ML18018B117
| ML18018B117 | |
| Person / Time | |
|---|---|
| Site: | Nine Mile Point  |
| Issue date: | 09/04/1991 |
| From: | Niagara Mohawk Power Corp |
| To: | Office of Nuclear Reactor Regulation |
| References | |
| Download: ML18018B117 (62) | |
Text
'
NIAGARAMOHAWKPOWER CORPORATION NINE MILE POINT UNIT 2 NUCLEAR STATION NRC UPS MEETING SEPTEMBER 4, 1991
OPENING REIVIARKS/PURPOSE B. R. Sylvia UPS OVERVIEW R. J. Crandall ROOT CAUSE OF UPS FAILURE J. T. Conway UPS LOAD EVALUATION A. K. Julka/
R. B. Abbott CLOSING REMARKS B. R. Sylvia
UPS OVERVIEW
UPS - FUNCTIONS 3 - PHASE INPUT CHARGER SECTION - AC to DC INVERTER SECTION - DC to AC STATION BATTERIES LOSS OF NORMALAC TRIPS - t0 (INVERTER ONLY)
Page 4
UPS FUNCTIONS (CONT'D}
IVIAINTENANCESUPPLY (3-Phase)
TRANSFERS IVIANUAL AUTOMATIC INVERTER TO IVIAINTENANCEMONITOR Page 5
NINE MILE P INT UNIT 2 UNINTERRUPTIBLE POWER SUPPLY TYPICAL SERIES (IA, IB, IC, ID, IG)
STORAGE BATTERY l25VDC BATTERY DISCONNECT CIRCUIT BREAKER CB2 INVERTER OUTPUT CIRCUIT BREAKER CB3 DC,TO AC INVERTER I
CB}
1NPUT I
-PHASE VOLTS AC I
I I
I I
I
+28V oo
=2V LP-~ GND AlX~
Sj
= 2 V
-28V POWER SUPPLY UPS I
I I
I I
DC INPUT BREAKER CONVERTER MAINT.
SUPPLY CIRCUIT REAKER CB4 I
I STATIC SVITCH I
I I
I I
I AC OUTPUT TO CRITICAL LOAD 288-128V 3-PHASE 688V 3-PHASE TRANSFORMER 288-128V 3-PHASE REGULATOR 288-128 V 3-PHASE MAINTENANCE SUPPLY
TRIP ALARMS INDICATOR LIGHTS 1)
DC Undervoltage (DCUV)
Breaker Trip 2)
DC Overvoltage (DCOV) 3)
Inverter Leg Fuse Blown 4)
AC Undervoltage (ACUV) 5)
AC Overvoltage (ACOV) 6)
Frequency Failure 7)
Logic Failure 8)
Clock Failed 9)
Logic Power Supply Failure 10)
Overload (10 minute delay)
Logic Alarm Module Trip Page 6
0
LOGIC POWER EXIDE -
UPS1A UPS1B UPS1C UPS1D UPS1G B-PHASE MAINT. DC ELGAR - UPS2A UPS2B DC to DC ELGAR - UPS3A UPS3B DC to DC EXIDE -
NINE MILE INT UNIT 2 UNINTERRUPTIBLE POWER SUPPLY TYPICAL SERIES (IA, 1B, 1C, 10, IG)
STORAGE BATTERY I25VOC I
I I
I UPS ICIRCUIT AC TO DC I~PUT IBREAKER CONVERTER I
- INPUT
-PHASE VOLTS AC I
I OC TO AC INVERTER INVERTER OUTPUT CIRCUIT BREAKER CB3 I
I I
I COMPARE BATTERY DISCONNECT CIRCUIT BREAKER CB2 MAINT.
SUPPLY CIRCUIT BREAKER CBn I
I STATIC I SMITCH I I
I I
I I
AC OUTPUT TO CRITICAL LOAD 288-128 V 3-PHASE 688V 3-PHASE TRANSFORMER 288-128V 3-PHASE REGULATOR 288-128V 3-PHASE MAINTENANCE SUPPLY
UPS PREVENTIVE MAINTENANCE SHIFT ROUNDS FILTERS CLEANING SCR HEAT SINK GREASE ZERO CROSSING, SETPOINTS LOADS TRENDED AMBIENTTEMPERATURE (32-104 F)
ROOM TEMPERATURE 93-97 F MAX (WITHOUT HVAC)
Page 8
UPS PREVENTIVE MAINTENANCE
{CONT'0)
~
DEVIATION/EVENTREPORT (4/3/91)
BATTERIES NOT RELIABILITY INDICATION WEIGH PERSONNEL RISK VS BENEFIT Page 9
2.3 tNVERTER The rectiffer/charger or battery OC output is the inverter input power.
This OC voltage is filtered by shunt capacitors contained in OC capacitor assemblies.
The quantity of capacitor assemblies required varies with the KM rating of the UPS nadule, as listed here:
KW ~t~niW 30 60
- 100, 180 250 330 400,'50 Ca acitor Assemblies A15 A15, A16 A15 A15, A16 A15, A16, A17 A15, A16, A17 A18 OC is converted to AC by SCR switching action of the fnverter~egs,'Al, etc.
Each adjacent pair of legs (i.e.,
A1 and A2, etc.) constitutes a bridge circuit which supplies quasi-square-wave AC to one of the primary windings of the power transformers, Tl or T2.
The 30 and 60 KM modules have only one power trans-former, T1.
Component desfgnators for 300 KM and larger inverters are preceded by the numeral 2; e.g., 2T2.. Refer to Figure 2-2.
Secondary wfndings of T1 and T2 are connected so that the resultant output is a balanced 3-phase voltage.
Each line-to-line and lfne-to-neutral voltage wouId
- appear-as a near sfne wave consisting of 12 steps.
This'wave form is filtered to provfde a good sine wave at the output termfnals by the filtering action of AC output filters, A21 (ff used, A22 through A24), and by reactors, L3 through l.8, connected between adjacent pafrs of.fnverter legs.
The fnverter senses fts output voltage'nd regulates within 1% tolerance for a wide varfatfon fn load and OC input voltage.
Various other sensing circuits provide protectfon alarm indications.
See Tables 2-1 and 2-2 for alarm descrf ptfons.
A redundant logic supply, powered by the fnverter output, a separate 120 VAC
'bypass
- source, and/or internal rechargeable sealed batteries.
allows logic testing with no input power applied and keeps alarms indicating for as long as any source of AC control power fs avaflable.
A static faterrupter fs part of the fnverter sensing circuits.
Whenever an UPS module trfpl~ ft met be disconnected automatically and famedfately from the critic& Toad bus.
Not providing immediate disconnection could result fn out-of-tolerance-dfsturbance of the-senA{w critical load.
The UPS module provides fnsCantaneous output isolation vfa internal logic responding to any one of a number of control or protection signals that programs off" all of the fnverter legs.
This produces a force-conautated interruption of the fnverter output, assuming power aetfnufg at the load.
The follerfng fs a lfst of ~or fnverter caeponents and brief description of their functions.
2-5
b.
A primary function fs the storage, via R-S flip-flops, of most alarms and all trip functions ana one display oi miasma c--
on. card-amounted LEDs.
2.3.2. 10 Static Switch Control A13A34.
Thfs control determines the condfCfon of the inverter, bypass
- source, and crftfcal load.
It Chen logically determines whether or not the critical load should be transferred to the bypass source.
It also determines whether the UPS can or should be restarted depending on the UPS condition and the critical load bus.
2.3.3 Control Panel A14 This panel contains control and status display components for the entire UPS mod&-.
See Figure 2-3 5 Table 2-3 for location and description of each.
2.3.4 OC Capacitor Module, A15 (some modules up to Al8, see paragraph 2.3)
Eachslide-fn module contains DC filter capacitors that are fused in groups of seven capacitors.
2.3.5 AC Out ut Filter Panel A21 These Ac capacitors are connected in delta across the fnverter output to filter output waveform.
The capacitors have integral interrupt overcurrent protect-ion.
2.3.6 Load Dfvfsfon and Interface Panel A26.
This panel provides interface between the card cage, A13, and the following:
a.
Load-dtvfsfon current transformer loop (contains burden resistors and loop-shorting relays.
b.
Coamutatfon-1fmft current transformers '(contains burden resistors).
c.
?nverter voltage sensing (potential transformers, 3-phase).
d.
.Signal synchronfzfng node (aeunts sync node transformer).
e.
Slown leg fuse sensing (contains optocoupled electrical blown fuse sensing).
2.3.7 Lo fc Power and Rel Pane)
A27.
Thfs panel contafns posftfve and negative 20 VOC power.supplfes
{PS1 and PS2).
These power supplies are powered through relay A27K1, which selects fnverter output (preferred) or bypass (alternate) source.
Pos)tf ve and negative 18-V sealed batteries (A278T1-BT6) are counted on this panel
'and are kept charged by Che power supplies.
Cfrcuft breaker A27C81 dfsconnects the battery from 2-10
...<<~>>i z~er
~us dn4 lOglc pUwcr supply swizcn N27Sl disconnects tne power supply's 120 VAC input pcwer.
The panel also contains card-mounted (A27A1) t lays which interface the A13 controls with external items such as circuit breaker motor operators, shunt trip coils, and remote monitor panel functfons.
Control battery discharge sens1ng is located on the A27A1 card.
(These batteries should be replaced at 4-year intervals.)
2.3.8 S stem Terminal Board Panel A30.
Th1s panel contains terminal boards for all external control connections.
2.3.9 Remote Alarm A30A1.
The remote alarm panel provides indications of the UPS module status and has no control funct1on, Alarms initiated by the UPS module are as follows:
a.
TRANSFERREO TO BYPASS b.
BATTERY OISCHARGE c.
UPS MINOR ALARM d.
UPS MAJOR ALARM e.
OC UNOERVOLTAGE WARNING.
Ory contact relay closure fnd1cates alarm condition.
Contact rating 1s 10 VA max.,
100 V max., 0.1 A max., reshstive.
2.3.10 Statfc Swftch Le A33.
The static switch leg contains static switch power SCRs, SCR gate drivers, and overtemperature sensing cfrcu1ts.
The stat1c switch leg provides an unfnterrupted transfer of critical load between the fnverter source and the utf1 fty bypass source.
2.3.11 Statf c Swftch Control Panel A34.
This control panel senses crftfcal load and bypass source busses for feeding static switch control card A13A34.
Power supplies PS1 and PS2) produce positive and negatfve 20 VOC for statfc switch.leg (A33) and remote monitor.
2.3.12 AC Fflter Reactor LZ-L8.
Each reactor fflters the AC output of each fnverter leg to power transforaer T1 (and T2 when used).
2.3.13 AC Out ut Fflter Karmonf c Reactors Lg throu L11.
These reactors (fn combfnatfon with A21) fflter the output waveform.
2-11
SECTION 3
MAINTENANCE AND TROU8LESHOOTING
- 3. 1 PREVENTIVE MAINTENANCE.
- 3. 1. 1 General.
A record log should be kept which should include periodic meter readings, maintenance, and any alarms and subsequent actions taken.
Early recognitior of deteriorating performance is important DANGER HIGH VOLTAGE ONLY QUALIFIED PERSONNEL SHOULD ATTEMPT TO.SERVICE THIS EQUIPMENT.
IF INJURY DOES
- OCCUR, APPLY STANDARD TREATMENT FOR ELECTRICAL SHOCK.
3.1.2 Air Filters.
The air Alters should be changed every 2 months(even more frequently if they are dirty).
The filters are comercially available.
Filters may be safely replaced while the UPS is operating and without opening the doors.
Front filters (if so equipped) are accessible by loosening the two screws at the top corners of the hinged filter housing.
The retainer chain allows the filter housing to tilt forward approximately 15 cm (6 inches)
. for efilter removal.
Sottom filters are accessible by loosening the wing bolts (two per filter) located on the front channel below the cabinet access doors.
Mhen the bolts are loosened (approximately 1e5 cm (4 inch), it may be necessary to reach under and pull the hinged filter door down from the front (there are three magnetic clasps).
The filter can now be easily replaced.
3.1.3 Lamp Test.
A lamp test may be perfornad with UPS operating.
3.1e4 Ph steal Ins ction.
It is rec~nded that the UPS be inspected annually for tightness of connections and for evidence of component damage or overheating.
ROOT CAUSE FAILURE OF UPS Page 10
ROOT CAUSE INVESTIGATION COIVIIVION MODE FOR EXIDE UNITS ASSOCIATION WITH TRANSFORMER FAULT INITIALINSPECTION INDICATED LOGIC TRIPPED WITH SOME ALARIVILIGHT ANOMALIES INITIALINSPECTION INDICATED IVIAINTENANCE SUPPLY BREAKERS OPEN 3 POTENTIAL CAUSES EVALUATED 1.
Voltage Transient on Normal AC Distribution System 2.
Propagation of High Frequency Noise From Transformer Fault 3.
Voltage Transient On Station Ground System Page 11
PROPAGATION OF HIGH FREQUENCY NOISE UNLIKELYDUE TO PREOPERATIONAL RADIO FREQUENCY TESTING RADIO FREQUENCY ATTENUATIONTHROUGH STATION TRANSFORMERS LABORATORYTESTING TO DATE Page 12
VOLTAGE TRANSIENT ON STATION GROUND SYSTEM UNLIKELYDUE TO COMMON BEHAVIOR OF ALL 6 EXIDE UNITS BEHAVIOR OF OTHER STATION EQUIPMENT LABORATORYDESTRUCTIVE TESTING Page 13
VOLTAGE TRANSIENT ON NORMAL AC DISTRIBUTION MAGNITUDE OF TRANSIENT IS WELL UNDERSTOOD COMMON TO ALL FIYE UNITS TRANSFORMER FAULT ON B PHASE B PHASE SUPPLY TO UPS LOGIC MAINTENANCE TRANSFER PREVENTED Page 14
IN PLANT TROUBLESHOOTING RESULTS LOGIC TRIPS AT 17 VDC CORRESPONDING TO 85 VAC LOGIC SUPPLY TRANSFER AT 45 VAC LOGIC BACKUP BATTERIES WERE DEGRADED AC SUPPLY TRANSIENTS (100 - 200 IVlSEC) TRIP UNITS WITH DEGRADED BATTERIES AC SUPPLY ~Ling DOES NOT TRIP UNITS LOGIC BATTERY IMPACT Page 15
LABORATORY TESTING RESULTS LOGIC BATTERY FAILURE GROUND VOLTAGE TRANSIENTS EXTENSIVE LOGIC BOARD TESTING NO COMMON MODE FAILURES IDENTIFIED Page 16
CONCLUSIONS IMPROPER LOGIC POWER SUPPLY DESIGN MAINTENANCE SUPPLY VS.
INVERTER OUTPUT LOGIC SUPPLY SWITCHING CIRCUIT LOGIC BATTERY INSTALLATION TRANSFORMER FAULT CAUSED MAINT. SUPPLY VOLTAGE TRANSIENT UPS LOADS DEENERGIZED DUE TO TRIP OF ALL FIVE UNITS TRANSFER TO MAINT. PREVENTED (BY DESIGN)
CAUSE OF UPS TRIPS DETERMINED TO BE MAINT. SUPPLY VOLTAGE TRANSIENT AND SWITCHING CIRCUIT CHARACTERISTIC AND DEGRADED BATTERY CONDITION Page 17
CONCLUSIONS (CONT'D)
VENDOR MANUAL IS DEFICIENT PREVENTATIVE MAINT. SECTION NEGLECTS BATTERIES FOUR YEAR REPLACEMENT FREQUENCY STATEMENT FUNCTION OF BATTERIES NOT CLEAR Page 18
CORRECTIYE ACTIONS PRIOR TO RESTART MODIFY UPS LOGIC POWER SUPPLY TO MAKE INVERTER OUTPUT PRIMARY, MAINT. SUPPLY BACKUP (COMPLETE)
REPLACE ALL LOGIC BATTERIES AND DETERMINE APPROPRIATE SERVICE LIFE/REPLACEMENT SCHEDULE (COMPLETE)
POST RESTART EVALUATE FURTHER MODIFICATIONS FOR o
IMPROVED ACCESS TO BATTERIES o
SWITCHING CIRCUIT CHARACTERISTICS ALARM LIGHT ANOMALIES Page 19
UPS LOAD EVALUATION Page 20
1'(
UPS LOADS PLANTIMPACT 2VBB-UP 1A FEEDWATER, CONDENSATE, COND. BOOSTER, HEATER DRAINS MINIMUMFLOW VALVESFAILOPEN A & C TRAINS FEED PUMPS TRIP DUE TO LOW NPSH PLANTSCRAM (LOW REACTOR LEVEL)
TURBINECONTROL/
REHEATER LOADCONTROL TURBINETRIP REACTOR RECIRC FLOW CONTROL (VALVESA & B FAILLOCKED)
ROD POSITION INFORMATIONCABINET LOSS OF CONTROL ROD POSITION INDICATION ROD WITHDRAWAL INHIBIT ANNUNCIATORPOWER SUPPLY PARTIALLOSS OF CONTROL ROOM ANNUNCIATORS MAYCAUSE LOSS OF ALL CONTROL ROOM ANNUNCIATORSWHEN ALTERNATEUPS ATTEMPTS TO PICK UP ADDITIONALLOADS IF ALLPOWER SUPPLIES ARE FULLYLOADED LOSS OF LWS COMPUTER SYSTEM (LWS, ERF, SPDS)
PARTIALLOSS OF RADIAXBASE AND COMMUNICATION ANTENNA TURBINEBUILDINGCLOSED LOOP COOLING MAXIMUMCOOLING PORTIONS OF DRYWELL UNITCOOLERS
UPS LOADS PLANTIMPACT 2VBB-UPS18 FEEDWATER CONTROL (VALVESFAILLOCKED)
REACTOR RECIRC FLOW
.CONTROL (VALVESA & B LOCKUP)
RECIRC PUMP DOWNSHIFT COMBINATIONOF THE ABOVECAUSES HIGH LEVELTURBINETRIP LOSS OF PORTIONS OF DRYWELLUNIT COOLERS ROD SEQUENCE CONTROL SYSTEM FULLCORE DISPLAYINOP (ROD POSITION AVAILABLE FROM 3D-MONICORE AND PMS COMPUTERS)
ANNUNCIATORPOWER SUPPLY PARTIALLOSS OF CONTROL ROOM ANNUNCIATORS MAYCAUSE LOSS OF ALL CONTROL ROOM ANNUNCIATORSWHEN ALTERNATEUPS ATTEMPTS TO PICK UP ADDITIONALLOADS IF ALLPOWER SUPPLIES ARE FULLYLOADED PARTIALLOSS OF PLANT PAGING SYSTEM PARTIALLOSS OF RADIAK COMMUNICATIONS PARTIALLOSS OF PAGING IN OUTLYING BUILDINGS PARTIALLOSS OF PAGING IN CONTROL BUILDINGEL. 306 INCLUDINGCONTROL ROOM (DUE TO TEMP MOD 90-057)
VPS LOADS PLANTIMPACT 2VBB-UPS1C LOSS OF ESSENTIAL ANDEGRESS LIGHTING LOSS OF COMMUNICATION SYSTEM OPERABILITYOF MAIN STACK RADIATION MONITOR
VPS LOADS PLANTIMPACT 2VBB-UPS1D LOSS OF ESSENTIAL AND EGRESS LIGHTING LOSS OF COMMUNICATION SYSTEM
UPS LOADS PLANTIMPACT 2VBB-UPS1G LOSS OF PMS COMPUTERS (BOP & NSSS)
LOSS OF 3D MONICORE FUNCTIONS LOSS OF DRMS COMPUTER