Information Notice 1988-45, Problems in Protective Relay & Circuit Breaker Coordination

Problems in Protective Relay & Circuit Breaker Coordination

ML031150149
Person / Time
Site:	Beaver Valley, Millstone, Hatch, Monticello, Calvert Cliffs, Dresden, Davis Besse, Peach Bottom, Browns Ferry, Salem, Oconee, 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, 05000000, Zimmer, Fort Saint Vrain, Shoreham, Satsop, Trojan, Atlantic Nuclear Power Plant
Issue date:	07/07/1988
From:	Rossi C Office of Nuclear Reactor Regulation
To:
References
IN-88-045, NUDOCS 8806300347
Download: ML031150149 (7)

UNITED STATES

NUCLEAR REGULATORY COMMISSION

OFFICE OF NUCLEAR REACTOR REGULATION

WASHINGTON, D.C. 20555 July 7, 1988 NRC INFORMATION NOTICE NO. 88-45: PROBLEMS IN PROTECTIVE RELAY AND CIRCUIT

BREAKER COORDINATION

Addressees

All holders of operating licenses or construction permits for nuclear power

reactors.

Purpose

This information notice is being provided to alert addressees to a potentially

significant problem concerning the possible lack of protective relay and cir- cuit breaker coordination. 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 do not constitute NRC requirements; therefore, no

specific action or written response is required.

Description of Circumstances

(1) Lack of Circuit Breaker and Protective Relay Coordination at McGuire

Units I and 2 On September 6, 1987, a reactor trip and turbine trip occurred at the

McGuire nuclear station. These trips resulted directly from a lack of

proper circuit breaker coordination on the plant's onsite electrical

distribution system. To facilitate component maintenance, the power

supply to an auxiliary power panel board was shifted to an alternate

source, a 600 V motor control center (MCC). This MCC also provides

power to a compressor in the plant's Instrument air system. A ground

fault developed in the compressor's motor. This fault not only caused

the compressor motor's feeder breaker to open but also caused the feeder

breaker to the 600 V MCC to open. The interruption of power to the MCC

precipitated the loss of the panel board. As a result, the turbine

control system closed the main turbine throttle, governor, and intercept

valves causing the reactor to trip on high pressurizer pressure-,

(2) Lack of Breaker and Protective Relay Coordination at Salem Units 1 & 2 In October 1987, in response to staff questions raised during a fire

protection audit, the licensee of Salem Units 1 and 2 determined that

the lack of circuit breaker coordination in the plant could compromise

8863047Z

I

IN 88-45 July 7, 1988 Page ? of 3 the protection for redundant equipment and/or associated circuits from

common mode failures. As a result, the licensee voluntarily shut down

Unit 2 which was the only unit operating at the time. The resolution

of this issue contributed significantly to the outage that lasted ap- proximately 7 weeks.

(3) Lack of Coordination of Ground Fault Protective Devices at Monticello

In June 1986, the Monticello licensee installed electrical ground fault

detection devices on circuit breakers throughout the onsite electrical

distribution system. The installation of these devices altered the

coordination between circuit breaker, motor control centers, and con- nected loads so that actuation of protective devices in the proper

sequence was no longer assured. In June 1987, at least two operating

events involving the loss of a train of emergency core cooling resulted

from the lack of coordination between protective devices. These problems

were caused by the June 1986 design change which had not adequately con- sidered coordination of the protective devices in conjunction with the

design modification.

Background:

Coordination is the selection and/or setting of protective devices so as to

sequentially isolate only that portion of the system where the abnormality

occurs. To achieve this isolation, it is necessary to set protective devices

so that only the device nearest the fault opens and isolates the faulted circuit

from the system. It is obvious that such selectivity becomes more important

with devices that are closer to the power source, as a greater portion of the

system can be affected.

Backup protective devices are set to operate at some predetermined time interval

after the primary device fails to operate. A backup device is able to withstand

the fault conditions for a longer period than the primary device. If a primary

device fails to clear a fault and the backup device must clear it, then the

design of the protective system becomes suspect.

To optimize the coordination of protective devices, good engineering practice

requires that consideration be given to the following:

(1) available maximum short circuit currents;

(2) time interval between the coordination curves; and

(3) load current.

Discussion:

Other plants may also have problems with relay and breaker coordination. The

staff relies on the exercise of good engineering practice by the designers of

electrical power systems at nuclear power plants to provide for the proper

functioning of protective devices. Breaker coordination is a key fire pro- tection feature if cables for redundant trains pass through a fire area. NRC

IN 88-45 July 7, 1988 Generic Letter (GL) 81-12, "Fire Protection Rule (45 FR 76602, November-19, 1980),"

dated February 20, 1981 required licensees to submit information with regard to

the design description of modifications necessary to meet Section III.G.3 "Fire

Protection of Safe Shutdown Capability," 10 CFR 50, Appendix R, "Fire Protection

Program for Nuclear Power Facilities Operating Prior to January 1, 1979." This

letter set forth general guidelines for protection of safe shutdown capability

from the fire-induced failure of associated circuits. ANSI/IEEE Standard 24?-1986,

"IEEE Recommended Practices for Protection and Coordination of Industrial and

Commercial Power Systems" provides detailed guidance on achieving proper co- ordination.

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 Regional Administrator of the appropriate regional

office.

Charles E. Rossi, Director

Division of Operational Events Assessment

Office of Nuclear Reactor Regulation

Technical Contacts: N. K. Trehan, NRR

(301) 492-0807 E. N. Fields, NRR

(301) 492-1173 Attachment: List of Recently Issued NRC Information Notices

-f

Attachment

IN 88-45 July 7, 1988 LIST OF RECENTLY ISSUED

NRC INFORMATION NOTICES

Information Date of

Notice No. Subject Issuance Tssued to

88-44 Mechanical Binding of 6/24/88 All holders of OLs

Spring Release Device or CPs for nuclear

in Westinghouse Type power reactors.

DS-416 Circuit Breakers

88-43 Solenoid Valve Problems 6/23/88 All holders of OLs

or CPs for nuclear

power reactors.

88-42 Circuit Breaker Failures 6/23/88 All holders of OLs

Due to Loose Charging or CPs for nuclear

Spring Motor Mounting Bolts power reactors.

88-41 Physical Protection 6/22/88 All holders of OLs

Weaknesses Identified or CPs for nuclear

Through Regulatory Ef- power reactors.

fectiveness Reviews (RERs)

88-40 Examiners' Handbook for 6/?2/88 All holders of OLs

Developing Operator or CPs for nuclear

Licensing Examinations power reactors.

88-39 LaSalle Unit 2 Loss of 6/15/88 All holders of OLs

Recirculation Pumps With or CPs for BWRs.

Power Oscillation Event

88-38 Failure of Undervoltage 6/15/88 All holders of OLs

Trip Attachment on General or CPs for nuclear

Electric Circuit Breakers power reactors.

88-37 Flow Blockage of Cooling 6/14/88 All holders of OLs

Water to Safety System or CPs for nuclear

Components power reactors.

88-36 Possible Sudden Loss of RCS 6/8/88 All holders of OLs

Inventory During Low Coolant or CPs for PWRs.

Level Operation

88-35 Inadequate Licensee Performed 6/3/88 All holders of OLs

Vendor Audits or CPs for nuclear

power reactors.

OL = Operating License

CP = Construction Permit

IN 88-45 July 7, 1988 Generic Letter (GL) 81-12, "Fire Protection Rule (45 FR 76602, November 19, 1980),"

dated February 20, 1981 required licensees to submit information with regard to

the design description of modifications necessary to meet Section III.G.3 "Fire

Protection of Safe Shutdown Capability," 10 CFR 50, Appendix R, "Fire Protection

Program for Nuclear Power Facilities Operating Prior to January 1, 1979." This

letter set forth general guidelines for protection of safe shutdown capability

from the fire-induced failure of associated circuits. ANSI/IEEE Standard 242-1986,

"IEEE Recommended Practices for Protection and Coordination of Industrial and

Commercial Power Systems" provides detailed guidance on achieving proper co- ordination.

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 Regional Administrator of the appropriate regional

office.

Charles E. Rossi, Director

Division of Operational Events Assessment

Office of Nuclear Reactor Regulation

Technical Contacts: N. K. Trehan, NRR

(301) 492-0807 E. N. Fields, NRR

(301) 492-1173 Attachment: List of Recently Issued NRC Information Notices

• SEE PREVIOUS PAGE FOR CONCURRENCE

• D:DEST:NRR *C/OGCB: DOEA:NRR

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6/27/88 07// /88 06/23/88

• OGCB:DOEA:NRR *SELB:DEST:NRR *C/SELB:DEST:NRR *SAD/DEST:NRR *RPB:ARM

PKadambi NKTrehan FRosa AThadani TechEd

06/15/88 06/15/88 06/15/88 06/16/88 06/21/88

IN 88-XX

June xx, 1988 No specific action or written response Is required by this information notice.

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

contact listed below or the Regional Administrator of the appropriate regional

office.

Charles E. Rossi, Director

Division of Operational Events Assessment

Office of Nuclear Reactor Regulation

N. K. Trehan, NRR

(301) 492-0807 Attachment: List of Recently Issued NRC Information Notices

D/DOEA:NRR

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C/OGCB:DOEA:NRR

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IN 88-XX

June xx, 1988 No specific action or written response is required by this information notice.

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

contact listed below or the pOegional i'dministrator of the appropriate regional

office.

Charles E. Rossi, Director

Division of Operational Events Assessment

Office of Nuclear Reactor Regulation

N. K. Trehan, NRR

(301) 492-0807 Attachment: List of Recently Issued NRC Information Notices

D/DOEA:NRR C/OGCB:DOEA:NRR

CERossi CHBerlinger

06/ /88 06/ /88 OGCBDOEA:NRR SELB:DEST:NRR C/SELB:DE T:NRR SAD/DEST: ~f RPB:ARM

PKada bi NKTrehan FRosa ATh dani TechEd - 6 4:? t#

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