ML18095A910

From kanterella
Jump to navigation Jump to search
LER 91-017-00:on 910109,sustained Undervoltage Relay Min Drop Out Voltage for All 3 Vital Buses Found Below TS Allowable Value of 91%.Caused by Procedure Inadequacy.New Relay Test Procedures implemented.W/910509 Ltr
ML18095A910
Person / Time
Site: Salem PSEG icon.png
Issue date: 05/09/1991
From: Pollack M, Vondra C
Public Service Enterprise Group
To:
NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-91-017, LER-91-17, NUDOCS 9105150356
Download: ML18095A910 (6)
v • d • e


Text

Public Service Electric.and Gas Company P.O. Box 236 Hancocks Bridge, New Jersey 08038 Salem Generating Station May 9, 1991 U. s. Nuclear Regulatory Commission Document Control Desk Washington, DC 20555

Dear Sir:

SALEM GENERATING STATION LICENSE NO. DPR-70 DOCKET NO. 50-272 UNIT NO. 1 LICENSEE EVENT REPORT 91-017-00 This Licensee Event Report is being submitted pursuant to the requirements of the Code of Federal Regulations 10CFR 50.73(a) (2) (i) (B) . . This ~eport is required to be issued within thirty (30) days o( event discovery.

  • Sincerely yours,
  1. 1£4
J
t/f/~/J~

. A Vondra General Manager -

Salem Operations MJP:pc Distribution

. , ... 9105(!':,-;'

    • I' ' (l~)(l(l(l272 95-2189 (10M) 12-89 r:o1;:

NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION (6-89) APPROVED DMB NO. 3150-0104 EXPIRES: 4/30/92 ESTIMATED BURDEN PER RESPONSE TO COMPLY WTH THIS INFORMATION COLLECTION REQUEST: 50.0 HAS. FORWARD LICENSEE EVENT REPORT (LER) COMMENTS.REGARDING BURDEN ESTIMATE TO THE RECORDS AND REPORTS MANAGEMENT BRANCH (P-530), U.S. NUCLEAR

  • REGULATORY COMMISSION, WASHINGTON, DC 20555, AND TD THE PAPERWORK REDUCTION PROJECT" (3150-0104), OFFICE OF MANAGEMENT AND BUDGET, WASHINGTON, DC 20503.

FACILITY NAME 11) DOCKET NUMBER 12) I PAGE 13]

  • sa1em Generating Station - Unit 1 TITLE 14)

!01s101010121712 1l0Fo1s Tech. Spec. Noncomp1iance; Undervo1taqe Re1ay Setpoints In~orrect1y Set - Procedure Concern EVENT DATE 15) LER l\!UMB~R 16) REPORT DATE 17) OTHER FACILITIES INVOLVED 18)

FACILITY NAMES DOCKET .NUMBERIS)

Sa1em Unit 2 o 15 I o I oI oI3 11 11-THIS REPORT IS SUBMITTED PURSUANT TO THE R~QUIREMENTS OF 10 CFR §: (Check one or more of tho fol/owing/ 111)

OPERATING MODE (9)

I 1 20.402lbl

- 20.40~lcl ,_ 50.73l*ll21(iv)

-- 73.71lb) t-~~~~~~'---+---1 POWER L~fu~L . 11 01 0 -

20.4051*111 Hil 20.4051*111 lllil 20.4051*111 Hilll x 60.38lcll1) 50.3Blcll21 50:131*112Hil 50.73l*ll21M 50.73l*H211viil 60.7311ll2llviiillAI -

73.711c)

OTHER (Specify in Abstr*ct below and in Tt1)(t, NRC Form 366A) 20.405l*H1HM 60.731*112lliil 50.?31*)12llviii)IB)

,___ t--

20.405!*111 IM 50.73(0112) (iii) 50.73l*ll2)i.l LICENSEE CONTACT FOR THIS LER (121 NAME TELEPHONE NUMBER AREA CODE M. J. Po11ack - I.ER Coordinator 6 I 0 I 9 3 13 I 9 I - 12 I 0 12 12

  • COMPLETE ONE LINE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT (13)

CAUSE SYSTEM COMPONENT MANUFAC*

TUR ER R~6o~~:gkE i!*i,!*:.!*!*.*.i':.:!i!:*:!i:::*!*:,i*i.::_:_:i.i*l: CAUSE SYSTEM COMPONENT MANUFAC*

TUR ER I .I I I I I I I I I I I I I I .I I I I I I I I I.I I I I SUPPLEMENTAL REPORT EXPECTED (14) MONTH DAY Y A EXPECTED

~NO SUBMISSION n YES (If ye~, complete EXPECTED SUBMISSION DATE)

  • DATE (151 I I I ABSTRACT '(Limit t~ 1400 spaces, 1:e.. approximately fifreen single*spac~ typewritten linss} (16)

On 4/13/91, the 91.6% sustained undervoltage relay's minimum drop out voltage, for all 3 Vital Busses, were found to be below the Technical Specification minimum allowable value of 91%. This was discovered during Technical Specification Surveillance 4.3.2.1.1 testing which requires monthly testing of undervoltage relay setpoints. New.

procedures (Sl.MD-FT.4KV-0001(Q} (0002 or 0003), "ESFAS Instrumentation Monthly Functional Test-lA (lB or lC) 4KV Vital Bus Under Voltage")

~ere being used (first use) to support the surveillance testing. The surveillance test was last performed on 1/9/91 using procedure M3T,*

"Undervoltage and Underfrequency Trip and Time Response Surveillance Test". It had not been performed since 1/9/91 due to ninth refueling outage activities (operability required only in Modes 1, 2, and 3).

The root cause of this event is attributed procedure inadequacy with contributing factors of test equipment inaccuracies and test methodology. The M3T test procedure, used on 1/9/91, lacked sufficient detail. It addressed performance of all Unit 1 and Unit 2 Vital Bus undervoltage relay and Group Bus undervoltage and underfrequency relay testing. ~s indicated previously, new relay test procedures were used to do the required April surveillance. The new procedures are specific by Unit and by Bus.

NRC Form 366 (6-89)

LICENSEE EVENT REPORT. (LER) TEXT CONTINUATION Salem Generating Station DOCKET NUMBER LER NUMBER PAGE Unit 1 5000272 91-017-00 2 of 5 PLANT AND SYSTEM IDENTIFICATION:

Westinghouse - Pressurized Water Reactor Energy Industry Identification System (EIIS) codes are identified in the text as fxxl.

IDENTIFICATION OF OCCURRENCE:

The Vital Bus 91.6% undervoltage relay setpoints (all three busses).

were found below the mini~um Technical Specification allowable value due to procedure inadequacy.

Event Date: 1/9/91 Discovery Date: 4/13/91 Report Date: 5/09/91 This report was initiated by Incident Report Nos.91-265, 91-266, and 91-267.

CONDITIONS PRIOR TO OCCURRENCE:

Mode 4 (Hot Standby) 9th Refueling/Maintenance Outage - Plant heat up in progress .(outage drawing to a close)

DESCRIPTION OF OCCURRENCE:

On April 13, 1991, at 1430, 1700 and 1950 hours0.0226 days <br />0.542 hours <br />0.00322 weeks <br />7.41975e-4 months <br /> (respectively for each Vital Bus), the 91.6% sustained undervoltage relay's minimum drop out trip setpoint voltage, for all three (3) Vital Busses, was found to be below the Technical Specification minimum allowable value of 91.%. The average trip setpoint was 107.69 VAC (90.3%) and the average reset setpoint was 108.68 VAC (91.4%). This was discovered during monthly Technical Specification Surveillance 4.3.2.1.1 testing of undervoltage relay setpoints. This testing was not performed during the ninth refueling outage due to system constraints (also; mode applicability is modes 1, 2, and 3). New procedures Sl.MD-FT.4KV-000l(Q) (0002 or 0003), "ESFAS Instrumentation Monthly Functional Test-lA (lB or lC) 4KV Vital Bus Under Voltage") were being used (first use} for the testing.

  • The surveillance test was last performed on January 9, 1991, using procedure M3T, "Undervoltage and Underfrequency Trip and Time Response Surveillance Test".

The as-found condition of the Vital Bus relays potentially placed the Unit outside its design basis. To be conservative, the Nuclear Regulatory Commission was notified of this event on April 14, 1991, at 1800 hours0.0208 days <br />0.5 hours <br />0.00298 weeks <br />6.849e-4 months <br /> in accordance with Code of Federal Regulations 10CFR

50. 72 (b) (1) (ii) (B}.

APPARENT CAUSE OF OCCURRENCE:

The root cause of this event is attributed to procedure inadequacy,

LICENSEE EVENT REPORT (LER) TEXT CONTINUATION Salem Generating Station DOCKET NUMBER LER NUMBER PAGE Unit 1 5000272 91-017-00 3 of 5 APPARENT CAUSE OF OCCURRENCE: (cont'd) with contributing factors of test equipment inaccuracies and test methodology. Procedure_M3T did not define the different test equipment setups or specify the test equipment required to support each type of undervoltage or underfrequency relay test. As explained below, personnel error did not contribute to this event as was the case for a similar Unit 2 event (reference LER 311/91-005-00). The Unit 1 calibration (January 9, 1991) had taken place prior to the Unit 2 event. The setpoint deviation was strictly a function of the procedure methodology and normal'relay drift.

When the relay's trip/reset setpoints were checked on January. 9, 1991, the variable power supply's output voltage was varied using thumb-wheel switches. These switches indicate increments, of 0.1 VAC compared to 0.01 VAC for a DVM. The as-found trip/reset setpoints appeared to have been determined by reading the thumb-wheel switch settings.*

When the relay's trip/reset setpoints were checked on April 13, 1991 in accordance with new procedures, the thumb-wheel switches were set

  • to 115 VAC and relay input voltage was adjusted using a variable resistor network. The variable resistor network provided 0.01 VAC increments instead of the previous thumb-wheel method of 0.1 _VAC.

Since the trip/reset setpoints indicated on the DVM were more accurate, this method uncovered the additional v~riable power supply calibration and thumb-wheel switch tolerances.

When the as-found setpoint (on January 9, 1991) was not within M3T's administrative*setpoint span, the relay was recalibrated as follows:

the thumb-wheel switches were set to 108.9 VAC and the relay's "Low Trip" potentiometer was.adjusted until the red LED illuminated. Then the thumb-wheel switches were set to 110.0 VAC and the relay's "Low Trip Deadband" potentiometer*was adjusted until the red LED

  • extinguished. The thumb-wheel switches were changed between the .

required trip and reset voltage to verify proper setpoint actuation.

Since M3T's test methodology added the variable power supply's calibration tolerance to the relay's normal monthly setpoint drift, the relay setpoint was set at a lower voltage than M3T's administrative setpoint spans of 108.75 VAC - 109.05 VAC and 109.85 VAC - 110.15 VAC. Therefore, during the time between the January 9, 1991 test-and the April 13, 1991 test, all nine (9) 91.6% relay trip setpoints drifted below the ~echnical Specification allowable value of 108.2 VAC~

On April 22, 1991, a special test was performed using the January 9, 1991 variable power supply, the other variable power supply used on April 13,* 1991, and a spare 91.6% relay. Test results showed that when the relay trip/reset setpoints were set using the thumb-wheel switches, the as-found setpoints using the DVM and variable resistor*

network were 0.53 VAC and 0.62 VAC lower respectively. When either variable power supply was used to set relay_ setpoints using the new procedure method, the as-found setpoints were within 0.01 VAC and

LICENSEE EVENT REPORT (LER) TEXT CONTINUATION Salem Generating Station DOCKET NUMBER LER NUMBER* PAGE Unit 1 5000272 91-017-00 4 of 5 APPARENT CAUSE OF OCCURRENCE: (cont'd)

O. 02 VAC. Based on the *worst case rela*y drift found during three ( 3) weekly tests per*formed on Unit 2 relays. (0.56 VAC), DVM calibration error* (0.21), and the special test results above (0.53 VAC), the total trip setpoint drift on April 13, 1*991 could have been as much as 1.30 VAC lower compared to the April 13, 1991 average Unit 1 as-found trip setpoint of 1.21 VAC.

ANALYSIS OF OCCURRENCE:

The Vital Bus (lE) 70~ Loss of Voltage, 91.6%.Sustained Degraded

~* Voltage, and 35% Vital Bus Undervoltage Bus Transfer relays monitor the Vital*Bus voltage via 35:1 ratio potential transformers (PTs)~

Each Vital Bus contains one 70% IAV relay three 91.6% Rochester Instrument Systems model PR-2035 Pl-Tl-0 relays, *and one 35% ITE-27H relay. The 70% and 91.6% relays provide input to the Safeguard Equipment Control (SEC) Systems so the SEC can determine Vital Bus emergency loading requirements.

  • On April 13, 1991, all nine (9) 91.6% relays' as-found trip setpoints were less than the minimum Technical Specification allowable value (91%).
  • The relays were then recalibrated to the 91.6% value specified in the applicable Surveillance Test Procedure .

Sl.MD-FT.4KV-0001(Q) (0002 or 0003). Recalibration was completed for each relay of each Vital Bus, at the time the out of specification reading was found. All three (3) Vital Busses relays (total of nine relays) were recalibrated on April 13, 1991~

An engineering analysis (conducted in support of Salem Unit 2 LER 311/91-005-00) previously determined the impact low as-found 91.6%

relay setpoints (90%) would have on Vital Bus motors and loads. For all scenarios, the u~dervoltage relays would ~erform their design function and provide adequate protection to Vital Bus motors and loads. The analysis considered several scenarios *that could result.

in low voltage at the 4KV Vital Busses;. however, those situations were highly improbable during this period since the 500 KV grid voltage* was 108% of 500 KV and all step down transformers equipped with load tap changers

  • Therefore, based on the above analysis, this event did not affect the health or safety of the public. However, since the Technical Specification requirement for the undervoltage relay setpoint was not met, this event is reportable to the commission in accordance with Code of Federal Regulations 10CFR 50.73(a) (2) (i) (B). *
  • CORRECTIVE ACTION:

As indicated previously, the new relay test procedures are unit and bus specific. The new test procedures: 1) include a test equipment connection diagram for each type of relay test; 2) use a variable resistor network to provide 0.01 VAC input voltage increments; 3) increase the minimum administrative trip setpoint from 108.75 VAC to

LICENSEE EVENT REPORT (LER) TEXT CONTINUATION Salem Generating Station DOCKET NUMBER LER NUMBER PAGE Unit 1 5000272 91-017 5 of 5 CORRECTIVE ACTION: (cont'd) 108.90 VAC; and 4) measure relay input voltage at the relay terminals. Additional procedure enhancements will be made to address other human factor and test methodology concerns found during System Engineering's investigation.

General Manager -

Salem Operations MJP:pc SORC Mtg.91-060

Retrieved from "https://kanterella.com/w/index.php?title=ML18095A910&oldid=2409451"