 39% of the prior value was observed from the oscillographic trace. This suggests the involvement of only a portion of the entire winding. The 345 kV line currents and voltages show rapid development of the ground fault beginning at point 1 with the ground current reaching a constant value of 1,300 amperes in 1 1/2 cycles at point 4, The flashover in the faulted transformer occurs just preceding a maximum in phase 2 to neutral voltage (as would have been expected) at point 2. The 345 kV line current in an unfaulted phase increases in step function manner to 350/o of the prefault value at point 3, No high speed recordings of voltages or currents within the plant were available. No sequence of event recordings were available to correlate relay operation times. Due to the large amount of magnetic energy coupling the generator rotor and stator, and known electrical parameters, thc decay of fault current contributed by the generator to the solidly connected transformer would have spanned a number of seconds as thc field decayed.

Relay operation targets reported were:

l. Transformer Differential Relay (Type BDD) on Transformer 2MTX-XM1B.

2. Transformer Neutral Current Relay (Type IAC).

3. Overall Unit Differential Relays (Type BDD) in phases 2 and 3.

4. Generator Phase Overcurrent Relays (Type PJC) in phases 2 and 3.

r Fv Following isolation of the generator and failed transformer from the power grid, marked 5 on Figure A. only a single 345 kV phase to ground voltage record is available. The magnitude of this voltage on an unfaulted phase is 74fo of the pre-fault value. Since generator neutral current is limited to less than 8 amperes. it is known that the faulted transformer appears as a line to line fault with some impedance to the generator. By trial and error calculation, generator.

line currents are found to be 0, 1.9 and 1.9, multiples of the rated value of 31,140 amperes. The line-to-line voltages have magnitudes 74 lo 74 lo, and 25%

of the rated value of 25,000 volts. The decay of this voltage for 0.2S seconds of the recording has a measured time constant of 2.7 seconds. The calculated value of the impedance of the faulted transformer as seen by the generator is 0.23 per unit.

Conditions prevailing during the six cycle time period following the fault, marked 2 on Figure A, cannot be determined with certainty. The exact nature of the fault within the transformer is not known and the physical evidence will be strongly affected by the continued flow of energy from the generator due to the inherent time constant. The flashover of only a portion of the HV winding is evident since the 345 line voltages to neutral remain at 39%o, 867o and 86'1o of the pre-fault values. The presence of "residual" in the measured 345 kV line currents provides the evidence of transformer neutral to ground current. This requires that the fault involves a path for current to ground from the high voltage winding. Recorded voltages and currents show a step change to new values and no dramatic change during the time period of the record, which totals somewhat less than 1/2 second. It could be said they are "cleaner" and less distorted than commonly seen oscillograph recordings of faults.

Given these observations and since both the generator and the system were supplying fault current into the faulted transformer, generator line-to-line voltages preceding isolation would be expected to be greater than those immediately following isolation.

It has been speculated that very high frequency energy (mHz region) may have causal malfunction of logic and control circuitry in the UPS equipment. A broad-range of frequencies would be expected in any arcing phenomenon such as occurred in this fai1ure. Nothing in the available data or design parameters of the plant equipment would suggest an extraordinary generation or propagation of higher frequency components. 'Ihe failure of a transformer and internal arcing is not a rare occurrence. Comparison of oscillographic charts

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from similar events in other plants show nothing unexpected or unusual in this particular failure. It must be borne in mind that the sampling rate of the recorder is listed as 5.814 kHz and frequency components in excess of perhaps 500 Hz would not be accurately portrayed.

GE experience in testing of typical power transformers (such as the Lnit Auxiliaries Transformers) provides an indication of the expected coupling between windings at radio frequencies in the region of 1 megahertz: The attenuation factors range from 1,000: 1 to 10's of thousands: 1. Direct measurements could be made in this plant to determine attenuation factors for individual transformers over a range of frequencies. These tests would be made on non-energized transformers using an RF signal generator and a sensitive, calibrated detector.

Attached recent articles on electro-magnetic interference. Reference 1 discusses IEC 801,4 and the characteristics of electrically fast transients.

Reference 2 discusses testing of ground connections.

V i The possibility of elevation of thc station grounding system as a result of this disturbance was postulated. The relatively high level of ground fault current, estimated at 1,300 ampercs from the available recording, would not have been conducted into the plant. This current can only fiow in Rom the 345 kV system for the 6 cycle period required for relay and circuit breaker operation to achieve isolation. The generator ground current would have been limited to less than 8 ampcres by the neutral grounding equipmcnt. Elevation or differences in ground potential within the plant would therefore not have been expected during this event.

Reference 1 discusses the problem of achieving a "super" ground and concludes that a stable ground reference for interconnected equipment is of greater significance. Since normally circulating ground currents are not expected, testing with very low voltages and currents is recommended. Note especially the recommendation to test with a frequency non-harmonically related to the power line &equcncy.

The transformers stepping the voltage down to successively lower voltage levels are connected in a manner to minimize coupling of power frequency and higher frequency. components between thc various busses. Specific configurations are:

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l. Normal Station Service Transformer-delta 25 kV to wye 13.8 kV with 400 ampere resistive grounding on the 13.8 kV side.

2. Load Center Transformers-delta 13.8 kV to wye 4.16 kU with 4R ampere resistive grounding on the 4.16 kV side..

3. Load Center Transformers-delta 13.8 kV or 4.16 kV to wye 600 volts with neutral solidly grounded on the 600 volt side.

4. Reserve Station Service Transformers-wye 115 kV, delta 4.16 kV, wye 13.8 kV, The 13.8 kV neutral is 400 ampere resistive grounded. The 4.16 kV circuit is connected to a zig-zag grounding transformer with a resistor in the neutral connection, presumably for 400 amperes.

These configurations provide "effectively grounded" distribution busses as defined in TEE Standard 142 and will serve to limit transient over voltages.

This is in accordance with design practices deemed prudent and conservative within the power industry.

The industry continues to review the effects of geomagnetic disturbances on power transformers.

While no evidence is seen of voltage distortion in the four cycles preceeding the failure, excessive duty could have occurred if these transformers had been subjected to low level direct current previously. References 3 and 4 are attached for perusal.

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fncfustrfal Equfpment EISCtt'OfllCS Ill lndLIStl'Igf APPIiCatienS A Discussion of Fundamentaf ENlC Princfpfes for Electronic Controllers ln an industrial Environment By 4t'iHiam 0. Kimmel. PE Kimmei Gerke Associates, Ltd EDDIC problerrs i~:h:ndustra! ccnuois are bances are a weH known irdustral problem. cally a power disturbance prob'.em.:s: .

aggravated by harsh eni.ronments. mixed In iac:. when a problem occurs. ke tirst the car..er of residual eiiects of o-.

ec.'".noiogies and a laclc of umform E!ifC though': is:o blame the power company. disturbances. Any 'ind;sinai or commer:

guidebnes. T:is arLicie '>el concentrate on Often power quality is a problem (especially suucture has sigiu8cant .'ow ~equen

he common as;ec

s of electronic controls if grounding issues are inciudedl. but the currents circulating:hrough t.".e grou in an !ndustnal en>".ronment. which is problem is almost always generated by system. sometimes because the .nergy generally mucn harsher:ban the ofGce adjacent equipment. intentionally dumped onto the ground (s.

envirOnmenL Tradiuonal problems with power include as with an arc weider) and someur..

What is the industrial enviroment and spikes and transients, sags and surges, and because of unintenuonal coupling or v what can be core about it! The environmen outages. which threaten the eiectroiucs via an inadvertent connection between neu includes the entire gamut of '.he basic the power supply. These problems are and ground somewhere in the!aciiity.

threats. power disturbances. RFI. and fairly weil documented and are often solved Radio Frequency Interference. R ESD. RFI and power disturbances may be using power conditioners or UPS. dio frequency interfer~nce affects bo locally generated or not. Mixed technolo- The most common power problems analog and digital circuits. with ana'c gies compourd:he problem. Digital circuits confronting electronics today is the sag circuits being generally more susceptibl are used to switch."ne voltages via relays. which ~icaily occurs during turn on and Surprising to many, the pnncipie threat Analog sensors are input devices:o digital the spikes which typically occur during turn not the TV or FM stauon down the roai controls. off of heavy inductive loads. ~<..e sags but rather it is the hand held L~snut:~

Increasingly. there is a need for a simply starve the electronics. The high carried around by facilities personnel. A or.

ooperauve effort between the designers. frequency ttansients barrel right through watt radio will result in an electnc ne!d ~

manufacturers and instailers to come up the supposedly Stered power supply to (Ne volts/meter at a one meter distance with a rock-solid system. A common attack the electronics inside. enough to upset many electromcs systems complaint is that the mstallers or mainte- Digital circuits are most vuhierable to IEC 801.3 speciGes immunity to elec ".

narce people won't follow the instaUation spikes which cause data ettors or worse. Gelds of one to ten volts per mete requirements. This may be true, but it Analog circuits are most vukierable to depending on the equipment. with tive must change. smce there are problems continuous RF riding on top of the power. volts per meter being Se level for typic which cannot be solved at the board level. FIPS PUB 94 provides guidelines on equipment. As can be seen from the abov It is also true that manufacturers often eiectrical power for commercial computers. approximation, three volts per meter is nc specify installation .equirements which are This is good infortnation, but beware that an excessive requirement, and even:e not practical to impleinent, and there are factory power is much noisier than commer- volts per meter is fairly modest.

documented cases where the prescribed cial power. Electrostatic Discharges. EiecLc installauon procedures wil! cause rather The guidehces of IEC 801.4 speci5es an static discharge is an intense short durauoi titan cure a probietts. electrically fast uansient (EFT) that simu- pulse, having a riseame of about one The!adt of umiken guidelines has ham- lates arang and other high speed noise. nanosecond. This is equivalent:o a burs.

pered EMC prtiless in the industriat Ebs are quite short ranged they of 300 MHs interference. Static buildup.

arena. Fortunately, the European Commu- diminish rapidly with distance due to induc. of 15 kV are not uncommon.

nity is working to adopt the IEC 801.x tance in the line. But at short range, they Dry climates, including northern climate'.

specilications. and domestic companies are devastatmg.

would be wise to adopt them, even if there Unfortunately, attention is placed on the is no intention to export. front end of the electronics, the power Wham Kimmel is a pn'ncipal with Kimme.

supply. With industrial controls, the prob- Gerome Associates. Ltd. The firm special.

The Basic Threats lem is the controlled elements. If the i@ca in preventing and solving electromag.

The three basic threats to industrial electronics is controlling line power, the netic interference and compaabQity (E.Mh electronics are power disturbances, radio disturbances sneak in the back end where EMC) problems. Mr. Kimmei can frequency interference, and ESD. little or no protection exists. reached at 3544 N Pascal, St. PauL .~i~

Power Disturbances. Power distur- System ground, while not being specifl- 55108, or telephone 612.330-3728.

EMC Test 4 Design

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i suitcl.e I piouer F:g.'re '.. Amp'.'Ger detnodulanon. Figu:e 2. Transient!eedback path.

n ~".nter. offer opportumty !or ESD. en cour ters a noriinearity such as a semicon- to heavy equipment. wtuch.s;itc. -.

Industnai environments. with the:r moving ductor device. All such devices give rise to hy heavy starting .'oads and inducnve .

eq ipment. are loaded with potenual ESD a DC level shift when confronted with RF. a<<wn of TyptcaUY the e!ectronic con:r sources: rubber rogers. belts, and produc- ln a radio receiver they are called detec- switch Une power using relays or;;.-.

uon ou'.put such as plasnc and paper roUs. tors. Noniinearities are minimized in linear This exposes the back end of the cont;=

all add up!o a real ESD th:eat. and t."is devices, but:here is always enough to cause to substantial line transients. which coi-r."meat is more likely to occur even m problems. The upshot is that the ampli6er back to the circuit power and ground

elanvely moist environments. Look

o IEC demodulates the RF. generates an errone- disrupt the digital circuitry as shown 801.2 .'or ESD standards. ous signal. and passes this error on. This Figure 2.

effec'. is shown in Figure 1. Output hnes are It is mandatory that the transient:

Elec! ronics Design similarly affected, with capacitive couphng rents be diverted or blocked. since Electronics:s generally the ultimate back to the input. system cannot withstand t.".e .-.~g'igital victim of:nterference. The hter.'erence The soluuon is to prevent the RF from tudes likely to occur with an inducuve k:i Gnds its way through various paths:o the getting to the amplifier. either by shielding unless special steps are taken.

electronics equipment itself. Let's concen- or filtering. The most common path to the Self jamniing can be Unuted by contrcli trate on w'rat can nappen to your electronics amplifier is via an external signal ine from when you switch !he Une. using ze from !he back door. that is. by direct the sensor. but if the ekctronics is not crossing devices. Of partic~ importan radiation into the electronics and by con- shielded. direct radiation to the circuit board is the mrn off. since dtat is when ducted:nterference through:he signal and may also present a problem. inductive kick occurs.

cont:oi lines. Assuming filtering is the sekcted method. lf a6 power switching used zero crossu Sensors. Low level sensors. such as use a high ~frequency Glter, designed to devices. the transient levels in the facto ther...ocouples. pressure sensors. etc.. are bkick signals up to 1 GHz or even more. wouki be dramaticaily reduced. Unfor.

characterized by very low bandwidtbs and Use femtes and high frequency capacitors, nately, that goal is well off in the futu:

!ow signal levels. A major Meat to these Do not rely on your low frequency Glter to Until then, expect that high voltage pow sensors is radio frequency interference. take out RF. transients wlloccur, and they must be de either from nearby hand held transmitters At the op amp. you shouM also decouple wldl.

or more distance land mobile or Gxed your plus and minus power to ground at tbe Optical couplers and relays do not provi transmitters. chip. If your ground is carzying RF, you can sufficient isolation by themselves. Tht But:hese are high l'requency, much anticipate the same probkm mentioned high capacitance provides an excegent hii above the bandpass of your amph6er. right? above, since it will comtpt the reference frequency path, and if they are stacked t Wrong! Low frequency amplifiers are level. in an array, tbe capacitance wi6 add up plagued by two,ybeaomena: out of band Data Lines. Digital data lines wiU be pass surprisingly low frequencies. The:

response and <<stso rectification. These upset by the RF problem as in anakig, but capocitances an't be elim'mated, but yc combine to provide false information on tbe levels necessary to upset are higher. can design yow control circuits to minimiz levels to the system. Instead. digital data lines are tnucb more couphng paths and to maximize low impe<

All amplifiers have a normal bandpass, susceptible to transient ghtches. All signal ance alternate paths.

typi6ed by a 20 dB/decade roUof or more lines should be 6ltered to pass only the Transient suppressors should be installe at the high end. But resonances due to stray frequencies necessary for operation. If the at tbe kiad, which is the source of the spih inductance and capacitance will give rise to threat lies in the bandpass of tbe signal, but they can be installed at the controUt amplifier response Gve orders of magnitude then shielding or optical links will be as weal.

or more above the nominal bandpass of the needed. An interestmg effect occurs when con amplifier. This means an audio amplifier Switched Power Lines. This refers bining zero crossing SCR regulators wu will respond to signals in the hundreds of specifically to the power being contro9ed low level Mnsors which use line frequerc MHz. by the controller device. Industrial control- noise canceHng techniques. Very seftsitiv The second aspect occurs when RF lers are commonly tasked to control power sensors sometimes are sampled. for t JQIL"August a~!

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'f80 , burro u High Current Pouer VAC DC I PS Electroni>>:s Fir're 3. Common industnai powe. supply. Figure 4. awful:rple ground paths.

enure power yc!e to cancei the ine l(ore or'.eh '.he problem is conducted. eliminate RF of g.ound noise...at freq'ncy conipohent. If t..e samp!e occurs eirher 'aa power or graurd. The problem work, but:hese problems can be rc.

co.","u;.ently wi:h ire power sw'.tching on occurs due:o power and g.ound distur- with an isolat:on rant(armer:o =".-..-

or oif.:he average :o rhe sensor will be bances caused by the equipment. It is an all neutral to ground noise and ~~rh "~II po;

.pse'.. and an e.-.or ~4 "e recorded. too common pracdce to draw controiier linc Glters. So you may wan:;o try power f;om the same source as feeds the inexpensive approach nrst.

System Design and Installation power eqtupmcnt. T."is power may provide Data I.inks. Data links are su.~ng Once >e elect:onics is designed. it :he recessary energy to drive the equip- over the er'.tire!acirty. exposing ther.:

becomes a p.oblem of!he system integratar ment. but it is not suitable to power the two principle e((ects. ground raise are and installer:o ersure that thc electranics electroiucs lFigurc 3). pickup. Ground nois>>; will cause data er.-

is cravided wuh the environment far which Hopefully, all indusuial equipment wiU unless the electronics has been designe" it was des;gned. Most of thc umc. this have electronics powered from a separate accornmodatc potential differences of ->>

work is performed by power experts and low power 120 volt circuit. It solves several eral volts or more. This is accampbs; clectricians. and they are not always aware problems. First. it separates the electron- with dif(crential drivers and receivers:f =.

of:he intcrfererce probkm. Often, on site. ics power from the probably very noisy must be direct coupled. Optical 'hnks-rhe power quality is blamed for thc equip. indusu@ grade power, prevendng the eventually take over these links.

rrent anomalies. But the problem can often switching transients and startup sags from The other aspect is RF pickup. Inexpe be avoided by following a (ew basic prina- genug to the electronics. Second, if it is sive shielded cable is suitable ples. necessary to condition the electronics po~er Ground borh ends! Do not app (ar:.'urpose.

The industrial conuol device is either from an extet".A problem, it is tar cheaper single point ground techniques to RF. i!

integrated into a system at!he factory or to condiuon the watts necdcd (or electronics Iaw frequency ground loop problem:s instaL'ed separately on site. Controllers power than it is to condition thc kilowans threat. then onc end can be capaciuve handle a varicty of devices such as motor required by the system.

speed controls. positioning devices. weld- If power cannot be separated. then it is ers, etc. fnterferencc presented to the necessary to provide a bu!letproaf power Summary electronics can be signiGcandy reduced by supply. preferably incbrding an isolation Industrial electronics are subjected rc appropriate measures outside of the elec- transformer, to separate the entire power harsh environment. Good design and inst.

uonics box. supply from the electrical equipment. !ation techniques will minimiae problems There is no way to accurately assess die Ground Noise. Ground noise, inevita- thc Geld. Adhcrencc to the Europe; rhreat without test data. But rcgardlcss of ble in industrial environments. must be standards, IEC 801.x is a good start, ev>>

the br(oration avai!ab!c. much can be diverted from the electronics modu!c. if you are only markeung in thc USA.

accomplished by correct instagation, and it Multiple grounds in a system wiG often doesn't cost much if done at the start. result in ground curt ents circu!sting through Bibliography RetroGts become cosdy. especially if ac- the cquiprnent. and ground noise circuhting FIPS PUB 94, Guideline on Elec'ac:

companied with factory down time. through thc electronics path will cause Power for ADP Installauons. Scptcmber Let's consider dsc same prob!cms from rnalfuncuon. Figure 4 shows some typical 1983, a system standpat. Your goal is to limit ground loop situations. IEC 801-2. Electromagnetic compatibilit.

the interference wfskh must be handled by A common approach is to demand a super (or industrial. process measurement an<

the electronics. ~arth ground. This is good, but it is not a control equipmcnt, Elcctrostauc dischargr Direct radiation to the electronics is not cure all. and often a super ground cannot requirements, 1984.

often a problem in an industrial environ- be achieved, no matter how you uy. How (EC 801-3. Electromagnetic compatibi!it!

ment, but it does occur, and most often with do you get a super ground from the third (ar industrial. process measurement anI a plasuc enclosure. The NEiMA type 4oor? The real need is to gct'a stable ground control equipment, Radiated electromag enclosures provide enough shielding for reference to all interconnected equipments. cetic Geld requirements, 1984.

most mdusuial needs. If you don't want to If this equipment is closely located, then a IEC 8014, Electromagnetic compatrbilit:

use a metal enclosure, be sure !o get very low impedance interconnect is feasi- (or industrial-process measuremcnt ar.:

elecuonics which will withstand the RF ble. control cquipmcnt. Electrical fast:ransreht which will occur. Power conditioners are o(ten tasked to burst requirements. 1984.

EMC Test 8c De .<n

e industrial Fquipment Equipment Ground Bondlng-Designing for Performance and Life A Discussion of Ground Connection Fundamentals to Control EMl By D.B.L. Durham Dytecna Ltd, UK The problem of achieving satisfactory earth eqtdpment to a stable ground point. achiev. inductance. At very high ~equencies:r bonds or ground connecuons has plagued ing adequate levels of cabk shiekhng and for stray capacitance across the strap EMC engineers for many years, not only many other reasons. Many designers un- donunate. This means that the volt "-:

because the bonds are often vital for the derstand the requirement for short. fat bond across a bond is generaily a funcuon achievement of satisfactory equipment pei- leads to minimiac ground inductance, but inductance and frequency. Based on Ohr.".

formance but because they affect the long few appreciate that a critical aspect is the Law this volt drop is shown in Equador. ~

term performance of equipment after it has connection resistance with which the bond For transients the voltage drop is giver..

been introduced into service. strap is attached to the equipment ground Equation 5.

Recommendations on bonding have ex- point. Thc basic requirement of any bond isted in the form of military speciBcations, Z Rt + cutLS is that it should have as low an impedance such as Mil Std 1310. Mil 188-124A and as possible (uille55 it is a dchbcratc induc-Mil-B.5081 (ASG) for some years and these tive bond to limit ground currents). Tbe V IZ ~ jauU have generally proved satisfactory for most impedance is a combination of the resistive new builds. However. these speci6cations and the inductive components. Thc resis- d1 (5

have certain limitations in that they gener- tive element is a funcnon of thc bond strap dt ally do not spectfy consistently low levels resistivity, cross sectional area and length. where Z ~ strap impedance. cu ~ tacoma of bond impedance. nor a suitable test see Equation 1. whiht the inductive compo- frequency, V ~ voltage, and 1 ~ current.

method. The introduction of ncw EMC nent is a more complex function of thc bond From this. the higher thc inductance th speciGcations in Europe with the EEC strap characteristics as shown in Equation 2. more isolated the circuit or box become Directive on EMC and the requirements for from ground. Ths can have sigru6can R~- qf 0 j'f iong tenn stability in EMC characteristics effects oa equipment. inchding enhance has directed the UK nuTitary to review A ment of noise injecbon onto arcuits, reduc=

cidsutlg spcciEcaQons and Introduce a ncw Defence Standard to tighten up perfonn-

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ance requirements for nurttary equipment.

Dcf Stan (Part 1)/1 has been intro-L iZ, 2ic L

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+ 05+ 02235 j b+ c" 2f J non of Ster performance, and loss oi coaunlmication range. From a TEMPEST standpoint it may result in more radiation from emanent. lt would seem from this (2) ducal to address thia area as far as mob9e that the cntcria tor any bond is the and transpottablc canmunications installa- where R resistance, g ~ resistivity, f> inchlctancc and hence thc choice of short fat tions are conccnteia. but the requirements ~

length. A area, p, pcrmeabiEty of free shoukl have implications in industrial apph- space, L ~ inductance. p ~ feLttivc David Dugan served for 21 yean itt the cations and over the wlxHe ekctronics permcabiTity, b strap width, and c stttp Brrtiab Anny, where hc gained his Chgree market if long term product performance is thickness. ia dectricaf cnginceting. After service in a to be guaranteed. The frequency at which the inductive variety of appointments hc retired to join ekment dominates the impedance expres- the Recalls'ES company as the Techmca/

Bond Degradation sion when calcu!ating thc total inductance Mtnsgcr rcspottsiblc /or the cfes/gn and Earth or ground bonds are generaHy is, from Equation 3, typically 1 kHs. lt wgl devclopnsettt of commctttication systems.

considered essenual not only for safety be seen therefore that to al intents and fn 198$ he jainef Dytecna as the iManager reasons. but as a mean of diverting EM "

purposes thc bond except at DC and power of the &ginecnttg Division. and now ts currents, "locking" circuit boards and frequencies, may be assumed to be an currcntfy Tchtaica/ Marftcting Manage..

38 JulytAugust !991

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',:!0 iQ A. os JVA5Hf5 rrllt fR scarc 5 err VOUAGE &ifASI 'REhlENT Figure!. Bond resisurce. Figure 2. Four wire bridge method.

bond straps. However. an anaiys's of:he progressive degradation nt bonds, whilst current thc layers heat up and are vapo-bondinductancf shows Jiat I'or a bond strap the latter can reduce the ef'ciency of the rised. After the current is removed t.".e Sm of 100 mm!or g, 15 mm ~~de and 2 mm Ihck bond f;om the moment it is installed. It is can return. Thus high currert techmques the impedance at 1 MHa will be 3.8 Ohms. particuiariy important in communications are not recommended ror:esang EMI It sounds extremely sin:pie. but work systems, where 6lters are insuiied and bonds. The new Defence Standard in the performed in '.he USA'nd I:K shows that shielded cable ternunations are made Jiat UK speci6es a maximum probe voitage oi if an etrot is made 'in the way the strap is the bords are of ',ow resistance and reuin 100 mictovolts. This reprcsenu typically a ternunated then a progressive increase in their perfonnance. probe current ol 50 milliamps under shor

he resisunce of the bond strap to box citciit (< 1 mQ) condiuons. This -:s juncnon can occur as the equipment ages. Bond Performance and insuf6cient to destroy surface 5lms. The Eventuaily the resisunce will begin to Mtaalaremcnt chssic method for measuring low resisunce exceed hundreds of ohms and may eventu- Experience has shown over a number of has been to use a four:erminal bndge as ally go open c cuit. This can negate thc years that for long tenn consistent bond shown in Figure 2. In this case'the current effect of the bond strap completely as part performance a low value of resistance must is driven between two points and Ae of the E!rII protecdon.

tVhat happens with bonds to cause this change! Essentially a ground connecuon is In Def Stan ~

be achieved. This is typically 1-5 milhohms.

(Part 1)/1 the vahie has been set at a maximum ol 2 miUiohms. This VOltage aCtOSS the Sample iS meaSured witN a high resisunce probe. This removes Jie cfccts ot thc ptobe contact resistance and a series of irrpedances from thc strap level is measured through the individual lead resistance. This is generally consid-through to the grourd material, as shown bonds. Thc logic behind this level is ered to be a laboratory method as the use in Figure 1. Each point of contact contrib- twoloid. Firstly. experienc has shown that of four contacts can be awkward. If the lead utes to the total bond per'.onnancc;. As a with communicaions equipment in particu- resistance can be removed by a calibrauon result. a change in any contact condition can lar this value ol bond resisunce is required teclniquc then thc four terminals may be result in a change in the total bond if consistent performance is to be achieved replaced with a two terminal system.

resistance. As is weil appreciated, the" in terms of reception ef6ciency and trans- h further possible re6ncment to the contact resistance between two metal sur- mission characteristic. This is particularty tecluique is to use a frequency that is not faces is a hnction of the pressure. The so for TEMPEST protected equipments. DC or 50/60/iOOHx. In this case 10.4 Ha pressure exerted by the tip of a drawing pin Tbe second point is that if the bond has a haa been chosen. If an active 6lter is used is vastly greater than that from the thumb higher resistance then there is a signi8cant to Ster out a9 other electrica noise, then pressing by itself. Thus the contact from a likelihood that progressive degradation will it is posgblc to use the bond resistance sharp poult gives a tsoch higher prcssure occur and the bond resistance wig increase meter on powered up systems. It is worth t.'un a Oat point and 4gtiforc lower contact in value. There will then be a progressive noting that at this frequency the impedance resisuncc. Measutetata have shown that loss in perfonnance. ia stol htgcly represented by resistance sharp points enable Contact rcsisuncc of a The main problem with measuring bond rather than inductance. The two termmal few nicroohm to be achieved whilst similar resistances is that it should bc measured method is shown in Figure 3.

pressures on Oat surfaces result in mil- using a low voltage/curtent tcchtilquc, The introduction of new EMC/EMI liohms of conuct resistance. It might be Moat techniques to date for assessing spcci6cations in Europe has made it more felt that there is little or no difference driving a large current through the safety'nvolves important that once made the bonds have between these values, but in reality there bond. This checks the bond's abiRty to coils latent long 'tcrlil performance. Ths is. An essennai aspect of a good bond is carry current but does not necessarily check means measurin on periodic inspecnon ard that it should remain so after the equipment its EMI protection perfonnance. The rea- aRct maintenance. It is an essential aspect has entered usc. High pressures also have son is that many bonds may when in normal of insutmg consistent perfonnance. It has the effect ol squeesing out corrosive materi- use have a high resistance due to oxide and been shown that within months apparen Jy als and insulating 6lms. The former causes greasy 6lms. but when subjected to a high good bonds can deteriorate to .-igh resis.

EMC Test & Design

tance. Ther.io.e t.'i vces ii '-. ~

AAeqT suo)ect to testing and .xa.-..;.-.a:.cn-as a ma:ntenance tas~.

~ ic'oK ue45uI>eNr L K ~military Experience There have oeen '.wo ~ lcr -.::

caused by poor bonus expenence eiieo otsis ascg 0 degradauon .n ericrmance ~ready-uoned in:tus a.-.icle. The:oss i;cir, cation range. poor EMl pe.",'ormance other eifects aL'onrnbu'.e to a cons:dert reduction m equi".-..ent Nc:ency ann a.

ability. The secord ei;ect wnich is .

difficult to denufy:s:hat ai No Fault F.

(NFF) problems. An analysis of reN'."

failures from military reiiaLiity data .

shown that NFF inc:dents can ae extre..

high, particulariy:n hunud;timates.

FIXED RKSlSTANCE LEAOS has been partially confirtned by reports .':

the Gulf Sar when aH forces repor-.e.

increase in availability of equipmen: .;.

clunate. Many fau!ts are due to " 'rier electrica contacts in connectors. bu: a lar number have been idenufied as excess:

Figure 3. Two termmal bridge method. EMI induced through poor ground onnc This may be caused by either a loose groi strap or connector terminauon to:he ':c A significant improvement In equipme 4 4 availability and perfonnance is expec:e y when more recent statisucs are analysed.

The introduction:nto the Bnush Ar.-.

service of Ae Dyteaa Bond Resistanc I c<~~ 4c c>~ ~~c Test Set DT l09 has enabled the L":

mihtary to measure bond resistances installed equipment and reduce;he curances of NFF errors. The UK mi:ar measurement procedure uses a two:er-...:

nal bridge method and an accurate miiliohm calibration star. dard. This meas urement procedure and equipment is als in use by other NATO nations and e!se where by iniTitary and naval forces wro hav recognized the same problem.

Cottclueiotta The problems with ground bonds have become significant with the development o:

~ ( olnpi4lllA Q~+ c~ ~ (4 eeoc 4 ((i+ yo ~befit%

sensitive and secure communications equi"-

ment. This coupled with an increasing reed CUSTOMQAG Ti 4.++++" 9t ~o'4+ a ~~> t iQN to achieve higher and higher leveh of KMf CQMNC Rf AC. 0 odgot tc~ 'e+ b~+.=nuators, protectiwt has lead to an increased emphasis beng placed on the effectiveness of all types Coaxial Term.  %/@

~4. ~b,~

< y<c <4~ connectors, of systettt grounds. These. further com-bined with a requirement to ensure the long Cata ~pc+ q4 .attest life of systems once in service. have resulted in the assessment that bonds and lE terminations are one of the primary causes of EM faBures in systems. The require-11?0-1? bnCOln Avenue. FOlbrOOk.;4Y 11741 ment to test these is clear. however the (S16) ~85.)4tX1 FAX i16.~BR >l14 means to do so have not always been available to engineers.

INFO/CARO 29 40 July.Aug.st '.9o'.

Panel SessIon PES Summer Meeting, July lQ, 1988 Long Beach, CaHfornia John G. Kappenman, Chairman Power System Susceptibility To Induced. currents in the system, 2) the interconnected sys-tems tend to be more stressed by large region-to.region Geomagnetic Disturbances: transfers. combined with GIC which will simultaneously turn every transformer in the bulk system into a large reactive Present And Future Concerns power consumer and harmonic current generator and 3) in general, large FHV transformers, static var compensstors and relay systems are more susceptible to adverse influence and microperation due to QIC.

John C. Kappenman, Minnesota Power The effects of Solar. Geomagnetic Olaturbancea have been TRhNSFORMER OPERhTION observed for decades. on power systems. However, the pro-found impact of the March 13, 1989 geomagnetic distur- The primary concern with Geomagnetlcally-Induced Cur-bance has created a much greater level of concern about the rents la the effect that they have upon the operation of large phenomena in the power industry. power transformers. The three major effects produced by GIC in transformers Ia 1) the Increased var consumption ot the Several man.made systems have suffered d)eruptions to their effected transformer, 2l the increased even and odd harmon-normal operation d)aa to the occurrence of geomagnetic phe- Ica generated by the half. cycle saturation, and 3) the possi-nomena. Moat of the man~e systems, such aa commu- bilities of equipment damaging stray f)ux heating. As is weil nications, have brett made less susceptible to the phenom- documented, the presence of even a small amount of GIC ena through technological evolution (microwave and fiber- I20 empa or less) wN cause a large power transformer to optlc have replaced metall)c wire systems). However, the half-cycle saturate. The haif~c)e saturation distorted excit-bulk transmission system, If anything, is more susceptibl ~ ing current ls rich ln even and odd harmonica which become today than ever before to geomagnetic disturbance events. introduced to the power system. The distortion of the excit-And lf the present trends continue, it la likely the bulk trans- ing current also determ)nes the real and reactive power re-mission network will become more susceptible In the future. quirernents of the transformer. The saturation of the core Some of the most concerning trends are: 1) Th>> transmission steel, under haif~c) ~ saturation, can cause stray flux to en-systems of today span greater distances of earth-surface- ter structural tank members or currant wlndlngs which has potential which result In the flow of larger geomagneticaily- the potential to produce severe transformer heat)no.

IEEE Power Ealineeciag Review, October 1989 15

t I

tr:rscs'rr ei '- ry es. -e 'io:est 'esul!S trct ~

~ u ~ >> ~ ne ear!:i d, <<3g. 4!'

geonag,"et.'c storms when!hey are -' '- 4, 4 C 4 dra

~

de~~" ~

ste '.na; Stogie CnaSe sr 5.'"r-..erS;ai'CVCle Saturate muCn mere easilv ano!0 4 -"cn greater cegree;han ccrricarable

.;nree onase units.."ese:.ansformers produce higher mag. SUNSPOT CYCLES hND GEOMAGNETIC nnuces of harn onics and "or sume!arger amounts of rese- DISTLRBhNCE CYCLES

!rve power when comPareO with three phase deslgnS. On the average, solar activity. as measured by t."e nur oer ".

monthly sunspots. follows an 11 year cvcl'e. he "esen!

ItELhy HAND PROTECTIVE SYSTEMS sunsoot cycle 22 had its minimum tn Seoten.oer 1986. a."c is exoected to oeak in 1990-1991. Geomagnetic 'ela o 5 ~

>here are three ba5ic faitire modes of relay and protective tvrbance cycles do not have the same shaoe as:ne sunscot Svs!ems:nat can oe attr:buteo to ggeomaghetic distur- number cycles. even thOugh they are cyclical. F Sure snows 1 bances: the nature of the sunspot numbers and geomagnetic 3C!i"".v r

~ . alse Operation of:."e protection system. such as hav-ing OCCurreO rOr SVC. CabaCitar and line relay Opera- SurtsIre4 i 431 ~ 1444 4uit'ocr or tions where:t e!tow of harmonic currents are misin- C(rtworts

erpreter2 OV the reiaV aS a rault Or OVerlOad COnditicn. Cycle i7 Cycle la Cycle ia Cyote 20 Cyci ~ 21 Cctrs rrrr apr25 This is the most common failure mode. i I l irumoer el r i Olslureetd OdyVyear Suitspoi Humber ~

)40

~ Failure to Operate when an operation is desirable, this has shown to be a problem for transformer differential 150 t

120 protection schemes and for situations in which;he I

~

00 output of the current transformer is distorted. I I l00 j ii ~ ~ d0

~ Slower than Desired Operation. the presence of GlC Ii I can easily build up high levels of offset or remanent i de i

ttux in a current transformer. The high GIC induced off- 50 j, I r

I )

I ui I

i 40 set can significantly reduce the CT time.to.saturation I I

\

for offset fault currents. ~ 20 1

Most of the relay and protective system misoperations that ~ ~ . ~ 0

!400 35 ee cS 50 55 40 45 70 75 40 45 40 are attributed to GIC are directly caused by some malfunc-tion oue to the harsh harmonic environment resulting from Figure 1. Vaitstfons of the Yearty-Averaeed Sunspot Number enid large power transformer half-cycle saturation. Current trans- Qetsmaenettealty Olsturbed Oays from '1 932-1SBB.

former response errors are more difficult to directly associate with the GIC event. For exampfe in the case ot CT remen-encc. the CT response error may not occur until several days cycles from 1932 to 1988 i2, 3l. Note that the geomagnetic after the GlC event that produced the remanence. Therefore. dleturbanCe CyClee Can haVe a dOuble peak, One Of WhiCh Can these types of faitures are more difficult to substantiate. lag the sunspot cycle peak. While geomagnetic activity in the present cycle is expected to maximize in approximately 1993-1994, severe geomagnetic storms can occur at any CONCLUSIONS time during the cycle; the K-9 storm of March 13, 1989 was As evident by the March 13th blackout in the Hydro Quebec a striking example.

system and transformer heating failures in the eastern US, the power industry is facing an immediate and serious chal- EhRTHQURFhCE.POTENTIhL hND lenge. The power industry is more susceptible than ever to the influence of geomagnetic disturbances. And the industry GEOMhGNETIChLLY.INDUCEDWURREVTS will continue to become more susceptible to this phenome- The auroral electrojete produce transient fluctuations in the non untess concened efforts are made to develop mitigation eanh'5 magnettc field during magnetic storms. The earth is techniques. a conducting sphere and portions of ft experience this time-varying magnetic field, resulting in an induced earth-surface-potentlal lfSP) that can have vetuee of 1.2 to 8 volta/km t2 Geomagnetic Disturbance Causes to 10 volte/mile) during severe geomagnetfc storms in re-gions of low earth conductivity l4),

And Power System EEects flectric power systems become exposed to the 8 SP through the grounded neutrals of wye-connected transformers at the Vernon D. Albettsw2 opposite ends of long transmission lines, ae shown in Figure University of iiIJnaaota 2. The fSP acta ae an tdeal voltage source impressed be.

tween the grounded neutrate end has a frequency of one to a few mittfhene. The gsomagnetlcally-fnduced currents lGIC}

SOLhR ORIGINS OP GEOMhGNETIC STORMS are then determined by dividing the ESP by the equivalent dc The solar wind ie s rsrffied plasma of protons and electrons resistance of the paralleled transformer windings and line emitted from the sun. The solar wind fs affected by solar conductors. The GIC ls s ques%tract current, and values in flares, coronal holes, and disappearing filaments, and the so- excsee of 100 emperse have been rrNaeured in transformer lar wind paniclee interact with the eenh'e magnetic field to neutrals, produce auroral currents, or auroral etectrojste, that foltow generally circular paths around the geomagnetic pate! at al-titudee of 100 kilometers or more l1). The aurora borealis ie POWER SYSTEM EFFECTS OF GIC visual evidence of the auroral electrojets in the northern The psr.phses GlC in power transformer windings can be l6 IEEE Power Engineering Review. October 1989

1 ~

44 Ina ia.sat~tat.ah

~ n rich I:.tars gr~ers ause clay misoperat on tet REF EHENCES

~ 44 I

~ ~

1. Akasatu. S. I"The OyhtmiC Aurcra, 'ciehut C Ame":~

Al =.sr~ ti.RFACS 9 Mageziht. May 1989. pp. 90 97 T SARvii-SuRFACS <T5hti41. ~

~ 2. Induced 5aich. Surtact-Poitntial ISSP) Producing Qtamtg.

t'igui

2. Jactlyh. J. A.. "Reel-Time Ptedicuch ot Gfcbal Goon agr ti Activny, Saltr Wind Magnetosphere Cauphi'g, "p.

141. Tarrt Sciehuflc Publishing Company. oxvo. '986.

htticaliy Induced Cunehis IQICI in Power Sytttmt. 3 Thompsah. R. J., "The Amplitude at Saiar C.cie 22, Riidia ehd Space Sewiciis TtchhiCal Report TR 87 03, ctc bti 1987.

4 V. O. Albertgan ehd J. A. Vth Batten, "Utcuic phd hlaghe.;i many times larger than:he RMS ac magnetizing current, re- Fields at tht Stnh's Surface dut io Aurartl Cunenls." i55i sulting in a dc bias af transformer core flux, as in Figure 3. TcahaaCIiohs ah Power Apparatus and Systems. Val. PAS 39 hia. 2. April 1970. pp. 578-584.

5. J. Q. Kappehmtn, V. O. Albtrtaon. 9. Mohan. "Curser Trahatarmtr ahd Relay PtrtolmtnCt ih the Presence ot Gtc magnetically Induced Currents." ISEE Triiheactians ah Paw e~

Apparatus ahd Systems, Vai. PAS.100. No. 3, pp. 1078-1088. March 1981.

I I lo,pl I~ The Hydro-Quebec System Blackout Of March 31, l989 io.ai

<<ICI<<r~ Daniel Saulier, Hydro-Quebec On March 13. 1989. an exceptionally intense magnetic storm caused seven Static Var Carnpensators ISYC) on the 735-kY Rgurt 3. OC Btt! af Trtntfarmtr Cart Rulc Out to QIC. network to trip or shut down. These compensetors are es-sential for voltage control and system stability. With their loss. voltage dropped and frequency increased. This ted to systartt instability and the tripping of all the La Grande trans-The half.cycle saturation of transformers on e power system mission lines thereby depriving the HQ system of 9500 MW is the source of nearly all operating and equipment problems of generation. Tho remaining power system callapsed within caused by GIC's during magnetic storms. The direct conse- seconds of tho loss of the La Grande network. The system quences af the half-cycle transformer saturation ere: blackout affected ~ it but a few substations isolated anto lo-

~ The transformer becomes a rich source of even and cal gene~sting stations.

odd harmonics Pawer was gradually restored over a nine hours period. Oe-

~ A great increase in inducttve vers drawn by the trans- leya in restoring power wore encounterea because of dam-former aged equipment on tho La Grande n>>twark and problems with

~ Possible drastic stray leakage fiux effects in the trans- caid load pickup.

former with resulting excessive localized heating.

There are a number of effects duo ta tho generation of high SYSTEM CONDITION PRIOR TO THE EVENTS levels of harmonics by syatim power transformers. includ- Tatal system goneratfon prior to the events was 21500 MW.

ing, mast of it coming from remote power-generating stations at La Grande, Mantcouagon and Churchf8 Felts. Exports to Overloading ot capacitor banda

~ Possible rntsaperottan of relays neighboring Systems totalled 1848 MW of which 1352 MW were on OC interconnections. The 735-kV transmission net-

~ Sustained overvoltogos on lang. line energizattan wark was laded at 90% of tts stability limft.

Higher socondory arc currents during single. pole switching .

~ Higher cfratffC Maker recovery voltage SEQUENCE OF EVENTS

~ Ovorlaadtno of harmonic fttfyrs of HVOC converter ter- At 2:45 o,m. on March 13, a very intense magnetic storm minals, and dtotantan in tfio ac voltage wave shape ted to the conaequortttal trt p or shut down of seven SVC's, that may result in loss ot dc power transmission. Contafnlng tho impact of tho event through oporatar inter-The increased tnductfvo vora drawn by system transformers yention was impassible att SVC'a having tripped at caaaod to during halfwycl~ soturat)an are sufficient to cause intoler- function within o ano minute period.

abto system voltage depression, unusual swings in MW and A fow seconds l8-8 s.) after tho loss af tho last SVC, ~ II five MVAR flow on transmission linea. and problems with gener- 735.kV lines of the Lo Grande transmission netwark tripped ator var limits in some instances. duo to an out of step condition. These Itne trips deprived the In addition to the halt-cyclo saturation ot power trans- system ot 9500 MW ot generation and subsequently ted to a formers, high levels of GIC can produce a dlstarted response campteto system cat tapao.

17 IEEE Power Engiaeerintf Review, October f989

1

\

ecuon ance re~air ir 9 'cur SVC's snot sown ov caoac tor DIsturoances On Poiyer Transformers

~oitage uncaiance prctec::o." >>aivsis ot vootage ano cur.

rent osc:itograms taxen at:ne Ct ioougamau site before tne i

SVC tnps snowed tne '.oitowing narmonic contents.

Hooert J Hingjce O

~ James B. Stewart

.wC ,hC Current ar l6 ky Harnaiiic Vcliage Power Techttoloip'es Inc.

Order at .35 ky TCA Bracche TSC Brasche This discussion addresses the effects of geomagnet:c cistii" oances on power transformers. The primarv effect:s cue tc 100'"o 'Ã" I00~o core saturation resulting!rom geomagneticaltv incucea c r ~

9 of 36 ~o rents. GICs. Core saturation can imoose severe temoerature 1OO 24 ~

problems in windings. ieads, tank plate ana structurai mer.-

3'io I Oof

}6 ~o bars of transformers and place heavy var and harmonic oi.r ~

a ~ 5 Oof 5%

I ifo I ~ 16 ifo dens on the power system and voltage support equiprriant.

3~o 3~o a ff GIC's of 10 to 100 amperes are more:hen mere nuisances in tha operation of power transformers, the rnanr.er of !Iow Quasi DC currents generated by:he magnetic disturbance, can result in saturation of the core and consequent changes saturating in tne SVC coupling transformers are thought to in system var requirements. increases in harmonic curren.

be the cause for such a targe second harmonic component of magnituctes. increased transformer stray ana eady tosses.

currant in the TSC branch. and problems with system voltage control.

GENEAhL OBSEAVhTIONS ON THE SYSTEM CIC EFFECTS VERSUS CORE hND WIIOoDINC BEHh VIOA COiVFIGURhTIONS The system blackout was caused by loss of all SVC on I.a Principal concerns in this discussion are for EHV systems Grande Network. Seven SVC tripped or stopped functioning. with grounded Y transformer banks providing conducting Prior to and during the event all the OC interconnections be- paths for GIC and zero sequence currents. Cora and winding haved properly. No relay false trips or misoperation of special configurations respond differently to zero sequence open.cir-protection systems were observed. Telecommunications cuit currents end to GICa. Note: aa used here. the term "open ware not affected. No equipment damage was directly attrib- circuit"refers to tests performed with all delta connections utable to GIC but once the system split, some equipment waa opened or "broken." For example, the three. phase three leg damaged due to load rejection overvoltagea. core form transformers aro less prone to GIC induced satu-ration than three-phase shall form transformers. But. both core form and shell form single phase transformers are sus.

RF'VIEDIhL hCTIONS ThKEVi ceptibl ~ to GIC induced saturation.

Since the event. the following actions were implemented: Winding and lead arrangemanta respond differently to GIC

~ SVC protection circuits have been readjusted on four induced core saturation aa well. For example, the current dis-SVC's so as to render their operation reliable during tribution within pareil ~ I winding paths and within low voltage loads depends upon the leakage flux paths and mutual cou-magnetic storms similar work is being performed on pling. Loaaea within windinga and leads may change signifi-the four remaining SVC's, cantly under GIC induced saturation owing to the change in

~ Energy, Mines and Resource Canada now provides Hy- magnetic field intensity. H, and the resultant changes in the dro.Quebec with updated forecasts on the probability boundary conditions for the leakage field path.

of magnetic disturbances. Thaao forecasts are used by the System Control Center dispatcher to position the transmission system within secure limits. EDDY LOSSES IN STEEL MEMBERS

~ A.C. voltage asymmetry ia monitored at four koy lo- The changes in the magnetic intensity. H, and the magnetic cations on the system (Bouchorvitto, Amaud, LG2, boundary conditiona resulting from the GIC excttation bias Chhtgeaguay). Upon detection of o 3% voltage aaym- can increase tho loaaoa in steel plate, the losses for fields rnetry at any ona location, the ayotom control center parallel to the plane of the plato increase nearly aa the square dispatcher ia alarmed and will immediately ta'ko action of H. Note also that the level of losses increase approxi ~

to position system tranafor levels within secure limits mately aa the square root of the frequency ot H. owing to the if this haan't already been dane because of forecasted effect of depth of penetration. Tho magnetic field along yoke magnetic activity. clamps and leg plates in core form transformers and in Tee beams and tank plate In ahoN form transformers closely matches tho magnetic gradient ln tho core. Areas of the tank OPERhTING LIMNIDURING and core clamps are subjected to tho winding leakage field.

MhGNETIC DISTURShNCES If the coro saturates, the magnetic field impressed upon the (hND hLERT SITUhTIONS) steel members may rise ton to one hundred times normal duo to the saturation and the offocto of the leakage field. The The fallowing operating limits are now being appliedt loaaoo in the stool momboro will riao hundreds of times nor-mal, even under half-cycle saturation. On tho steel surfaces.

~ 10% safety margin shall be applied on maximum trans-fer limits. eddy lose density moy rise ton to thirty watts par square inch,

' approaching the thermal flux density ot an ~ lactric range ele.

Maximum transfer limits shell not take into account tho ment.

availability of static componaators deemed unreliable.

~ Adjust the loading on HVOC circuits to be within tho Surface temperatures riao rapidly with this thermal flux and 40% to 90%, or loaa. of tho normal full load rating. can result in degradation of insulation touching tne steel l8 IEEE Power Eatpaeeriag Review. October l 989

r Ocl lr lent vendor Destgn Ocf tcfency aafma1 UPS haS Vendor no battery naINIa1 test na int enanc e CI I'CUI t sect loA docs AOI QCAt I OA batteries.

Battefies have not been Design Deficiency replaced in Design Deficiency 6 ycafs k.S relay Back up charactertst- Breaker batteries ICS PfCveAtS ffcIct ion AC degraded or transfer to per design input to dead inverter logic poucr output.

salty is naihtchahcc preferred Ground Vol tagc AC pouer to logic trips Breakers ups loads fault occurs on traflicnt logic nodule OA poucr 2VSS UPStA,S, CS-I,2 3 do hot auto loss of all phase of aain oA stat lofl for UPStA.D,G out pu'I SISIPty C,O,G trip open; Ch-C transfer to loads on B

transfofncr AC pouer cspcrIchccs voltage failure. does not mint. UPS1A D,ri steeply the transient goes tou close supply Pernisstves Faul t prohibIt CS C 1$ clcafcd breaker froze in 6 cycles; clo>Ing transfer cocptetcd in 12 cycles CS'4 ncsvh<

to If unsfer na Int sullpl y to lnvcl tcf out put

r

1. Static DC testing was performed on individual chips from the effected circuits in order to characterize Latch-up susceptibility.

Static testing is performed with fixed voltage settings. The testing was performed on the 4049, 4011, 4044 and 4068 devices.

The test scheme included:

A. Output voltage below Vss (Vss is the ground or negative power supply).

B. Output voltage above Vdd (Vdd in the positive voltage power supply).

C. Input voltage above Vdd.

D. Power supply overvoltage. Vss>>Vdd The testing revealed that permanent physical damage was induced by tests C and D. Test B did not induce latch-up but test A consistently induced latch-up on the 4049 and at higher voltage differentials on the other devices- The 4049 was quite sensitive to this test.

2. Voltage Dropout testing, where the Vdd was cut out and restored during time periods ranging from 20 mS to 2 seconds did not result in latch-up behavior on the individual components.

A "breadboard" test circuit was fabricated to simulate a typical circuit path, i.e. a 4044 latch driving a 4049 invertor driving a 4068 gate driving a 4011 gate driving an MC1615 lamp driver.

Slow rate dropout testing of the test circuit did not result in latch-up or other anomalous behavior.

3. Board level testing has been performed on the A13A21 cards f'rom UPS units A, B and G. A stock card has also been tested. A test fixture was fabricated to hold the cards and supply paver and input selection and output monitoring. An MC 1615 lamp driver chip with LED's (light emitting diodes) was connected to the card outputs.

Static boaef testing revealed no anomalies on the A card, a damaged U10 4049 oN the B card, No anomalies on the C card and a failure to set, any of the 4044 latches on the G card. (Note that latching of the 4044 chips is normal while latch-up is an abnormal condition.)

The. functional failure of the G board has been traced to the Kl relay and/or the SW 1 reset svitch on the circuit board.

Failure simulation testing on the functional A board has revealed that the lighting pattern reported during the incident, whero the lamps on the card were extinguished and "downstream" lamps remained e

illuminated, has been duplicated by setting the PSF-not latch, lowering the DC voltage to approximately 4 VDC and lifting (floating) the DC ground for several seconds. If the DC voltage remains low after the ground fault the lamps on the board will reset and the external lamps (UPS fail, Logic fail and the SSTR lines) will remain illuminated. The simulation conditions are unlikely to be those of the failure event, however, it demonstrated that the board can operate in an this illogical state.

has been A more complicated failure simulation (approximating the actual event) may produce the same results.

4. High Speed transient. testing on the power lines is planned and delayed pending laboratory analysis of the degraded samples discussed in the following section.

M C 0 A. NEGATIVE VOLTAGE ON THE OUTPUT OF THE 4049 MILL INVARIABLY CAUSE LATCH-UP- INJECTING NEGATIVE VOLTAGE INTO THE OUTPUT IS IDENTICAL TO RAISING THE GROUND Vss ABOVE THE OUTPUT.

B. THE INITIALFAILURE CONDITION IN TERMS OF THE LAMP SETTINGS CAN BE DUPLICATED UNDER UNLIKELY CONDITIONS AND MAY BE POSSIBLE UNDER MORE PLAUSIBLE CIRCUIT CONDITIONS.

The following samples have been submitted for laboratory analysis:

1. One battery pack. Battery pack 1 from UPS 1C.

(2) integrated circuits from a failed A20 card.

n'.

Two A 4049 and a 4011.

3. A failed U10 4049 from the A13121, UPS B card.

4. The U10 4049 from the A13A21 cards from UPS's A and G

5. The UPS 6 Kl relay and SWl switch.

The following results have been obtained.

1. Two (2) of the Three (3) batteries from UPS 1C were dried out.

Water was added and charging did not result in recovery of the cell. It is concluded that the cell failed due old age wearout.

Analysis is continuing on the other two (2) cells.

2. The 4011 from the A20 card is electrically good. Internal

I J

~ ~

I

. inspection of the Die revealed no anomalies. The 4049 is lj

~

~

~

~

'electrically bad. A catastrophic failure. Internal inspection of the die revealed severe damage centered on the Vss and Vdd power lines and several input/outputs. The initiating overstress was introduced on the Vdd or Vss lines as indicated by arc-over damage acoss the oxide between the two power lines.

3. Electrical testing of the U10 4049 from A13A21, UPS B revealed that it was not functional. Internal inspection of the die revealed a fused aluminum metallization line to one part of the internal circuitry. Probing revealed no )unction damage on either side of the fuse site. This damage is characteristic of classic SCR latch-up.

4. Electrical testing of the two (2) additional 4049's was performed during circuit board test. The devices were functional.

Internal die examination revealed no damage on either device.

5. Electrical testing of the A13A21 circuit board from UPS G revealed that SW1 was intermittently open circuited in the normally closed position. This condition would provide continuous reset signals to the 4044 latches through the K1 relay. The switch was isolated and a good switch was placed across the Kl relay. The circuit board inputs still would no latch the lamps. The Kl relay was removed and testing revealed that it was electrically good. The findings reveal that either the Kl relay is either intermittently bad or there are other problem components on the circuit board.

Analysis is continuing.

R 0 U 0 A. THE DAMAGE NOTED ON THE 4049 FAILED INTEGRATED CIRCUIT FROM UPS B WAS INDUCED ON THE Vss (GROUND) SIDE AND SUGGESTS A GROUND TRANSIENT MAY HAVE OCCURRED. THE DAMAGE ON THE 4049 FROM THE A20

. BOARD INDICATES THAT THE DAMAGE WAS INITIATED BY A TRANSIENT ON EITHER THE Vdd OR Vss LINE, BUT IT MAY ALSO HAVE BEEN INITIATED BY LATCH"UP.

B. AT LEAST ONE OF THE BATTERIES FAILED DUE TO OLD AGE WEAROUT.

C. THE CAQNE OF THE FAILURE OF THE UPS G TO SET THE LATCHES ZS UNKNOWN AT THIS TIME. THE SW SWITCH HAS BEEN FOUND TO BE DEFECTIVE AND ANALYST'S WILL DETERMINE IF THE COMPONENT IS RELIABILITY RISK.

I

-UPS lA 1B 1G TEST

SUMMARY

page 1

Purpose:

To prove that the DC logic power for the Exide UPS is powered from the B-phase maintenance supply. The K-5 pickup and drop out voltages and the DC trip-point o=

the DC logic will be recorded for UPSlA, not for UPS13 and UPS1G. The internal batteries will be tested and replaced.

Results Summary:

1.) On UPS1A, logic UPS1B and UPS1G, it was verified that the power supplies are fed from the B-phase DC maintenance supply.

2.) The K-5 relay drop out and pick up voltages were recorded for UPS1A and they were found to be below the trip point of the DC logic power.

3.) On UPS1A, UPS1B, UPS1G, the maintenance supply was opened with the UPS feeding the loads and no UPS trips occuzredo 4.) On UPSlA, UPS1B and UPS1G, the batteries were replaced.

CONC U This test proves that the DC logic power is fed by the B yhaae maintenance power. It proves that the internal it proves that batCOries were effectively dead. For UPS1A on a slow transient that. the DC logic power will drop out before the K-5 relay will transfer to UPS power.

page 2 Numerical Results:

1.) The UPS1A DC logic trips at <16.7 VDC. (with.75.6 VAC on input) .

2. ) UPS1A: K-5 relay drop out 47 VDC K-5 relay pick up - 52 VDC 4.) The internal battery voltage was measured:

UPS1A: Positive-Negative-UPS1B: Positive- 0.54 Negative- 6.2 UPS 16: Positive- 18.3 Negative- 0.69

) J 2VBB-UPS1C TEST

SUMMARY

page 1

Purpose:

To prove that the DC logic power for the Exide UPS is powered from the B-phase maintenance supply and that a transient occurs on the maintenance supply it can if effect the DC logic such that it will trip the unit.

This test is done with the old internal logic batteries and then repeated with new ones. Each of the inverter trips will be tested to verify that each circuit is still intact except DCOV., An AC input transient to UPS will be simulated to verify that the unit can "ride out" a normal AC input transient without tripping. The K-5 relay pick up and drop out voltages and the DC trip-point of the DC logic will be recorded.

Results Summary:

1.) Zt was verified that the DC logic power supplies are fed from the B-phase maintenance supply.

2.) A rapid open and closing of the upstream normal AC input breaker to the UPS was done and the unit did not trip or go on battery. No noticeable effect was seen on the UPS output.

3.) Each inverter trip circuit except DCOV was tested and each functioned as designed.

4.) Fast transient tests:

With the old batteries still installed a voltage interruption of 100 - 150 msec duration was given to the AC input to the DC logic of UPS1C. The DC logic was initially at 19.86 VDC. The unit tripped 3 out of 4 times. This was done first with the loads on

. xaintenance supply and then also with the loads on UPS power ~

With the new batteries installed there was no trip when the fast transient test was performed 25 successive times. There were no trips but a repeated SCR short alarm occurred which is indicative of noise spikes within the unit.

page 2 5.) The K-5 relay drop out was recorded and was found to be below the trip point of the DC logic power.

6.) Normal transfers were done, UPS to maintenance and maintenance to UPS, with dead batteries and there were no trips of the UPS. The maintenance supply was opened with the UPS feeding the loads and no UPS trips occurred.

CONCLUSZON This test proves that the DC logic power is fed by the B phase maintenance power and that it is susceptible to voltage transients on the maintenance supply. Zt may be susceptible to other transients as well because it is directly tied to maintenance supply. The test DOES NOT prove the level of susceptibility, that is, it does not prove that the transient was of any set voltage or duration.

The test implies that the batteries may have mitigated the trip but is not conclusive.

Each trip circuit was tested successfully so no failure to any of these occurred that caused the trip.

The fast open/close of the normal AC input breaker proves that the unit would withstand an AC input transient without failure or without going on battery power.

I

'5 ~

page 3 Numerical Results:

1.) Fast Transient Tests a.) W't existin batteries 1.) With loads on maintenance:

At 19.86 VDC (90.0 VAC) - ~tri (150 msec.)

At 19.86 VDC (120 VAC) - ~t '150 msec.)

2.) With loads on UPS power:

2 Tries, 1 ~t i (200 msec.)

b.) W't new batter'es-1.) Approx. 20.0 VDC - 25 times,

~no tri . (100 msec. )

2.) The DC logic trips at < 16.9 VDC. (with 84.59 VAC on input).

3.) K-5 relay drop out -- 45 VAC K-5 relay pick up ** not recorded 4.) The following trips tests were done:

a.) OV/UV b.) ACUV c.) ACOV d.) DCUV e.) Frequency fail f.) Logic Failure g ) Power supply failure

h. ). Clock failure 5.) The internal battery voltage was measured:

Positive - +0.6 Negative - +0.04

4 l ~

5

page 4 5.) Xndividual cell voltages:

Batte Volta e New Batte Volta e 1.) 1. 19 6.10 2.) 2.48 6.07 3.) 2.24 6.10

4. ) 0.17 6.09 5.) 0.79 6.10 6.) 1.78 6.12

V -UP D S S page

Purpose:

To prove that the DC logic power for the Exide UPS is powered from the B-phase maintenance supply and that a transient occurs on the maintenance supply it can if effect the DC logic such that it will trip the unit.

This test is done with the old internal logic batteries and then repeated with new ones. The K-5 pickup and drop out voltages and the DC trip-point of the DC logic will be recorded.

Results Summary:

1.) It was verified that fed from the B-phase the'C logic maintenance power supplies are supply.

2.) Fast transient tests; With the old batteries still installed a voltage interruption of 100 - 150 msec duration was given to the AC input to the DC logic of UPS1D. The DC logic was at 20.9 VDC. The unit would not trip. The AC input voltage to the DC logic was then reduced such that the DC logic was at 20.0 volts. When the test was performed with the DC logic power at 20.0 VDC the unit tripped. This was done first with the loads on maintenance supply and then also with the loads on UPS power.

With the new batteries installed there was no trip when the fast transient test was performed though there was significant hits shown on the DC logic power bus as seen by the oscilloscope.

3.) The K-5 relay drop out and pick up voltages were recorded and they were found to be below the trip point

. of the DC logic power.

4.) Normal transfers were done, UPS to maintenance and maintenance to UPS, with dead batteries and there were no trips of the UPS. The maintenance supply was opened with the UPS feeding the loads and no UPS trips occurred.

I a

pl lt i1 4i V

, ~

page 2 CONC This test proves that the DC logic power is fed by the B phase maintenance power and that it is susceptible to voltage transients on the maintenance supply. It may be susceptible to other transients as well because it is directly tied to maintenance supply. The test DOES NOT prove the level of susceptibility, that is, it does not, prove that the transient was of any set voltage or duration.

The test implies that the batteries may have mitigated the trip but that is not conclusive.

ta 0

page 3 Numerical Results:

1.) Fast Transient Tests a.) W't e istin batteries With loads on maintenance:

At 20.9 VDC five tries, no trips.

At 20.7 VDC - one try, one ~tri . (150 msec.)

2.) With loads on UPS power:

At 20.06 VDC - one ~t ' (100 msec.)

b.) W't new batteries 1.) At 20.05 VDC - Five tries, hit

~so tri s.

noticeable DC on each transient.

2.) The DC logic trips at <17.3 VDC. (with 84.5 VAC on input).

3.) K-5 relay drop out -- 42 VDC K-5 relay pick up 55 VDC 4.) The internal battery voltage was measured:

Positive- +0.6 Negative- +0.14 (the negative battery set was actually slightly positive).

5.) individual cell voltages:

t V tae w Batte Vo ta e

.254 6 '0 2.) .570 6 '6 3.) 1.03 6 ~ 10 4~) .07 6 '0 5.) 1 ~ 17 6 '3

t 0

I t

6.) 1.39 6 '9

1 resulted until such time the power to these UPS's was restored. However, one or more of the other lighting systems namely, emergency, normal and 8 hour9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> battery pack were available in these a'reas during this event.

The stairwells are provided with essential lighting only except where 8 hour9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> battery pack lighting is added for Appendix R compliance. Illumination to these stairwells was not available due to loss of normal UPS.

The 8 hour9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> battery pack lighting did not energize because there was no loss of normal power.

Event Evaluation The root cause of loss of power from normal UPS is evaluated separately in another report. During the event, some areas of the plant lost partial illuminations provided by essential lighting for sometime. Areas critical for safe shutdown where this lighting are identified are provided in Attachment 7.

During this event the plant was safely shutdown from the control room. Because the control room is provided with adequate lighting without the essential lighting, loss of essential lighting did not adversely affect the operator actions needed to bring the plant to safe shutdown.

The access route used by the operators during this event for restoration of the normal UPS power (Attachment 8) supplies was illuminated from normal lighting except for the stairwell where portable handheld lights were used. (FSAR Sec. 9.5.3.3 allows the use of portable lighting in the form of handheld flashlights for short excursions into the plant). The normal UPS locations were illuminated by normal lighting. Therefore, restoration of UPS power was unaffected by loss of essential lighting. Even though the essential and egress lighting are powered by three normal UPS's, this event due to multiple

'ailures of allduring, normal UPS's, essential and egress lighting systems were not available. The existing essential and egress lighting design is adequate, however, the root cause of the multiple failures of the normal UPS's will be determined/evaluated and appropriate corrective action taken if required to ensure that multiple normal UPS's failure will not reoccur.

reliability of stairwell lighting where will The proposed plant modification 89-042 enhance the 8 hour9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> battery pack lighting is provided.

NSK2 14

Status of Normal Reactor Buildin Li htin During the event on August 13, 1991, it was reported by the operators in the reactor building that some areas of the reactor building lost lighting momentarily.

Event Evaluation Normal lighting for reactor building general areas, work area's and electrical equipment areas is provided with low wattage high pressure sodium vapor lights. In the event of power interruptions or voltage dip lasting for more than one cycle, these fixtures extinguish and do not restart until the lamp cools and pressure decreases. When a power supply to continuously energized sodium vapor light is interrupted, it has a cooldown period before a restrike of the lighting can occur. The cooldown period depends upon the rating of the light bulbs. During the event, the emergency distribution system experienced a,transient due to the fault on the Phase B main transformer. During the event, the Reactors Building normal lighting in certain areas where these high pressure sodium vapor fixtures are provided, was interrupted for approximately 30 seconds. This momentary loss of lighting was due to the inherent design of low wattage high pressure sodium vapor lighting which requires cooldown period prior to restrike whenever power is interrupted. The same scenario could occur in the plant wherever power supply to high pressure sodium vapor fixture is interrupted momentarily, however, there is no indication of such a loss in other areas of the plant. Therefore, it is consistent with NMP2 lighting design and USAR Section 9.5.3.

h) Grou 9 Isolation Valves Closure The group 9 primary containment isolation valves are part of containment purge system. These valves are listed in Technical Specification Table 3.6.3-1, Page 3/4 6-24 and USAR Table 6.2.56, Page ll of 24. The function of group 9 isolation valves is to limit the potential release of radioactive materials from primary containment. These isolation valves are opened during power operation only at infrequent intervals to allow injection of nitrogen into primary containment to inert or de-inert the primary containment at a desired pressure. These valves, if open, receive signal to close if any of the following happen:

NSK2 15

a) High radiation through standby gas treatment system (SGTS). The SGTS radiation monitor located in the main stack is designed to continuously monitor offsite release and provide isolation signals to these isolation valves.

b) High drywell pressure.

c) Reactor low water level.

d) Manual isolation of main steam isolation valves.

Event Evaluation During this event, the group 9 primary containment isolation valves closed. This isolation is the safe mode of operation limiting potential releases of radioactive material from primary containment.

The initiating condition for these valves occurred as a result of loss of power to radiation monitor 2GTS-RE105 when UPS power to the DRMS computer was interrupted.

The actual isolation occurred when the logic was reenergized upon restoration of the UPS power supply to the monitor's auxiliary relay circuit. Therefore, group 9 isolation valves closed as designed and is consistent with USAR Section 6.2.5.2.4, Page 6.2-77.

j) Reactor Manual Control S stem The reactor manual control system (RMCS) provides the operator with means to make changes in nuclear reactivity via the manipulation of control rods so that reactor power level and core power distribution can be controlled. This system is a power generation system and is not classified as safety related. The RMCS receives electrical power from the 120 V AC normal UPS.

The RMCS does not include any of the circuitry or devices used to automatically or manually scram the reactor. The RMCS control and position indication circuitry is not required for any plant safety function nor is it required to operate during any associated DBA or transient occurrence. The reactor manual control circuitry is required to operate only in the normal plant environment during normal power generation operations. The discussion of RMCS is consistent with USAR Sections 7.7.1.1, Pages 7.7-1, 2, 14.

NSK2 16

Event Anal sis The RMCS was lost during this event because its power source, the normal nonsafety related UPS, was lost.

The loss of RMCS is not a concern during this event.

Since the plant was automatically scrammed during this event, the RMCS need not perform any function after the scram. This RMCS is used by operator only during normal plant operations. Therefore, if the plant had not automatically scrammed during the event, loss of RMCS would not have caused a safety concern based upon the following:

EOP's provide guidance to the operator under situations involving failure to scram, and

2) various ATWS mitigating design aspects of the plant were fully operable throughout the event.

Although this system was lost'during this event, its importance diminished once the automatic scram occurred. Therefore it is concluded that the RMCS function was consistent with USAR Section 7.7.1.1.

k) Feedwater Control S stem The feedwater control system controls the flow of feedwater into the reactor vessel to maintain the vessel water level within predetermined limits during all normal plant operating modes. During normal plant operation, the feedwater control system automatically regulates feedwater flow into the reactor vessel. The system can be manually operated. The feedwater flow control instrumentation measures the water level in the reactor vessel, the feedwater flow rate into the reactor vessel and the steam flow rate from the reactor vessel. During automatic operation, these three measurements are used for controlling feedwater flow.

The feedwater control system receives its normal power supply from the normal UPS. The feedwater control system is designed to lock in its last position upon a loss of power to its control electronics. The feedwater control system is discussed in USAR Section 7.7.-1.3, Page 7.7-23.

Event Anal sis During this event, upon loss of the normal UPS's, the feedwater control system performed as designed and failed in its last position. Therefore, it is concluded that the feedwater control system function was consistent with USAR Section 7.7.1.3.

NSK2 17

h

'1

l) Feedwater Pum Tri Feedwater is provided to the Reactor Pressure Vessel (RPV) via the Condensate Pumps', Condensate Booster Pumps and the Reactor Feed Pumps shown in Attachment 9.

The Condensate Pump draws condensate water from the Condenser and provides the necessary Net Positive Suction Head (NPSH) for the Booster Pumps. The Condensate Booster Pumps provide the necessary NPSH for the Reactor Feed Pumps. A minimum flow control header is provided off the discharge header of each pump to ensure that the minimum flow is maintained through the associated pump. The minimum flow control valves and associated instrumentation actuates to maintain this minimum flow. The main feedwater control valves (LV10), located on the discharge header of the Reactor Feed Pumps, modulate to control reactor water level.

The feedwater control system is powered by normal UPS power supplies. The above discussion is consistent with USAR Section 10.4.7.

Event Evaluation It was reported during this event that feedwater pumps tripped. An evaluation of this condition reveals that reported happenings are consistent with the system as designed and is in consistence with USAR Section 10.4.7. The instrumentation controlling the minimum flow recirculation valves on the condensate, condensate booster and the feedwater pumps is powered from the normal UPS's. These instruments are also designed to open the valve upon loss of power in order to protect the pumps. Upon loss of normal UPS, the feedwater control valves fail locked in their last position.

Following the turbine trip, an ATWS signal would attempt to drive the feedwater control valves closed, however since an ATWS signal was not present, this did not occur. With the feedwater control valves failed locked and the minimum flow control valves (FV2) driven full open, feedwater flow increases and approaches pump run-out. The Reactor Feed Pump NPSH decreases to the low-low pressure trip point, tripping the Feedwater Pumps. The Feedwater pump control circuit does not utilize an auto transfer logic to standby Feedwater Pump; therefore, feedwater flow is lost. The instrumentation circuits for all other minimum flow control valves are also powered by normal UPS power supplies. These valves all fail in the open position with the loss of UPS and contribute to the loss of Feedwater pump and condensate booster pump. This is consistent with USAR Section 10.4.7.

NSK2 18

'I I

m) Annunciators and Com uters The plant annunciator system provides information to the plant operators by windows located on the main operator panelboards and on back panels within the Power Generation Control Complex (PGCC). This system does not include annunciators on local panels throughout the plant and on special panels, e.g., fire protection, within the PGCC. The plant annunciator system is non-safety related and is connected to the normal power distribution system through normal UPS's. The plant annunciator system is not discussed in the USAR.

Several computer displays, with inter-active keyboards, are located in the PGCC. These displays are from the following computer systems.

PMS Plant Process Computer LWS Liquid Radwaste Computer, which has the following subsystems:

LWS Liquid Radwaste Control GENTEMP Generator Temperature Monitoring ERF Emergency Parameter Display System SPDS Safety Parameter Display System DRMS Digital Radiation Monitoring System 3D Monicore A system used primarily for core calculations and monitoring In addition, noble gas information is provided to the plant operators from the GEMS (Gaseous Effluent Monitoring System) computer by chart recorders on a back panel; and the operators have access to the GETARS (General Electric Transient Analysis & Recording System) computer.

All of the above computer systems are non-safety related and are connected to the normal power distribution systems through normal UPS's. There are some safety related radiation monitoring skids that provide input to the DRMS computer. However, these skids also provide safety related indication in the PGCC that is independent of the DRMS computer.

NSK2 19

The Plant Process Computer is discussed in Section 7.7.1.6 of the USAR, where it computer is non-safety related.

is mentioned that the USAR Section 11.2.1.2 covers the Liquid Radwaste System design basis and states that the power supply for all Radwaste System components is provided from non-Class 1E power sources. This is compatible with the Safety-Parameter Display requirements since NUREG-0737, Supplement 1 states that the SPDS need not be qualified to Class 1E requirements.

The process and effluent radiological monitoring and sampling systems, which include the DRMS and GEMS computers, are discussed in USAR Section 11.5. This section defines which monitors are safety related and which are non-safety related. The DRMS and GEMS design complies with this USAR section.

Area radiation and airborne radioactivity monitoring instrumentation, which include the DRMS and GEMS computers, are discussed in USAR Section 12.3.4.1.

This section defines which monitors are safety related and which are non-safety related. The DRMS and GEMS design complies with this USAR section.

A description of the 3D Monicore computer system was added to USAR Section 7.7.1.6 by LDCN U-1235. This LDCN states that the 3D Monicore system is non-safety related.

The designation of the computer systems mentioned above as non-safety related is consistent with the explanation of the Uninterruptible Power Supply System in USAR Section 8.3.1.1.2. In this section it stated that 2VBB-UPS1A feeds the radwaste computer is hardware, 2VBB-UPS1B feeds local non-safety related radiation monitoring microprocessors, and 2VBB-UPS1G feeds plant computer loads.

Event Evaluation With the loss of the normal UPS's, the plant annunciation system and the computer systems listed above became inoperative due to the loss of power.

This is consistent with the plant design and the description of the plant in the USAR. These systems are non-safety related and, hence, are not required to shut down the plant following a design basis event.

NSK2 20

CONCLUSION Based on responses the above evaluation, during the event on it can be concluded that the plant 8/13/91 is consistent with USAR descriptions..

RECOMMENDATIONS Based on the above evaluation, the following long term recommendations are provided.

1) Plant Oscillograph The in-plant oscillograph should be replaced with a more reliable and functional unit.

If this oscillograph was functional during the event on 8/13/91, adequate data could have been available to accurately evaluate the cause of the disturbance.

2) Essential Lighting The proposed modification 89-042 should be implemented as soon as possible to enhance the rel'iability of stairwell lighting where 8 hour9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> battery pack lighting is provided.

3) Control Power Supplies During the Electrical Distribution System evaluation, it was revealed that most of the systems important to plant operations such as feedwater system, annunciation system, etc, receive their control power from either normal UPS 1A, 1B or both. It is recommended that control power supplies for these systems be evaluated and reconfigured to avoid plant transient due to loss of single normal UPS.

4) Main Generator visual inspection Itbe isperformed recommended that of the a thorough generator stator and winding support system during the next refueling outage (see Attachment 10).

NSK2

345KV TO Sl "A STATION LINE 23) ATTACHMENT'-1 345/25KV 115KV SOURCE 'A'LINE 5) UNIT SPARE 115KV SOURCE '8'LINE 6) 115KV SOURCE 'B'OR TRANSF.

498HVA EACH UNIT

'8'UX 25KV~ 42/56/79MVA 'A'2/56/78HVA RESERVE

~NORMAL STA. TRANSF.

24.')KV/13.8KV RESERVE BOILER BANK 'A' BANK 199-59/59HVA WJGKV NO CUB ONLY CUB. ONLY 2NPS-SWG991 2NPS-SWG993 13.BKV NORHAL .

~ 13.BKV AUX. BOILER BUS 2NPS-SWG892 AUX. TRANSF. AUX. TRANSF. NC NO NORHAL 4 J69KV 2NNS-6WG914 4 J6KV 2NNS-SWGBII 2NNS-SWG812 2NNS-SWG913 2NNS-SWG91 5 WJGKV ~

0.16K V NO STUB BUS STUB BUS CUIL ONLY NC iJ69KV OIV.I EHERGENCY 2ENSiSWGIB) 2ENS~SWGI92

~ 4.169KV DIV.3 EHERGENCY BUS 2ENS~SWG193 4.168KV OIV.2 EMERGENCY BUS EGI OIV.1 4489KW EG2 DIVE EG3 BID 2688K W 4489KW ONSITE A.C. POWER SUPPLY

5 BIIKLE LQK FOR NN-IE tPSIA IILICJOol(LI)L3(L38 2NPS-SWGB8) ONV) 2NPS-SWG883 03.8KV) 2NPS-SWGBBI a@SKY) 2NPS-SWGM3 (688 V) 2NJS-US4 (688 V) 2NJS-US3 2NJS-US3 2VBB-TRSI 2NJS-USI 2NJS-US4 BUS A BUS 8 AUTOHATIC BUS C BUS 8 TRANSFER SWITCH (688 V) (6MV) (688 Vl (688V) (688V)

~ INTERNAL 2NHS-NCC996 2LAT-PN.388 2VBB-PNL381 BATTERY NO 2LAT-PNL188 2NJS-PIL482 BUS A ALTERNATE N N N AS UPS UPS UPS UPS UPS BAT-IC UPS BAT-18 UPS IO BAT-IA IC BAT-IA IA BAT-IC BAT-IC IN ~ 3A 3B BAT IB A A N (6BSV) (688 V) (688 V) (6MV) (688 V) (688 V) 2NJS-US6 2NJS-USS 2NJS-US6 2NJS-PNL')81 2NJS-PNL5M 2NJS-PNL688 HJGKV) H J6KV) (4 JSKV) (6MV) (688V) (6MV) 2%S-SWGBIS 2NNS-SWG914 2NNS-SWG815 2NHS-HCCB)6 2NJS-USS 2NJS-US6 BUS B 03J)KV) 03.8KV) 0XSKV) (689 V) (4 J6KV) H J6KV) 2tfS-SWGM3 2NPS-SWGBBI 2NPS-SWG883 2NJ6-US') 2NNS-SWG814 2NNS-SWG915 BUS 8

- OXSKV) 03J)KV)

SINGLE LINE FOR CLASS IE LES 2(L2B 2NPS-SWMBI 2NPS-SWG883 H JSKV) H JQOO 2ENSiSWGIBI 2ENS+SWG)83 (688 V) (6MV) 2E JSiUSI 2E JSiUS3 (6MV) 2EJS+PNLIBBA 2E JSiPNL38BA BAT-2A UPS BAT-28 UPS 2A 28 (6MV) (688 V) 2LACiPNLIMA 2LACiPNL3M8 (688 V) (688V) 2EJSiUSI 2EJSiUS3 (4 J6KV) H JGKV) 2ENSiSWGI91 2ENSiSWGI93

3889.5A 3898-SA 2SPUY82 2SPUZBI 86-1 P 866 HEA 3889-5A I 3898-SA 3BM-SA [ 6 2SPMXBI I pe66~HEA I 22-2YXCNBI 86-1 1289-SA I 2SPMZBI 59 I P864~HEA 51 pe66 IAC P866 HFA 2HTX-HIA 2MTX-HIB 2MTX-HIC 2HTX-MID HAIN XFHR SPARE I P864~HEA 292KV-24~KV 498/457MVA OA/FOA 63-1 63-1 63 63 63-4 63-4 PSa< ~MFA pe65 HGA pe65 HGA pe65 HGA pe65 HGA 87

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LIST OF PROTECTIVE RELAY ACTUATED ON AUGUST 13 1991 Unit Protection Alt 1 Protective Rela Lockout Rela Action Ref. Dwg, 87-2SPMX01 86-1-2SPUX01 ~ Initiate Turbine Trip ESK-8SPU01 Main Transformer 86-2-2SPUX02 ~ Initiate Fast Transfer ESK-8SPU02 Differential to Reserve Station ESK-5NPS13 Protection Relay Transformer ESK-5NPS14 Unit Protection Alt 2 Protective Rela Lockout Rela Action 87-2SPUY02 86-1-2SPUY01 ~ Initiate Turbine Trip ESK-8SPU01 Unit Differential 86-2-2SPUY01 ~ Initiate Fast Transfer ESK-8SPU03 Protection Relay to Reserve Station ESK-5NPS13 Transformer ESK-5NPS14 63-2SPMY01 86-1-2SPUY01 ~ Initiate Turbine Trip ESK-8SPU03 Fault Pressure 86-2-2SPUY01 ~ Initiate Fast Transfer Sh. 2 Transformer to Reserve Station ESK-8SPU03 Transformer Sh. 1 ESK-5NPS13 ESK-5NPS14 Unit Protection Backu Protective Rela Lockout Rela Action 50/51N 86-1-2SPUZ01 ~ Initiate Turbine Trip ESK-8SPU04 2SPMZ01 86-2-2SPUZ01 ~ Initiate Slow Transfer ESK-5NPS13 Protection Relay After 30 Sec. ESK-5NPS14 Block Fast Transfer After 6 Cycles Generator Protection Protective Rela Lockout Rela Action Ref,D~

Gen. Phase OC During 86-1-2SPGZ01 ~ Initiate Turbine Trip ESK-8SPG01 Startup 86-3-2SPGZ01 ~ Initiate Slow Transfer ESK-8SPG04 50-2SPGZ02 After 30 Sec. ESK-5NPS13 Block Fast Transfer ESK-5NPS14

~ This Relay Picks Up Only When Unit is Off Line HSKl

II AXTACEKNT 3 PAGE 3 of 3 Degraded Voltage Switch ear Lockout Rela Action Ref. Dw 2ENS*SWG103 27BA-2ENSB24 No Action Took Place ESK-5ENS18 27BB-2ENSB24 Degraded Voltage Stays ESK-8ENS02 27BC-2ENSB24 During Fault Conditions 2ENS*SWG101 27BA-2ENSA24 No Action Took Place ESK-5ENS14 27BB-2ENSA24 Degraded Voltage Stays ESK-8ENS01 27BC-2ENSA24 During Fault Conditions 2ENS*SWG102 27BA-2ENSC08 No Action Took Place 807E183TY 27BB-2ENSC08 Degraded Voltage Stays Sh 7 27BC-2ENSC08 During Fault Conditions NSK1

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. LAk~ >~~~ Nine Mile Point Nuclear station To Distr OATL 15 August 91 FfLX COal Nine Mile Point Fire protection Program Post Event Xnterviews After interviews conducted today with Fir e Chief Bernie Harvey, and Firemen Fat Brennan and Nark Locurcio, and concurrence with Terry Vermilyea, System Expert Pire Detection and John Pavlicko of Caution Equipment Enc., X have reached the following conclusions.

1 ~ Of the 20 fire panels at Unit 2, 18 maintained a normal power supply o 2a. Two Cire panels LFCP113 and 123 transferred to internal battery backup.'b.

These two panels wb'ile on battery will still function normally as long as the 120 VAC is available in the LPCF, which it was.

There was no interruption or decrease of fire proteotioni detection/suppression at the local fire panels.

Fire Panels 849 and 200/1 being fed from QN did have a power interruption. This would have left the control switches operable at Panel 849, (as they are fed from LPCP), but control Room with no Cire annunciation. Any fire suppression/indication could also have been initiated locally.

ABA: dlc T, Tomlinson A. Julka (FAX 7225 - SN)

D. Pringle

QJQ 15 '91 15' ttt tKT NaÃC Ss ~ DTS

+~AD-+8'~

P.3 g7 INTSHNAL COhllSNKNDRNCK 4 CLopf INN'tMAeSN pg4gy Lo en ~ Nine M5.1e Point Nuclear Station To FiI 15 'August Ql RLR COOI SUSJCCT Nin<<Mile Point, Unit 2 Fire Protection Program Feet Rvent 8/13/91 Interviews

?ire Dept. Personnel Interviews( Poet Iveat of august 13( 1901 Bernie Harvey - Chief ln early fox coverage, interviewed for loss cf power in Contxol Building. Lights blinked, loud noise (louder than ever heard in plant), was in Fire Dept. office( told shift to get out into plant.

Pat Wilson was in Rx Bldg> switched radios to Channel 10, standard Fire Dept. practice if suspect lose of repeator.

Pat Bxennan was in the Foam Room and proceeded to the Chief(s desk.

Chief Harvey heard fire panel alarming when he got to Control Building. Went past Fir~ Panel 114 in Turbine buildf.ng passageway(

no audible alarms( seemed normal.

Mar}c Locurclo went to Panel 12d - 214 elev. while Chief Harvey went to Panel 127>> 244 elev. t these were sounding trouble alarm and D&

normal - no was clear. Went past Panels 120( 121 ( 128 f they were audible.

Pxior to Site Aea Emergency (SAE) message and evacuation being announced - Pat brennan reported Panels R.B. normal, called cn Gaitronics - had to silence Panels 113 on I, B. 250 and than silenced all Fanele in R.Be ( Panels 101, 103( 104( 105( 10d( 10>

and XQ8.

Chier Harvey wae Cofnp to tri~e etage wet ln R h. a.nd have aan in R.s. cnarde Lynn Roon, accocpanled hy Larry cchaner, called hfa supervisor, when they saw transformer blow.

Chief Harvey wou14 have liked tO get to transfcrmer quf.oker for

".ire evaluation.

OV41QLCiOt1 He feels it was at least one hour be for e,'

'nl e

ch'f Harvey feels Fire Dept. should have been part of investigation/inspection team with Operationse

QJQ f5 '9t 15~41 tt% JKT l%WT & CCttl DTS P.4 5'ff'Acp-m~y- g p~r- gg p 1991 1'nterviev (Cont '4) g Pat Pat m inoffice Chief"'s foam Room and approximately 0550>

asked what noise was.

heard loud noise, vent to Lighting dimmed, one string of lights off (NOTE: these feed fram Emergency - UPS should have gone off)

Then he vent on rover - heard alarms - which vere on vater treatment system panel, then vent to Panel 123. There were no displays on DAX panel, vas blank no lights vere on. Power lights vore off. Trouhle Light blinking.

Rent to T.S, 261 NN, eigned sheet, stairtower dark'no problem, knew vay around), Turbine Traok Bay 4imly lighted.

Wont to T.S. 306 - OK, sign>>4 sheet T B Svgr 277 OK) signed sheet T.Q. 250 by Feedpumps - noted not running by Panel 113 - no Lights on, no audible or trouble alarm estimat>>s time approximately 0605 Continued raver rounds to Panel 106 South Stairtover R.S. 249 vas alarming display sai4 "on internal clock" had tvo troubles displayed Went to Q.B. 215 tire panel 103 alarming - silenced R. B. 190 Fir~ panel 101 alarming silenced both panels were in trouble - unknovn R.B. 175 Signed sheet R.B. 261 SBCTS - OX Panel 105 - silenced troubles CQ2 Room, about t?)is time, evacuation alarm sounded went to Unit 2 Control Room assembly point Walked around with Pat Brennan on 8-15-91 ta Panel 123 and Panel 113, power on light vas burned out on Panel 123. "Power on" Light was on, on Panel 113 ~

.AJG 15 '91 15:41 N1 le MGKI Sc COPFl DTS P.5 Aff~Alm8Ng g P08 +opp post I+gt kuy.

C 13, 1991 Xnterview (Cont'4)

Mark ZcNtok,o (Calle4 at home)

Has located in the Fire Dept. Office when lights flickered and noise was heard. Radio communication was gone, Hear Here was out.

Chief Harvey directed personnel to cover vital areas. Pat wilson was in RX Bldg. Pat Brennan was roving T.B. Bernie f Hark were tc cover Control Bldg.

Trip to C.B. uneventful Panels Passed in route)

Panel 114 Elect. Bay Elv.

120 C. 5 Elv. 261

~

261'anel Normal 128 C.5. Elv. 261~

Panel 121 C. B. Elv, 125 C.B. Zlv.

214'ormal 261'anel

'anel Normal Normal Normal 127 C.B. Elv. 261'anel Trouble, Horn sounding-2i4'anel SU,enaod 126 C.B. Elv. Trouble Horn sounding-lilenoed, also an amber light was lit on panel Checked valve room on C.b. elv. 2ii'ight was on in room. No indication of system actuation.

stairwells were dark, Elv, 261'.B. was dark. s.A.E. announcement and reported to Control Room.

I A<7~mgur 7 pt)c,p k~

NMP2 LIGHTING SYSTEM POWER SOURCE AND MINIM)St ILLUHINATIONAVAILABLE - CRIT]CAL AREAS PAGE I MODES OF OPERATION TRANSIENT LOCA St SEISMIC WITH LOOP WITHOUT LOOP MIN. X MIN. X X OF X OF ILLIIL HIN. MIN. ESSENTIAL SIXRCE6 PROVIDED BY POWER AVAIL (FOOT POWER SDUIKES

~~~

BY POWER AVAIL.

<FOOT POWER SIXRCES PROVIDED BY POWER AVAII

)FOOT ~ES POWER PROVIDED (FOOT POWER SOURCES PROVIDED AVAIL.

(FOOT LIGHTING UPS PAtEL SIXRCE CAN)LE) SIXRCE CANDLE)

SOURCE CANDLE)

SOURCE CANDLE)

SOURCE CANDLE) IL CIXITROL ROOH N)RMAL 58 NORMAL NORHAL 58 S NXR BATT. PACK IDPERATING HANXACTIRER-EXIDI AREA 5 RELAY ESSENTIAL )9 (TYPICAL)

ESSENTIAL 18 ESSENTIAL ESSENTIAL ESSENTIAL 18 PANEL AREA) 159 CONTROL BLDL EHE ROE 49 EMERGE 48

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EL. EHERGENC 336'E-65E 8 NXR 8 NXR 8 NXR 8 NXR S NXR BAT.PACK BAT. PACK BAT+ PACK BATo PACK BAT.PACK NONE CONTROL ROON HORHAL 189 N THE LIGHTING MRTM-SOUTH WINGS, CIRCUITS CDRMDORS) TARTING WITH AN 'N ICATE NRMAL POWI CONTROL BLDL WITH A %'H)ICATE EL 3P&'E-&5E ESSENTIAL POWER, WIT)

AN 'E'INDICATE 8 NXR 8 NXR S NXR S NXR S NXR EMERGEN:Y POWER.

BAT.PAtx NONE BAT. PACK BAT. PACK BAT+ PACK BAT.PA)X NRHAL 58 NORHAL 58 NORHAL NORHAL NORMAL 58 2VBB-UPSID CONTROL ROOM (SHIFT SLPERVISOR ESSENTIAL 18 ESSE NTI ESSENTIAL 18 OFFICE) 16 16 CINTROL BLDL PAMPAS)

ELo 3P&'E-65E EMERGENC EHERGE EMERGENC i8 S NXR S NXR S NXR S NXR S NXR BAT.PA)X NONE BAT. PACK BAT+ PACK BAT. PACK BAT. PACK RELAY AND NORHAL 58 NORHAL 2VBB-UPSID CO)4'UTER ROOM RELAY ESSENTIAL 18 ESSENTIAL ESSENTIAL ESSENTIAL 18 CONTROL BLDL EMERGENC 49 EHERGE EMERGENC <9 EL 28F-6'E~

S NXR S NXR S NXR S NXR S NXR BAT+ PACK BAT. PACK BAT. PACK YES BAT. PACK BAT. PACK NORHAL 'Q 2VBB-UPSID RELAY AND COtPUZER CQ4%6EA ESSENTIAL 18 ESSENTIA. ESSENTIAL 18 IKXNO CONTROL BLDG.

EL 288'-6'E-650 S NXR 8 NXR S NXR S NXR 8'NXR BAT PACK BAT. PACK BATe PACK BAT+ PACK YES BAT+ PACK

AtrocmC~r 7 PAcEX,~<<

'MP2 LIGHTING SYSTEM POWER SOURCE AND MINIMUM ILLUMINATIONAVAILABLE PAGE 2 HOOES OF OPERATIDN TRANSIENT LOCA tt SEIS)GC WITH LOOP WITHOUT LOOP

~R It OF ILLLSL MIN. 2 DF ILLLSL 2 OF ILLLSL Hl)L / OF ILLUM MIN. ESSENTIAL PRDVIOED AVAIL. PRLMDED AVAIL POWER AVAIL. POWER AVAIL POWER AVAIL. LIGHTING SOURCES LFOOT LFOOT PROVIDED PROVIDED BY POWER SDLRCES LFOOT SOURCES LFDOT SOURCES LFOOT UPS PANEL SOLSCE CQOLE) BY POWER SOURCE C~E) BY POWER SOURCE CAN)LE) BY POWER SOURCE CANDLE)

BY POWER SOURCE CANDLE) IIL RELAY AN) NORMAL NORHAL 98 2VBB-ASS CQ%'UTER ROOM ESSENTIAL 18 ESSENTIAL LCLXLRIDLRS)

ESSENTIAL 18 CONTROL BLDG.

EL 288'-6'E-65D S NXR S NOLR S NXR S NXR S HOLR BAT. PAIX BAT. PACK BAT. PACK BAT. PACK YES BAT. PACK DIESEL N)RMAL 78 NORHAL 78 NORHAL NORHAL NORMAL 78 2VBB-UPSID GEtKRATOR BUILDING ESSENTIAL 18 ESSENTIAL ESSENTlAL 18 tWORKING AREA) 28

~

EHERGE EME ROE NC EL 261'E-6BC S NXR S NXR S NOLR S NXR S HOLR BAT.PA)X BAT. PACK BAT. PACK YES BAT. PACK BAT. PACK NORHAL 78 NORMAL 78 NORHAL NORHAL NORMAL 78 2VBB-UPSID DIESEL GEtKMOR BLBLDING ESSENTIAL 18 ESSENTIAL 18 ESSENTIAL ESSENTIAL ESSENTIAL 18 LELECTRICAL EQ)IPMENT 38 AREA) EMERGE 28 EMERGENC 28 EHERGENC 28 EL. S NOLR S NXR S NOIR S HOLR S HOLR BAT.PAtx N 261'E-6BC BAT. PACK BAT. PACK BAT, PACK BAT. PACK DIESEL NORHAL 98 NORMAL 98 NORHAL NORMAL NORHAL 98 2VBB"UPSIO GENERATOR BUILDING ESSENTIAL 18 ESSENT)AL 18 ESSENTIAL ESSENTIAL ESSENTIAL 18 LGENERAL AREA)

EL 261'E-68C S NXR BAT.PALX ~ S NXR BAT. PACK S NOLR BAT. PACK YES S NXR BAT. PACK YES S NOtR BAT.PaX

11 HHP2 LIGHTING SYSTEH POWER SOURCE AND HINIHJH ILLUHINATIONAVAILABLE PAGE 3

. HXKS OF OPERATION TRANSIENT LOCA 8 SEISHIC WITH LOOP WITHOUT LOOP 2 OF 2 Hl)L 2 OF ILLUH. HIlL 2 HIN. I OF HIN. ESSENTIAL POWER POWER AVAIL. POWER PROVIDED AVAIL+ POWER PROVIDED AVAIL. POWER PROVIDED AVAIL. LIGHTIW SO(SCES PROVIDED BY POWER (FOOT SOURCES I ROY)GEO BY POWER (FOOT SOURCES BY POWER BY POWER (FOOT CANDLE)

S~ES BY POWER (FOOT CANDLE)

UPS PAtKL IIL REHARKS CA)b)LE) SOURCE CANDLE) SO(SCE SOURCE SOURCE SOURCE NORHAL YES REHOTE SHUT DOWN ROOH CONTROL BLDL 16.5 IL5 EL 261'E-&5C EHERGE YES YES EHERGE EHERGENC YES EHERGENC YES EE-165C 8 8XR 8 HOLR 8 HOLA 8 HOLR 8 dna N BAT. PACK YES BAT. PACK BAT.Pox E BAT. PACK BAT. PACK STANDBY N(RHAL NORHAL NORHAL YES 2VBB-UPSID SWITCHGEAR ROOH a) SWG. PANELS ESSENTIAL ESSENTIAL ESSENTIAL ESSENTIAL YES ESSENTIAL YES (2) HCC FRONTS 35 CONTROL BLDG. EHERGE EHERGE EHERGE YES EHERGENC YES EL 8 261'E-65C 8 BXR 8 HOLR 8 N(XR YES 8 HXR HOLR EE-165C BAT. PACK BAT. PACK BAT. PACK BAT. PACK BAT.PACK NORHAL NORHAL NORHAL NONE NORHAL YES 2VBB-UPSID EPICS SWITCtSEAR RQOH ESSENTIAL ESSENTIAL ESSENTIAL YES ESSENTIAL YES CONTROL BLDG. 15 15 EL 261'E-65C EHERGENC EHERGE EHERGENC YES EHERGENC YES EE-165C 8 BXR a exa 8 (XXR 8 IRLR 8 (K)LH BAT+ PACK BAT. PACK BAT. PACK BAT, PACK BAT.PA(X (CORRIDORS)

NORHAL NORHAL YES 2VBB-UPSID STANDBY SWITCH%EAR ROOH ESSENTIAL ESSENTIAL ESSENTI(V. YES ESSENTIAL YES CONTROL BLDL EL+ 26)'E-65C 8 NXR 8 NQLR 8 HRR 8 NXR 8 N(na NONE EE-16SC BAT. PACK BAT. PACK BAT. PACK BAT.PA(X BAT PACK

NHP2 LIGHTING STSTEH PO)fER SOURCE AND MINIHUH ILL'NfINATIONAVAILABLE PAGE HODES OF OPERATION TRANSIENT LOCA 8 SEISMIC

))ITH LOOP NITHOUT LOOP HIN. HI)L K HIM. '"LU)L ILLlH HIN ILLUH HI)L ESSENTIAL PDVER AVAIL POVER AVAIL Pom PROVIDED AVAIL. POVER PROVIDED AVAIL POVER PROV)DED AVAIL. LIGHT1tO REMARKS SOURCES fF DDT SOURCES fFOOT fFOOT SOURCES fF DOT SOURCES lFOOT UPS PANEL BY POVER SRSCE C~E) BY POVER SOLACE CAtOLO BY POVER Sm)RCE CANDLE)

BY PDVER SOURCE C~E) BT POVER SOURCE CANDLE) ID.

NORHAL 199 NORHAL IBB NORHAL 2VBB-UPS)0 STAHDBT S)fITCHGEAR RDOH ESSENTIAL YES ESSENTIAL YES ESSENTIAL NONE ESSENTIAL YES IEAST CABLE CHASE AREA)

COHTRCL BUXL EL Ãl'E~

EE-)at)c 2VBB-UPSIC NOTE a HOUR COMHON 2VBB-UPS10 BATTERY PACK PROVIDED It4.T OH INSIDE AREAS ISTAIR)fATS) ESSENT IIL I99 ESSENTIAL 198 ESSENTIAL IBB 199 SAFE SHUTOOVH PATHS.

fALL IRI)VDOS) 8 tKXA 8 HOLA 8 )NUR 8 HDtA YES 8 )K)UR BAT.PACK BAT+ PACK BAT+ pAcK BAT+ PACK BAT+ PACK NORHAL YES NORHAL 2YBB-UPSIC HDTE 8 HOUR COHMCN 2VBB-UPSID BATTERY PACK INSIDE AREAS PROV)DEO CN.T OH fEGRESS PAT)a ESSE)fl)AL YES ESSENTIAL YES ESSENTIAL SAFE SHUIDOVN PATHS.

fALL NhtfltCS) 8 talA 8 H)XA a tK)UR YES 8 HOtA YES a tK)UR BAT. PACK BAT. PACK BAT PACK BAT. PACK BAT. PACK 2VBB-UPSIC COtafDN 2VBB-UPSID ESSENTIAL 199 ESSENTIAL tONE ESSENTIAL IBB ESSENTIAL IBB EXIT SIGNS ESSENTIAL 199 OV.L DR IVI)OS)

Af'fnareevV 7 IAAF g NMP2 LIGMTING SYSTEM POWER SOURCE AND MINIH)M ILLUMINATIONAVAILABLE PAGE M(K)ES OF OPERATION TRANSIENT LOCA h SEISMIC WITH LOOP WITHOUT LOOP MIN. / MIH. X ILLUM. Ml)L MIN. 2 ESSENTIAL POWER AVAIL POWER AVAIL. POWER AVAIL. POWER AVAIL. POWER AVA'L- LIGHTING SOURCES (FOOT SOURCES PROVIDED (FOOT Q)URCES PROVIDED (FOOT'ES PROVIDED (FOOT SOURCES PROVIDED (FOOT UPS PANEL BY POWER SOURCE CA)NLE) BY POWER SDLRCE C~E) BY POWER SOURCE CA)K)LE) BY POWER SOURCE CANDLE) BY POWER SOURCE C NXE) ID.

NORMAL NORMAL NORMAL 2VBB-lFSlO STA)4)BY SWITCNGEAR RMM ESSEHTIAL YES ESSEHTIAL ESSEHTIAL ESSEHTIAL YES ESSENTIAL YES (GENERAL AREAS)

(XNTROL BLD(L E(

2GI'E-65C EE-)65C 2VBB-lPSIC CtÃNN 2VBB-UPSID IHSIDE AREAS (STAIRWAYS) ESSENTIAL IBQ ESSENTIAL ESSENTIAL ESSENTIA. 188 ESSENTIAL IBB (ALL DRAWINGS) b NOIR S )K)LR S )K)LR S HOLA S HOLA BAT+ PACK BAT. PACK BAT. PACK BAT PACK BAT PACK NORMAL YES NORMAL HORMAL 2VBB-UPSIC )NTE S HOLR CROCK 2VBB-UPSID BATTERY PACK INSIDE AREAS PROVIDED ONLY ON (EGRESS PATH) ESSENTIAL YES ESSEHTIAL YES ESSENTIAL ESSEHTIAL YES ESSENTIAL YES SAFE SWTOOWN (ALL DRA)O(GS) PATHS.

b HSLR S HOLR S HOLR S HOLR S HGLR BAT, PACK BAT. PACK BAT. PACK YES BATs PACK YES BAT. PACK 2VBB-UPSIC C&tQN 2VBB-IfSIO IHSIDE AREAS EKIT SIGNS ESSENTIAL IBB ESSENTIAL ESSEHTIAL ESSENTIAL IBB ESSENTIAL IBB (ALL Df(AWINGS)

l'll ATf4~6nlT' P~~ gong ISIP2 LIGHTING SYSTEM POWER SPLRCE AND MINIINM ILLUMINATIONAVAILABLE PAGE 5 MOPES OF OPERATION TRANSIENT LOCA dc SEISMIC WITH LOOP WITHOUT LOOP ILLLH. MIN. MIN. MIN. /

ILLLSL MIN. ESSENTIAL AVAIL POWER AVAIL. POWER AVAIL. POWER AVAILe POWER AVAIL. LIGHTING SDLRCES PROVIDED BY POWER SXRCE LFppT CA)6)LE)

SOURCES PROVIDED BY POWER SOURCE LFOOT CANDLE)

SDLRCE $ BY POWER SOURCE LFOOT CAINLE)

SDLRCES pROVIDED BY POWER SOURCE (FOOT CANDLE)

SOURCES BY ~R SOURCE (FOOT CANDLE)

UPS PAHEL 10 CLXITRPL RXN M)R)LAL 2VBB-L$%$

LEAST-WEST CORRIDON ESSENTIAL 33@ ESSENTIAL NONE ESSENTIAL ESSENTIAL 333 CONTROL BLDG EL. 386 EE-65E b HXR S HXR $ HXR S HXR S NXR BAT. PACK BAT. PACK BAT. PACK BAT PACK BAT. PACK VBB-iX%10 Q)RTfKAST STAIRS ESSENTIAL CONTROL BLDG. ESSENTIAL 198 ESSENTIAL 189 NONE ESSENTIAL EE-65E EE-650 EE-165C EE~ S WXR S BXR $ HXR b HOLR S HNR BATo PACK BAT. PACK BAT. PACK BAT. PACK BAT. PACK SOUTHWEST 2VBB-UPS10 STAIRS CMfRPL BLDG ESSDITIAL 189 ESSENTIAL 188 ESSENTIAL NONE ESSENTIAL 189 EE-66B EE-650 EE-66F EE-65C S IXXR S HOLR S HOLA S HOLR S HOLR EE-165C 'YES BAT. PACK BAT. PACK BAT. PACK BAT. PACK BAT. PACK YES NORHAL YES NORMAL 2VBB-UPS10 INTER BAY RA)4 ESSE NTIN. YES ESSENTIAL YES ESSENTIAL NONE ESSENTIAL ESSENTIAL EL 258 Tp EL 261 EE-7% S IKXR S HXR S INLR b NXR S HOLR BATo PACK BAT+ PACK SAT PACK BAT+ PACK BATs PACK

1

%%>2 I.IGHTING SYStEH POwER SOURCE ANO HINI)K)H ILLUHINAtlONAVAILABLE PAGE 6 HOOES OF OPERATION TRANSIENT LQC4 LOCA 5 SEISHIC WITH LQIP WITHOUT LOOP X IF X OF X

~R ILL)M.

PROVIDED Ht)L 4VAIL ILLU)L PRQVIOEO AV41 POWER HIN.

4V4IL POWER tu~

PROV IOEO FOOT'V4IL, PQWER

% OF ILLIH.

PROV IOEO HIN.

4VAIL ESSENtIAL L[GHTINO BY POWER SOURCE

)FOOT CANOLE)

BY POWER SQRCE

<FOOT CANOLE)

SOURCES BY POWER SOURCE

<FOOT SQRCES BY POWER SQRCE ~E) BY POWER SOURCE (FOOT CANIXE)

UPS PANE) 10.

NQRHAI. YES NQRHAL NQRH41. YES ZVBB~IO REACTIR IXOO.

EL 353'-N'EET SSENTIAL YES 'ftAL YES N)'IAL ESSENTIAL YES SSEN TIAL YES J

8 HOIR 8 NXR 8 HOUR 8 HQR YES 8 HQR BAT PACK BAT. PACK BAT PACK BAT PACK BAT PACK NORHAL YES NORHAL NQRHAL NORHAL YES ZYBB~IC REACTOR KOG.

AUX 84YS NQ)TH SSENTIAL YES NTIAL YES SSENTIAL ESSENTIAL YES SSENTIAL YES EL 215'~

EE&TL 8 NXR 8 HOUR 8 HOUR 8 HQR YES 8 HQR BAT. PACK BAT. PACK BAT. PACK BAT. PACK BAT. PACK REACfOR M)O.

NQRHAL YES NORHAI NORMAL NORHAI YES ZVBB~IO AUX BAYS SQ))H TIAL YES 'IIAL YES ENT IAL SEN'flAL YES SSENTIAL YES EL 2)5'448'-

EE&7L 8 HQ)R 8 NOIR 8 HQ)R YES 8 HQR YES 8 NQR BAT. PACK BAT. PAOC BAT. PACK BA'f. PACK BAT. PACK NQRHAL YES NQRHAL YES NOR MAL NQRHAL NORHAL YES ZVBB~IO AUX SERVICE BLOG. SOUTH EL 261'E&7P SSENTIAL YES TIAL YES SENrtAL YES SSEN)'IAL YES 8 NXR 8 NXR 8 HQR 8 HQR 8 HQR ltAT PACK BAT. PACK BAT. PACK 84T. PACK YES BAT. PACK HORHAL YES NQRHAL YES 2VBB-UPSIC SCREENWEIL SLOG.

EL 261'E-728 SSENTW. YES TIAL YES fIAL SENT IAL YES SSEN'ftA). YES

~

8 )KXR 8 HQR 8 HOUR

'YES 8 NXR YES 8 HQR BAT. PACK BAT. PACK BAY.) AC 84T. PACK BAT PACK LGHTIl4 IN REACTOR BUILOING IS POWEREO FR(H PLANT EHERGENCT POWER OISTRIBUTIQI STSTEH. OURING LOC4, 'fHIS NQI-IE LIGHttNG SYSTEH POwER IS TRIPPEO BY AN ACCIENt SIGNAL

J8%'2 LIGHTING SYSTEM POVER SOURCE ANO MINI %H tLLUHINAI'ION AVAILABLE PAGE 7 HQQES QF 6%JIATION TRANS IEN T LOCA 8 SEISHIC 'VITH LOOP VITHIXJT LOOP 8 OF 8 OF HIIL 7 OF HIIL TLLI84. HIM.

AVAIL HIJL AVA~ POVER ILL~ AVAIL POVER ILLUH. HBL AV40 POVER AVAIL.

ESSENTIAL LIGHTING PRQVIOEQ PROV!OED REMARKS SIXRCES BT neCR IFOOT BY POVER IFOOT SmRCES BY POVER (FOOT SIXRCES BY POVER BY POVER IFOOT UPS PAWL SCXJRCE CAHJLEJ MIRCE SOURCE SOURCE CANm.E) SOURCE CANQLEI IL TIR BLDG.

HJRHAL YES NORHAL Nt& NORHAI. NORHAL YFS 2VBB~IC Et 2I5 EEOC S%NTIAL YES SSEMTIAL 'IES SSEMTIAL ESSENTIAL ESSEM'f IAL YES SPENT RKL 8 NXR 8 HXR YES 8 HXR YES 8 NXR YES 8 NOIR CQm.DKI BAT, PACK BAT, PACK BAT, PACK BAT, PACK BAT. PACK AREA NORMAL YES NORHAL YES HOKED VBB~SIC TOR BLDG.

EL. 2<8 M %7ITIAL YES ESSENTIAL YES SSEMTIM. YES SSEMTIAL TES EE+7D 8 HXJR 8 HXIR 8 NXR YES 8 NXR YES 8 HXR YES

, BAT. PAI7( BAT, PACK BAT, PACK BAT, PACK BAT. PACK NORHAL YES NORHAL HORHAL HJRHAL YES 2VBB~SIC ACCESS P4TH t74.Y NO%'TIAL SIJITIAL YES 'YES SSEMTIAL YES SSDITIAL YES 8 HXJR 8 HXR 8 NXR 8 NXR YES 8 MmR BATe PACK BAT, PACK YES BAT PACK YES BAT, PACK BAT, PACK QRHAL YES MORHAL HJRHAL YES 2VBB-ITIC SDITIAL YES YES SSEMTIM. YES $ %MTIAL YES 8 HXR 8 HXR YES 8 NXR YES 8 NXR YES 8 IKXR BAT, PACK BAT. I ACK BAT, PACK BAT PACK BAT, PACK WeeL YES NDIHAL NORMAL YES 2VBB-IPSIQ TOR BLQd.

SEJITIAL YES ESSOITI YES SSEMTW. ESSENTIAL YES SSBITIAL 'YES Et 328'-l8'%7M 8 HXR 8 HXR YES 8 HXR YES 8 NOIR YES 8 NXR Bar. I ACX BAT. PACK BAT. PACK BAT. PACK BAT. PACK i NIXBIAL LIGHTING IM REACTOR BUILDING IS POVERED FROM PLANT EHERGEMCY PQVER OISTRIIXJTION SYSTEH. OIRIMG LOCA, THIS NON-IE LIGHTII4) SYSTEH PQVER IS TRIPPEO BZ AN ACCIDEMI'IGNAL~

avTmH>~f 7 pres g'+

%(PZ LIGHTING SYSTEH POwER SOURCE ANO HINIHUH ILLUHINATIQNAVAILABLE PAGE 8 HOOES OF OPERATION TRANSIENT LOCA 8 SEISMIC WITH LRP WITHOUT LOQP HIN. ILL~ HIM. I LUH HIN, ILLUH. HIN. ILLUIL HIN. ESSENTtAL

(~T ~ER 4V4ll 4"4'"-

POWER PROV IOED BY PQWER (FOOT C(WE)LE)

POWER SOURCES BY POWER AvAIL.

(FOOT POWER SOURCES PROVIOEO 8'I POWER

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(FOOT POWER SOURCES PROvtOEO Y POWER AVAIL C~E)

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REHARKS S(X)RCE S(mRCE SOURCE SOURCE SQLIICE ACT6I BLOC. ZVBB ~LB ST4IRS EE-67E EE-67F SDITIAL IBB SENT IAL 188 te8 E'E-67O EE%7H EEWTJ 8 )CUR 8 HOUR YESi 8 IXXXI 8 IKXXI 8 H(XXI BAT, PACK BAT, PACK BAT, PACK BAT PACK BATe PACK T& BLOC. ZVBB~LC AUX. BAYS N(XITH TIAL IBB SENTIA(. SSENTI4L ST4IRS EE<7L 8 HER 8 Ie)R YES0 8 IKNXI 8 IXXXI 8 H(X)R BAT, PACK 9AT. PAO( BAT, PACK BAT PACK BAT, PACK ACTUI BLOG. ZVBB-UPSLO AUX. BAYS SOUTH ST4IRS SENT IAL IBB ESSENTIAL IBB EE.67L 8 IOLXI 8 HOUR YES' IKWXI YES 8 IKX)R 8 IKXXI 84T, PACK BAT+ PAO( BAT PACK BAT, PACK BAT+ PACK HORHAL LIGHTING IN REACTOR BUILOING IS POWERED FROM PLANT EHERGENCY POWER DISTRIBUTION SYSTEH. IXNING LOCA. THIS NON-IE LIGHTING SYSTEH POVER IS TRIPPEO BY AH ACCIDENT SIGNAL.

NMP2 LIGHTING SYSTEH POWER SOURCE AND MIHINJM ILLUMINATIONAVAILABLE PAGE MODES OF DPERATIDN TRANSIENT LOCA 4 SEISHIC WITH LOOP WITHOUT LOOP X

ILLLÃ. MIN. I ILL MIH. OF X OF ESSENTIAL POWER PROVIDED AVAIL. POWER AVAIL. POWER AVAIL. POWER POWER ILLU)L AVAIL. LIGHTING SOURCES PROVIDED PROVIOEO pRovloEo BY POWER (FOOT SOURCES IFOOT SOURCES IFOOT SOURCES (FOOT SOURCES (FOOT O'S PANEL BY POWER SOLRCE CA)K)LE)

SDLRCE CANDLE)

BY POWER SOURCE C~E) BY POWER SOURCE C~E) BY POWER SOURCE C~E) ID.

TLRB. BLDG. NORMAL YES HORMAL NONE NORMAL YES 2VBB-LPS1D SAFE S)IJTDOWN GRMM) FLOOR PATH O)l.Y No CORfODOR ELXJIPPKNT ELe ESSEHTIAL ESSEHTIAL YES ESSENTIAL NONE ESSENTIAL YES ESSENTIAL YES 258'E-66B 8 NXR 8 HLXR 8 HOLA 8 NXR 8 HOLR BAT+ PACK BAT+ PACK BATs PACK YES BAT+ PACK YES BATe PACK TURL BLDL NORMAL NORMAL YES NORHAL NONE NORMAL NORMAL YES 2VBB-UPSIO SAFE SHUTDOWN CLEAN ACCESS AREA 2VBB-UPSIC PATH D)LY NO ESSENTIAL EOUIPMENT EL. 2QY ESSENTIAL YES ESSENTIAL NONE ESSENTIAL ESSENTIAL YES EL 2Q'L.

288'-8'L.

396'E-66H 8 )KXR 8 HL)LR S HXR S )NLR S HOLR BAT. PACK BAT. PACK BAT PACK YES BAT. PACK YES BAT. PACK TtSL BLOL 2VBB-UPSIC SAFE SWTDOWN CLEAN ACCESS PATH M.Y ND AREA EIXJIPPKNT STAIRS ESSEHTI)V. YES ESSENTIAL NONE ESSENTIAL YES EL+ 258'L 2Q'L 288'-8'L 386'E-66H b HOLR 8 HOLR 8 HXR S HOLR 8 HOLR BATo PACK BAT. PACK BAT PACK BATo PACK BAT. PACK

IU ACCESS ROUTE TAKEN BY OPERATOR FROM CONTROL ROOM TO UPS ROOM IN NORMAL SWITCHGEAR BUILDING ON 8-13-91 The following route was taken by operator from control room to go to UPS room in switchgear building to transfer alternate power source to UPS units

,Operator left the control room EL 306 through south door and proceeded to west. Then he turned north along the corridor on the westside of the control room. Then he exited the control room building through north west door EL 306 to Auxiliary building. He then took the stairway just south of the elevator to go to EL 261. Then and at EL 261 of Auxiliary building, he proceeded to south entered the corridor ( Electrical equipment Tunnel). From the corridor he entered the normal switchgear building EL 261 and proceeded to stairway located in the center of the building (West half) down to EL 237 where the UPS units 2VBB-UPS1A, 1B, 1C and 1D are located. He then transferred the UPS power to maintenance power source.

After restoring power to the above UPS units, the operator proceeded to UPS 2VBB-UPS1G via the door on the east end of the room, went south down the hall, through the door on his left (eastside) and entered the control building. He then took the stairs down to EL 214 where UPS 2VBB-UPS1G is located and transferred the power to the maintenance power.

CONDENSATE/FEEOMATER SIMPLIFIED SKETCH FEEOvATER COMlROL LOO)C I ) I I I

) I I I PRESS)I)RED lCQOCM JEANS LVIB REAC)TX)

FEll4 FL VESSEL I O'RVI I I I I I I I QlZEMSATE I BOOSTER I I FVg I I I I I i FVRi ) FOI)MFlO PAWL C(ÃH6ATE PAP HIM. FLOM IEgKR ICQI+QN COMPENSATE )MISTER PNTP HDL FLOM TEAOER FEEOPUH'lM. FLOV TRACER FOXBORO PANEL TYPICAL TRAIN A, 8,8, C TRAIN A - 2CEC-PNL825 CROSSOVER HEADERS BETWEEN TRAINS TRAIN B - 2CEC-PNL826 (PROVIDE CROSSOVER FLOW TRAIN C - 2CEC-PNL827 FEEDWATER CONTROL PANEL 2CEC-PNL6I2

Oe A, T rAQf tttl +II '/

fPRO Pomr Generation Services Department General Electric Company Q

GE Industrial a power Systems 3532 James St.. PO. Bott 484t, Syraorse. Ny t322t NIAGARA MOHAWK POWER CORPORATION cc: NIAGARA MOHAWK POWER CORP.

NINE MILE POINT NUCLEAR STATION UNIT g2r GENERATOR g180X632 R. Abbott GENERATOR INSPECTION POSSIBLE N. Kabarwal PHASE-TO-PHASE FAULT M. McCormick GENERAL ELECTRIC COMPANY L. Jordan (37-3)

August 28, 1991 W. Judd S. Kolb R. Smith W. Turk Mr. Anil K. Julka NIAGARA MOHAWK POWER CORPORATION 301 Plainfield Road North Syracuse, New York 13212

Dear Mr. Julka:

Due to the August 13, 1991 failure of the phase B step-up transformer on Nine Mile Point Unit g2, General Electric Generator Engineering recommends performing a thorough visual inspection of the generator stator end winding support system at the next convenient opportunity.

The inspection should include all accessible components of the stator end winding support system, including stator bar end arms, blocks, ties nose rings, and outer axial supports. This inspection should be accomplished by a GE Generator Specialist trained to detect the potentially subtle indications of damage.

The above recommendation is based upon the possibility of phase-to-phase generator short circuit currents through the failed transformer as high as 5pu. The initial recommendation for the immediate generator inspection considered the possibility of higher currents, resulting in several times greater end winding forces.

Physical evidence of high current forces at the transformer .low side was the primary driver for this recommendation, since measurements of generator currents were not available. Our engineers continued to review the limited data available and subsequently concluded that currents high enough to do probable damage to the generator were not likely. This conclusion was reached primarily by considering a measurement of depressed generator voltage during the incident, inferring generator currents, and specific capabilities of the generator design.

'k Page II Mr., Anil K. Julka August 28, 1991 Should you have any questions regarding this recommendation, please contact me.

Very ruly yours J eph . Kir ch Ma ager Engine ring Services Pow r Generatio Services "SYRACUSE OFFICE JAK/bs JAK-059

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