Information Notice 1991-81, Switchyard Problems That Contribute to Loss of Offsite Power

Switchyard Problems That Contribute to Loss of Offsite Power

ML031190398
Person / Time
Site:	Beaver Valley, Millstone, Hatch, Monticello, Calvert Cliffs, Dresden, Davis Besse, Peach Bottom, Browns Ferry, Salem, Oconee, Mcguire, Nine Mile Point, Palisades, Palo Verde, Perry, Indian Point, Fermi, Kewaunee, Catawba, Harris, Wolf Creek, Saint Lucie, Point Beach, Oyster Creek, Watts Bar, Hope Creek, Grand Gulf, Cooper, Sequoyah, Byron, Pilgrim, Arkansas Nuclear, Three Mile Island, Braidwood, Susquehanna, Summer, Prairie Island, Columbia, Seabrook, Brunswick, Surry, Limerick, North Anna, Turkey Point, River Bend, Vermont Yankee, Crystal River, Haddam Neck, Ginna, Diablo Canyon, Callaway, Vogtle, Waterford, Duane Arnold, Farley, Robinson, Clinton, South Texas, San Onofre, Cook, Comanche Peak, Yankee Rowe, Maine Yankee, Quad Cities, Humboldt Bay, La Crosse, Big Rock Point, Rancho Seco, Zion, Midland, Bellefonte, Fort Calhoun, FitzPatrick, McGuire, LaSalle, Fort Saint Vrain, Shoreham, Satsop, Trojan, Atlantic Nuclear Power Plant
Issue date:	12/16/1991
From:	Rossi C Office of Nuclear Reactor Regulation
To:
References
IN-91-081, NUDOCS 9112110011
Download: ML031190398 (9)

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UNITED STATES

NUCLEAR REGULATORY COMMISSION

OFFICE OF NUCLEAR REACTOR REGULATION

WASHINGTON, D.C. 20555 December 16, 1991 NRC INFORMATION NOTICE 91-81: SWITCHYARD PROBLEMS THAT CONTRIBUTE TO

LOSS OF OFFSITE POWER

Addressees

All holders of operating licenses or construction permits for nuclear power

reactors.

Purpose

The U.S. Nuclear Regulatory Commission (NRC) is issuing this information notice

to alert addressees to several problems associated with plant switchyards. It

is expected that recipients will review the information for applicability to

their facilities and consider actions, as appropriate, to avoid similar problems.

However, suggestions contained in this information notice are not NRC require- ments; therefore, no specific action or written response is required.

Description of Circumstances

On April 23, 1991, a complete loss of offsite power occurred at the Vermont

Yankee Nuclear Power Station as a result of maintenance activities in the

switchyard. Maintenance workers were installing a new battery for one of the

two non-lE 125 VDC buses. The two normally independent buses were cross tied

through the swing battery charger 4A-5A after defeating a mechanical interlock

(Figure 1). Furthermore, the licensee was paralleling the battery chargers

on bus DC-4A without a battery on this bus. When the 4A-5A battery charger

output breaker feeding bus DC-5A was opened prior to connection of the new

battery 4A to bus DC-4A, a voltage transient propagated through the switchyard

DC control system that caused all but one of the 345kV and 115kV circuit

breakers to trip and lock open. The loss of offsite power which occurred

caused a main turbine and automatic reactor trip. Restoration of full offsite

power took thirteen hours.

The NRC dispatched an augmented inspection team (AIT) to investigate this

event, and the following generic concerns were identified by the team in its

report (50-217/91-13): (1) a lack of preventive maintenance on battery

chargers, (2) presence of sensitive components in logic cards making them

susceptible to failure, (3) switchyard protective relays that were susceptible

to a single failure, and (4) a lack of clear authority over the switchyard

during emergency conditions.

9112110011 /

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page 2 of 3

- - .... , Anntpriance char

Lack of Preventive ,-- - switchyard

chargers (4A, B, and 4A-5A) in the fn

Three of the four

non-lE battery

condition at the time of the event. filter

in a degraded the output

DC control system werebattery chargers, manufactured by Exidf, fuses in one iiter

each of the degraded The problems included blown capacitor *inthe

was not functional. another, and a failed

circuit

blown and wrong-sized fuses

in

charger output filter circuit r.ad

circuit, If the 4A-5A battery have been m(itigate

third filter circuit. effect of the voltage transient may problems resultCC

The

been functional, the power might have been prevented. battery chargers.

IlTe

and loss of offsite maintenance on the

preventive and it appeared

directly from infrequent maintenance program for the chargers battery chargers aigre

licensee had no regular in 1985. These is

was performed

that the last maintenance testing or preventive maintenance includit.u

and no surveillance system, not safety related at this facility, the switchyard battery associated distribu- and

required. However, their associated chargers, thequitchyard batteries, auxiliary electrical power system

and is required

is part of the

tion panels, plant's Technical Specifications.

to be operable by the

in Logic Cards

Sensitive Components

switchyard DC control 'y"u,, .baI_ . v circuit breakers

The voltage spike in the of two switchyard ard

failure units (SBFUS) breakers in the by AREA

-4zks

in the stuck breaker reaction that caused most of the are manufactured

which led to a chain to trip and lock open. These

SBFUs

Electric

115kV switchyard previous models were made by the Westinghouse

and units that are not as suscep- Brown Boveri, has developed new

zener diodes.

Corporation. The manufacturer because the new units do not contain

tible to voltage spikes

Failure

Relays Subject to a Single t%.,

Protective

from a single bus (DC-4A) even though a

are powered This desig.

All of the SBFU relays in the switchyard DC control system. similar proteccti;-

DC buses are available failure. Other facilities may havecause failure.

subject to a single could be vulnerable

to a common

relaying designs that

Coditions

c-..4+,4iiizrnrd Under Emergenc

a lack of coIrmunications

power was delayed because of (T&D) personnel.

offsite

The restoration of and the transmission and distribution the switchyard. The

between plant staff T&D is responsible

for operating

conditions, the responsi- Under normal that, under emergency conditions, does not

specifies the procedure

licensee's procedure to the plant staff. However, suggest the need to clarify

bility is transferred problems

These operational other emergency condi- define "emergency." during a loss of offsite power or

switchyard authority switchyard activities

are important.

tions when timely

Problems

Example of Switchyard Communication

Additional can be seen in Ar

problems in the switchyard Unit i, on

Another example of

communication Nuclear Generating Station, at the McGuire T&D personnel caused

event that took placeThe unit tripped from 100% power when

February 11, 1991.

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IN 91-81 December 16, 1991 a loss of all offsite power while testing a modification to the protective

relay circuitry in the 230 kV switchyard. Since the majority of the switchyard

is outside of the plant equipment boundary, the T&D personnel did not notify

the station operations personnel that work was in progress even though switch- yard activities can impact the station. Prior to this event there was no

agreement between station operations and T&D personnel on how to handle switch- yard activities outside the plant equipment boundary. Subsequent to this

event, a work control policy was established to provide improved communication

between the station operations personnel and T&D personnel.

No specific action or written response is required by this information notice.

If you have any questions about this matter, please contact one of the technical

contacts listed below or the appropriate Office of Nuclear Reactor Regulation

(NRR) project manager.

arles E. Rossi Director

Division of Operational Events Assessment

Office of Nuclear Reactor Regulation

Technical contacts: Cliff Anderson, Region I

(215) 337-5376 Peter Kang, NRR

(301) 504-0779 David Skeen, NRR

(301) 504-1174 Attachments:

1. Figure 1: Switchyard House DC Distribution

One Line Diagram

2. List of Recently Issued NRC Information Notices

BUS 8 BUS 11 I - -1 - - - - - - --- I

I )-ldTL .) I

I I I

I %I a1 Io I. ,n 1 LMECHAN ICAL

- - --- , INTERLOCK-

)16 )3 )I8 I I )30 32

1)SI

DC DISTRIBUTIOw PANEL OC-SA - OISTRf8UT ION PANEL DC-4A

SIYD BATT SWYDBATT

SA 4A (

0D

M f0Co

Figure 1 Switchyard House DC Distribution One Line Diagram (D CIO

'0 D

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Attachment 2 IN 91-81 December 16, 1991 LIST OF RECENTLY ISSUED

NRC INFORMATION NOTICES

I tformation Date of

Notice to. Subject Issuance Issued to

91-80 Failure of Anchor 12/11/91 All holders of OLs or CPs

Head Threads on Post- for nuclear power reactors.

Tensioning System During

Surveillance Inspection

9I-79 Deficiencies in the 12/06/91 All holders of OLs or CPs

Procedures for Instal- for nuclear power reactors.

ling Thermo-Lag Fire

Barrier Materials

88-92, Potential for Spent 11/29/91 All holders of OLs or CPs

Supp. 1 Fuel Pool Draindown for nuclear power reactors.

Status Indication of 11/28/91 All holders of OLs or CPs

Control Power for for nuclear power reactors.

Circuit Breakers Used

in Safety-Related Appli- cations

9j-57, Substandard, Refur- 11/27/91 All holders of OLs or CPs

S..pp. 1 bished Potter & Brum- for nuclear power reactors.

field Relays Repre- sented as New

01 -77 Shift Staffing at 11/26/91 All holders of OLs or CPs

Nuclear Power Plants for nuclear power reactors.

91-76 10 CFR Parts 21 and 11/26/91 All holders of OLs or CPs

50.55(e) Final Rules and vendors for nuclear

power reactors.

91-75 Static Head Corrections 11/25/91 All holders of OLs or CPs

Mistakenly not Included for nuclear power reactors.

in Pressure Transmitter

Calibration Procedures

91-74 Changes in Pressurizer 11/25/91 All holders of OLs or CPs

Safety Valve Setpoints for nuclear power reactors.

Before Installation

OL = Operating License

CP = Construction Permit

IN 91-81 December 16, 1991 a loss of all offsite power while testing a modification to the protective

relay circuitry in the 230 kV switchyard. Since the majority of the switchyard

is outside of the plant equipment boundary, the T&D personnel did not notify

the station operations personnel that work was in progress even though switch- yard activities can impact the station. Prior to this event there was no

agreement between station operations and T&D personnel on how to handle switch- yard activities outside the plant equipment boundary. Subsequent to this

event, a work control policy was established to provide improved communication

between the station operations personnel and T&D personnel.

No specific action or written response is required by this information notice.

If you have any questions about this matter, please contact one of the technical

contacts listed below or the appropriate Office of Nuclear Reactor Regulation

(NRR) project manager. Orgnal Signid by

Charles E. Rossi, Director Charles E.Rossi

Division of Operational Events Assessment

Office of Nuclear Reactor Regulation

Technical contacts: Cliff Anderson, Region I

(215) 337-5376 Peter Kang, NRR

(301) 504-0779 David Skeen, NRR

(301) 504-1174 Attachments:

1. Figure 1: Switchyard House DC Distribution

One Line Diagram

2. List of Recently Issued NRC Information Notices

• See previous concurrence

OFC  :*OEAB:NRR  : *RI  :*SC:OEAB:NRR:*ADM:RPB  :*C:SELB:NRR :*C:OEAB:NRR

_____ _____ __ _ _ ____________ ____ - ------

NAME :DSkeen  : CAnderson :RDennig :JMain :FRosa :AChaffee

____________ ------------ ______ __ __ ____________ - ------

_____

DATE :10/01/91  : 10/01/91 :11/05/91 :10/01/91 :11/05/91 :11/14/91 OFC  :*C:OGCB:NRR :D:DOEA  :

___----- -------  :-- -- ?- ----------  :------------:------------ ------------ -------

NAME :CBerlinger  :  :

DATE :11/25/91 :12////91 OFFICIAL RECORD COPY

Document Name: IN 91-81

IN 91-XX

November xx, 1991 there was no agreement between station operations and T&D personnel on how to

handle switchyard activities outside the plant owned equipment boundaries.

Subsequent to this event, a work control policy was established to provide

improved communication between the station operations personnel and T&D

personnel.

The staff is providing this information as an early notification of a matter

that could become significant and that the NRC staff is continuing to consider.

Upon completing its evaluation, the staff may require licensees to take

specific actions. No specific action or written reponse is required by this

information notice. If you have any questions about this matter, please contact

the technical contacts below or the appropriate Office of Nuclear Reactor

Regulation (NRR) project manager.

Charles E. Rossi, Director

Division of Operational Events Assessment

Office of Nuclear Reactor Regulation

Technical contacts: Cliff Anderson, Region I

(215) 337-5376 Peter Kang, NRR

(301) 492-0779 David Skeen, NRR

(301) 492-1174 Attachment:

1. Figure 1: Switchyard House DC Distribution

One Line Diagram

2. List of Recently Issued NRC Information Notices

• See previous concurrence

OFC  :*OEAB:NRR  : *RI  :*SC:OEAB:NRR:*ADM:RPB  :*C:SELB:NRR :*C:OEAB:NRR

_____ ____________ - ----------- ____________ ____________ ____________ - ------

NAME :DSkeen  : CAnderson :RDennig :JMain :FRosa :AChaffee  :

DATE :10/01/91  : 10/01/91 :11/05/91 :10/01/91 :11/05/91 :11/14/91

• 11 9)

OFC :C: UP, Y :D:DOEA

NAME :CBerlinger :CRossi I::

DATE : 1;/I91  : / /91 OFFICIAL RECORD COPY

Document Name: IN/SWITCHYARD/SKEEN

IN 91-XX

October xx, 1991 The staff is providing this information as an early notification of a matter

that could become significant and that the NRC staff is continuing to consider.

Upon completing its evaluation, the staff may require licensees to take

specific actions. No specific action or written reponse is required by this

information notice. If you have any questions about this matter, please contact

the technical contacts below or the appropriate Office of Nuclear Reactor

Regulation (NRR) project manager.

Charles E. Rossi, Director

Division of Operational Events Assessment

Office of Nuclear Reactor Regulation

Technical contacts: Cliff Anderson, Region I

(215) 337-5376 Peter Kang, NRR

(301) 492-0779 David Skeen, NRR

(301) 492-1174 Attachment: List of Recently Issued NRC Information Notices

• See previous concurrence

OFC  :*OEAB:NRR  : *RI :S :NRR :*ADM:RPB :C:SELB.4NRR :C:OpAB:NRR  :

Rb g  :------------n:F---o  : f_-------- ------

NAME :DSkeen  : CAnderson :Re~ig rJai c~oa :AChaffee  :

,-- -- -  : -- - ------- :- - -

__ -:--- ---_-_ _-__ - - - __-___

- _

DATE :10/01/91  : 10/01/91  :// / As /91 :10/01/91  : 1 /$/91  : [(//K/91 OFC :C:OGCB:NRR :D:DOEA  :

NAME :CBerlinger :CRossi  :

DATE : / /91  : / /91  :

OFFICIAL RECORD COPY

Document Name: IN/SWITCHYARD/SKEEN

No specific action or written reponse is required by this information notice.

If you have any questions about this matter, please contact the technical

contacts below or the appropriate Office of Nuclear Reactor Regulation project

manager.

Charles E. Rossi, Director

Division of Operational Events Assessment

Office of Nuclear Reactor Regulation

Technical contacts: Cliff Anderson, Region I

(215) 337-5376 Peter Kang, NRR

(301) 492-0779 David Skeen, NRR

(301) 492-1174 Attachment: List of Recently Issued NRC Information Notices

pfr TGLECoA

OFC :OEAB:NRR  : RI :SC:OEAB:NRR :ADM:RPB :C:SELB:NRR :C:OEAB:NRR

____---- ------ --- " - tF------------ :------------ :------------ :------------:---

NAME :DSkeen j  : CAnderson :RDennig :JMain - 9 :FRosa :AChaffee

DATE :/O/ 1/91  : 0/ //91  : / /91 :10/1 /91  : / /91  : / /91 OFC :C:OGCB:NRR :D:DOEA  :

NAME :CBerlinger :CRossi  :  :  :

DATE: / /91  : / /91  :  :

OFFICIAL RECORD COPY

Document Name: IN/SWITCHYARD/SKEEN