Information Notice 1993-75, Spurious Tripping of Low-Voltage Power Circuit Breakers with GE RMS-9 Digital Trip Units

Spurious Tripping of Low-Voltage Power Circuit Breakers with GE RMS-9 Digital Trip Units

ML031070324
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:	09/17/1993
From:	Grimes B Office of Nuclear Reactor Regulation
To:
References
IN-93-075, NUDOCS 9309140046
Download: ML031070324 (13)

UNITED STATES

NUCLEAR REGULATORY COMMISSION

OFFICE OF NUCLEAR REACTOR REGULATION

WASHINGTON, D.C. 20555 September 17, 1993 NRC INFORMATION NOTICE 93-75: SPURIOUS TRIPPING OF LOW-VOLTAGE POWER CIRCUIT

BREAKERS WITH GE RMS-9 DIGITAL TRIP UNITS

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 the potential for loss of safety-related buses

or individual loads because of spurious tripping of low-voltage circuit

breakers fitted with General Electric (GE) RMS-9 digital trip units. 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 requirements; therefore, no specific action or written response is

required.

Description of Circumstances

In October 1992, the Tennessee Valley Authority (TVA) reported to the NRC

pursuant to Part 21 of Title 10 of the Code of Federal Regulations (10 CFR

Part 21) that the ungrounded, delta-connected, 480-volt distribution system at

its Browns Ferry Nuclear Plant (BFN) had experienced short-duration, high- amplitude current transients (possibly high-frequency electrical noise spikes)

that caused unwanted tripping of some GE AK-type circuit breakers fitted with

GE RMS-9 solid-state digital trip units. These units have a low-pass filter

(described by some as a "holdoff circuit") that is supposed to exclude most

transients of this sort. However, TVA reported that testing of the trip units

revealed that the instantaneous trip function of the trip unit would respond

to current transients as short as 100 microseconds and trip the breaker when

the peak amplitude of the current pulse or spike was sufficiently above the

instantaneous trip setpoint of the RMS-9 unit.

On August 4, 1993, the NRC was informed that the Maine Yankee Nuclear Power

Plant had a similar situation that the licensee described as sympathetic

tripping of two safety-related, RMS-9-equipped breakers, one of which was a

load breaker (with longtime and instantaneous trip functions) and the other a

motor control center (MCC) feeder breaker (with longtime-shorttime trips).

Both of the affected breakers were fed from the plant's delta-connected,

480-volt, engineered safeguards buses which are of an ungrounded design like

9309140046 PoD . o

v-I

IN 93-75 September 17, 1993 those at Browns Ferry. The trips may have been initiated by current spikes

caused by an intermittent ground fault on the boric acid makeup tank startup

heaters, a nonsafety-related load on that bus; although their breaker did not

trip. Also, the trips occurred during the process of ground isolation which

may have created or contributed to transients on the busses. However, the

transients were not sufficient to trip other RMS-9-equipped breakers, some of

which, acting as Class IE isolation devices, are meant to protect the safety- related busses from faults and overloads on nonsafety-related circuits, which

are also not environmentally qualified.

Discussion

In both these cases, the digital RMS-9 units were installed in GE AK-type low- voltage power circuit breakers as conversion kits to replace either earlier

versions of solid state units or the electromechanical EC-type series overload

trip units previously used. According to the manufacturer, GE Electrical

Distribution and Control (ED&C) in Plainville, Connecticut, the RMS-9 digital

electronic units were first available in October 1986 and the last of the

previous models, the analog electronic "MicroVersatrip" MVT-9 units, were

supplied in about January 1987.

GE Nuclear Energy (GE NE) in San Jose, California, has informed the NRC that

it is developing a modification specifically for the affected RMS-9 units at

Browns Ferry ta-makeathem-less-susceptible to unwanted tripping due to these

transients. In addition, ED&C is undertaking a systems study in cooperation

with GE NE and Maine Yankee to determine the conditions conducive to these

transients and to develop long-term or permanent solutions. These may be

software and/or hardware modifications to the trip units and/or recommended

modifications to the plant systems to prevent the unwanted tripping. Once

fully developed and tested, any trip unit updates would be included in new

RMS-9 units and GE switchgear service shops would install them in existing

units. Trip units could then be interchanged in breakers in the field or

purchased with new or replacement breakers.

Neither GE NE nor GE ED&C has issued any Service Information Letters (SILs) or

Service Advice Letters (SALs), respectively, on this subject as yet. However, GE product literature indicates that the units can be set up with their

instantaneous trip functions disabled. This may be more appropriate for

certain applications (typically, feeder breakers) which, for purposes of

breaker coordination, would rely on a short time trip function for fault

protection, keeping the instantaneous trip functions only on load breakers.

The NRC is attempting to obtain sufficient information to better define the

range of applications of these units, envelop the conditions likely to make

the equipment susceptible to the problem, and identify any common-mode

initiators that may exist. GE has confirmed that its evidence suggests that

ungrounded systems (particularly if delta-connected) are apparently the most

susceptible to the kind of transients to which the RMS-9s can respond. RMS-9 units, used only on low-voltage switchgear, are used in certain models of GE

-J

IN 93-75 September 17, 1993 molded-case circuit breakers, and "Power Break" circuit breakers in addition

to the metalclad breakers. Although, none except those on metalclad air

circuit breakers have reportedly experienced this problem, other RMS-9s may

not have been exposed to the transients of concern. Meanwhile, GE NE and the

GE Switchgear Apparatus Service Shop in Atlanta, Georgia, are currently

assisting Maine Yankee in exchanging (at least temporarily) several critical

RMS-9-equipped breakers for ones fitted with EC-type series trip units.

In terms of safety significance, these incidents of spurious tripping, although somewhat isolated, raise the concern that a common-mode initiator of

intermittent ground faults on nonsafety-related and unqualified circuits, such

as a loss-of-coolant accident or high-energy line break, could conceivably

cause propagation of current spikes to multiple portions of an electrical

distribution system. They may not trip Class IE isolation breakers not fitted

with RMS-9s, and may not trip some with RMS-9s, but could result in unwanted

tripping of other RMS-9-equipped breakers and the attendant loss of vital

loads, possibly in more than one train.

This information notice requires no specific action or written response. If

you have any questions about the information in this notice, please contact

one of the technical contacts listed below or the appropriate Office of

Nuclear Reactor Regulation (NRR) project manager.

Brian K. Grimes, Director

Divis4on of Operating Reactor Support

Office of Nuclear Reactor Regulation

Technical contacts: Stephen D. Alexander, NRR

(301) 504-2995 Kamalakar R. Naidu, NRR

(301) 504-2981 Attachment:

List of Recently Issued NRC Information Notices

a

Attachment

In 93-75 September 17 1993 Page I of I

49) 0,

IB 3 U faf

4C f*

LIST OF RECENTLY ISSUED

NRCINFORNATION NOTICES

Informatlon Date Ot

Notice No. Subject Issuance Issued to

2

93-74 High Temperatures Reduce 09/16/93 All holbers of OLs or CPs

Limitorque AC Motor for nuclear power reactors.

Operator Torque

93-73 Criminal Prosecution of 09/15/93 All KRClicensees.

Nuclear Suppliers for

Wrongdoing

93-72 Observations from Recent 09/14/93 All holders of OLs or CPs

Shutdown Risk and Outage for nuclear power reactors.

Nanagement Pilot Team otu

Inspections

93-71 Fire at Chernobyl Unit 2 09/13/93 All holders of OLs or CPs

for nuclear power reactors.;

to a cco

93-70 Degradation of Boraflex 09/10/93 All holders of OLs or CPs

Neutron Absorber Coupons for nuclear power reactors.

93-69 Radiography Events at 09/02/93 All holders of OLs or CPs

Operating Power Reactors for nuclear power reactors

and all radiography

licensees.

93-68 Failure of Pump Shaft 09/01/93 All holders of OLs or CPs

Coupling Caused by for nuclear power reactors.

Temper Embrittlement

during Nanufacture

) 92-16, Supp. 2 Loss of Flow from the

Residual Heat Removal

Pump during Refueling

08/23/93 All holders of OLs or CPs

for nuclear power reactors.

Cavity Draindown

93-67 Bursting of High 08/16/93 All holders of OLs or CPs i"

Pressure Coolant for nuclear power reactors. 2o

Injection Steam Line 0z V

Rupture Discs Injures

Plant Personnel f 0

Q

C*

OL - Operating License 41 h-J

°e

CP

• Construction Permit

0.

z

IN 93-75 September 17, 1993 molded-case circuit breakers, and "Power Break" circuit breakers in addition

to the metalclad breakers. Although, none except those on metalclad air

circuit breakers have reportedly experienced this problem, other RMS-9s may

not have been exposed to the transients of concern. Meanwhile, GE NE and the

GE Switchgear Apparatus Service Shop in Atlanta, Georgia, are currently

assisting Maine Yankee in exchanging (at least temporarily) several critical

RMS-9-equipped breakers for ones fitted with EC-type series trip units.

In terms of safety significance, these incidents of spurious tripping, although somewhat isolated, raise the concern that a common-mode initiator of

intermittent ground faults on nonsafety-related and unqualified circuits, such

as a loss-of-coolant accident or high-energy line break, could conceivably

cause propagation of current spikes to multiple portions of an electrical

distribution system. They may not trip Class 1E isolation breakers not fitted

with RMS-9s, and may not trip some with RMS-9s, but could result in unwanted

tripping of other RMS-9-equipped breakers and the attendant loss of vital

loads, possibly in more than one train.

This information notice requires no specific action or written response. If

you have any questions about the information in this notice, please contact

one of the technical contacts listed below or the appropriate Office of

Nuclear Reactor Regulation (NRR) project manager.

orig /s/'d by AEChaffee/for

Brian K. Grimes, Director

Division of Operating Reactor Support

Office of Nuclear Reactor Regulation

Technical contacts: Stephen D. Alexander, NRR

(301) 504-2995 Kamalakar R. Naidu, NRR

(301) 504-2981 Attachment: List of Recently Issued NRC Information Notices

• See previous concurrence l

OFFICE VIB/DRIL VIB/DRIL SC/VIB/DRIL BC/VIB/DRIL TECHED

NAME SALEXANDER* KNAIDU* GCWALINA* LNORRHOLM* DGABLE*

DATE 8/05/93 8/05/93 8/11/93 8/11/93 8/06/93 YES YES YES YES NO

COPY

OFFICE D/DRIL/NRR BC/SELB/DEST BC/OGCB/DORS D DORS

NAME CEROSSI* CBERLINGER* GMARCUS* BK~k

DATE 8/13/93 8/13/93 8/23/93 9/1 //93 YES YES NO YES NO YES NO

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\~d IN 93-75 September 17, 1993 molded-case circuit breakers, and "Power Break" circuit breakers in addition

to the metalclad breakers. Although, none except those on metalclad air

circuit breakers have reportedly experienced this problem, other RMS-9s may

not have been exposed to the transients of concern. Meanwhile, GE NE and the

GE Switchgear Apparatus Service Shop in Atlanta, Georgia, are currently

assisting Maine Yankee in exchanging (at least temporarily) several critical

RMS-9-equipped breakers for ones fitted with EC-type series trip units.

In terms of safety significance, these incidents of spurious tripping, although somewhat isolated, raise the concern that a common-mode initiator of

ground faults on nonsafety-related and unqualified circuits, such as a loss- of-coolant accident or high-energy line break, could conceivably cause

propagation of current spikes to multiple portions of an electrical

distribution system. They may not trip Class lE isolation breakers not fitted

with RMS-9s, but could result in unwanted tripping of RMS-9-equipped breakers

and the attendant loss of vital loads, possibly in more than one train.

This information notice requires no specific action or written response. If

you have any questions about the information in this notice, please contact

one of the technical contacts listed below or the appropriate Office of

Nuclear Reactor Regulation (NRR) project manager.

Brian K. Grimes, Director

Division of Operating Reactor Support

Office of Nuclear Reactor Regulation

Technical contacts: Stephen D. Alexander, NRR

(301) 504-2995 Kamalakar R. Naidu, NRR

(301) 504-2981 Attachment: List of Recently Issued NRC Information Notices

• See Drevious concurrence

OFFICE VIB/DRIL VIB/DRIL SC/VIB/DRIL BC/VIB/DRIL TECHED

NAME SALEXANDER* KNAIDU* GCWALINA* LNORRHOLM* DGABLE*

DATE 8/05/93 8/05/93 8/11/93 8/11/93 8/06/93 COPY YES YES YES YES NO

OFFICE D/DRIL/NRR BC/SELB/DEST BC/OGCB/DORS _DO_ _ _

NAME CEROSSI* CBERLINGER* GMARCUS* BKGK S /93ES

DATE 8/13/93 8/13/93 8/23/93 9 93 / /93 COPY YES YES YES NO YES NO YES NO

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IN 93-XX

September XX, 1993 are currently

GE Switchgear Apparatus Service Shop in Atlanta, Georgia, several critical

assisting Maine Yankee in exchanging (at least temporarily)

fitted with EC-type series trip units.

RMS-9-equipped breakers for ones

tripping, In terms of safety significance, these incidents of spurious initiator of

although somewhat isolated, raise the concern that a common-mode

such as a loss- ground faults on nonsafety-related and unqualified circuits, cause

of-coolant accident or high-energy line break, could conceivably

propagation of current spikes to multiple portions of an electrical breakers not fitted

distribution system. They may not trip Class IE isolation breakers

with RMS-9s, but could result in unwanted tripping of RMS-9-equipped than one train.

and the attendant loss of vital loads, possibly in more

response. If

This information notice requires no specific action or writtenplease contact

you have any questions about the information in this notice, Office of

one of the technical contacts listed below or the appropriate

Nuclear Reactor Regulation (NRR) project manager.

Brian K. Grimes, Director

Division of Operating Reactor Support

Office of Nuclear Reactor Regulation

Technical contacts: Stephen D. Alexander, NRR

(301) 504-2995 Kamalakar R. Naidu, NRR

(301) 504-2981 Attachment: List of Recently Issued NRC Information Notices

• See previous concurrence

VIB/DRIL VIB/DRIL SC/VIB/DRIL BC/VIB/DRIL TECHED

OFFICE

SALEXANDER* KNAIDU* GCWALINA* LNORRHOLM* DGABLE*

NAME

8/05/93 8/05/93 8/11/93 8/11/93 8/06/93 DATE

YES YES YES NO

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OFFICE D/DRIL/NRR BC/SELB/DEST BC/OGCB/DORS D/DORS____l

NAME CEROSSI* CBERLINGER* GMARCUS9 BKGRIMES

8/13/93 8/13/93 /93 9/ /93 / /93 DATE

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IN 93-XX

August XX, 1993 In terms of saf significance, these incidents of spurious tripping, although somewhat olated, raise the concern that a common-mode initiator of

ground faults on non fety-related and unqualified circuits, such as a loss- of-coolant accident or igh-energy line break, could conceivably cause

propagation of current stkes to multiple portions of an electrical

distribution system. They ay not trip Class 1E isolation breakers not fitted

with RMS-9s, but could resul in unwanted tripping of RMS-9-equipped breakers

and the attendant loss of vita loads, possibly in more than one train.

This information notice requires X specific action or written response. If

you have any questions about the inf mation in this notice, please contact

one of the technical contacts listed b ow or the appropriate Office of

Nuclear Reactor Regulation (NRR) project anager.

\1/

Brian K. imes, Director

Division o perating Reactor Support

Office of Nuc ear Reactor Regulation

Technical contacts: Stephen D. Alexander, NRR

(301) 504-2995 Kamalakar R. Naidu, NRR

(301) 504-2981 Attachment: List of Recently Issued NRC Information Notices

• Cne n-^%Aiorl ennenollrranr

OFFICE VIB/DRIL VIB/DRIL SC/VIB/DRIL BC/VIB/DRIL TECHED

NAME SALEXANDER* KNAIDU* GCWALINA* LNORRHOLM* DGABLE*

DATE 8/05/93 8/05/93 8/11/93 8/11/93 8/06/93 COPY YES YES YES YES NO

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IN 93-XX

August XX, 199:.3 In terms of safety sig *ficance, these incidents of spurious tripping, although somewhat isolate, raise the concern that a common-mode initiator of

ground faults, such as a 1 s-of-coolant accident or high-energy line break, could conceivably cause prop ation of current spikes to multiple portions of

an electrical distribution sys em, which could result in spurious tripping of

RMS-9-equipped breakers and the ttendant loss of vital loads, possibly in

more than one train.

This information notice requires no ecific action or written response. If

you have any questions about the infor tion in this notice, please contact

one of the technical contacts listed be w or the appropriate Office of

Nuclear Reactor Regulation (NRR) project nager.

\l/

Brian K. mies, Director

Division o Operating Reactor Support

Office of Nu lear Reactor Regulation

Technical contacts: Stephen D. Alexander, NRR

(301) 504-2995 Kamalakar R. Naidu, NRR

(301) 504-2981 Attachment: List of Recently Issued NRC Information Notices

• See previous concurrence

OFFICE VIB/DRIL VIB/DRIL SC/VIB/DRIL BC/VIB/DRIL TECHED

NAME SALEXANDER* KNAIDU* GCWALINA* LNORRHOLM* DGABLE*

DATE 8/05/93 8/05/93 8/11/93 /11/93 8/06/93 COPY YES YES YES YES NO

OFFICE D/DRIL/NRR BC/SELB/DEST 4,BC/OGCB/DORS XD/DORS

NAME CEROSSI* CBERLINGER* of2"MARCUS / BKGRIMES

DATE 8/13/93 8/13/93 e_ 8/ /93 _8_ /_/93

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IN 93-XX

August XX, 1993 This information notice quires no specific action or written response. If

you have any questions abot the information in this notice, please contact

one of the technical contact listed below or the appropriate Office of

Nuclear Reactor Regulation (NR project manager.

B an K. Grimes, Director

Div ion of Operating Reactor Support

Offic of Nuclear Reactor Regulation

Technical contacts: Stephen D. Alexander,

(301) 504-2995 Kamalakar R. Naidu, NRR

(301) 504-2981 Attachment: List of Recently Issued NRC Information Not

• See previous concurrence

OFFICE VIB/DRIL VIB/DRIL SCAV~RIL BCB/DRIL TECHED

SALEXANDER* KNAIDU* G L OAOLM _ DGABLE*

NAME

8/05/93 8/05/93 8/1 /93 8/l/93 8/06/93 DATE

COPY YES YES YES YES NO NO

OFFICE D/DRUIER,. BC/SELB/D0 BC/OGCB/DORS D/DORSl

NAME C ACBERLINGEV GMARCUS BKGRIMES

DATE 8/1,393 8/L5/93 8/ /93 ll

YES NO YES NO YES NO YES NO YES NO

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OFFICIAL RECORD COPY UUuVrLcr1 I 11PULc.

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IN 93-XX

August XX, 1993 addition, the NRC has ned that certain early versions of the RMS-9 units

had instantaneous trip fu tions that could not be bypassed or the time delay

adjusted, indicating a poss e misapplication problem.

The NRC is attempting to btain sufficient information to better define

the range of applications of the units, envelope the conditions likely to

make the equipment susceptible to e problem, and identify any common-mode

initiators that may exist. GE Nucle Energy personnel, associated with GE's

Switchgear Apparatus Service Shop in A anta, Georgia, have informed the NRC

that GE is developing a modification for he RMS-9 circuitry to correct the

problem. GE also explained that its evidene suggests that ungrounded and/or

delta-connected (grounded or ungrounded) systms are most susceptible to the

kind of transients to which the RMS-9s can sp iously respond. GE is

currently assisting Maine Yankee in exchanging t least temporarily) RMS-9- equipped breakers for ones fitted with EC-type se *es overloads.

Meanwhile, the incidents of spurious tripping, although isolated, raise

the concern that a common-mode initiator of ground fai ts such as a loss-of- coolant accident or high-energy line break could conce ably cause propagation

of short-duration, high-current transients to multiple p itlons of an

electrical distribution system which could result in spurnus tripping of

RMS-9-equipped breakers and the attendant loss of vital loa, possibly in

more than one train. This information notice requires no spe ific action or

written response. If you have any questions about the informa on in this

notice, please contact one of the technical contacts listed bela or the

appropriate Office of Nuclear Reactor Regulation (NRR) Project Ma ger.

Brian K. Grimes, Director

Division of Operating Reactor Support

Office of Nuclear Reactor Regulation

Technical contacts: Stephen D. Alexander, NRR (301) 504-2995 Kamalakar R. Naidu, NRR (301) 504-2981 Attachment: List of Recently Issued NRC Information Notices

• See previous concurrence

OFFICE VIB/DRIL VIB/DRIL BC RIL TECHED

NAME SALEXANDER* KNAIDU* A --AV M DGABLE*

DATE 8/05/93 8/05/93 //938/ 6 /93 8/06/93 COPY YES YES YES YES NO NO

OFFICE D/ L/NRR BC/SELB/DEST BC/OGCB/DORS D/DORS

NAME C CBERLINGER GMARCUS BKGRIMES

DATE 8/( /93 8/ /93 8/ /93 /93 COPY YES NO YES NO YES NO YES NO YES NO

UII-ILIAL ------ Idler.

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OFFICIAL RECORD LUPY UUUMLN I NANL: WZ)VIK1FPAN

IN 93-XX

August XX, 1993 and Control in ainville, Connecticut) providing trip units that are less

sensitive to high mplitude, short-duration current transients. However, the

NRC has learned tha certain early versions of the RMS-9 units had

instantaneous trip fu tions that could not be bypassed or the time delay

adjusted indicating als a potential misapplication problem.

The NRC is attempti to obtain sufficient information to better define

the range of applications o these units, envelope the conditions likely to

make the equipment susceptibl to the problem, and identify any common mode

initiators that may exist. GE uclear Energy personnel associated with GE's

Atlanta, Georgia, Switchgear App atus Service Shop have informed the NRC that

GE is developing a modification fo the RMS-9 circuitry to correct the

problem. GE also explained that its vidence suggests that ungrounded and/or

delta-connected (grounded or ungrounde systems are most susceptible to the

kind of transients to which the RMS-9s n spuriously respond. GE is also

currently assisting Maine Yankee in excha ing (at least temporarily) RMS-9- equipped breakers for ones fitted with EC tye series overloads.

Meanwhile, the incidents of spurious tiping, although isolated, raise

the concern that a common-mode initiator of gr nd faults such as a loss-of- coolant accident or high-energy line break coul conceivably cause propagation

of short-duration, high-current transients to mul tile portions of an

electrical distribution system which could result i spurious tripping of

RMS-9-equipped breakers and the attendant loss of vit 1 loads, possibly in

more than one train.

This information notice requires no specific actio or written response.

If you have any questions about the information in this n ice, please contact

one of the technical contacts listed below or the appropria Office of

Nuclear Reactor Regulation (NRR) Project Manager.

Brian K. Grimes, Director

Division of Operating Reactor Support

Office of Nuclear Reactor Regulation

Technical contacts: Kamalakar R. Naidu, NRR (301) 504-2981 Stephen D. Alexander, NRR (301) 504-2995 Attachment: List of Recently Issued NRC Information Notices

OFFICE VIB/DRIL VIB/DRIL SC/VIB/DRIL BC/VIB/DRIL TECHED

NAME KNAIDU SALEXANDER GCWALINA LNORRHOLM

8/ /93 8/ /93 8/ /93 8/ /93 8/6 /93 DATE

COPY YES YES YES YES NO NO

OFFICE D/DRIL/NRR BC/SELB/DEST BC/OGCB/DORS D/DORSl

NAME CEROSSI CBERLINGER GMARCUS BKGRIMES

DATE 8/ /93 8/ /93 8/ /93 8/ /93 /93 YES NO YES NO YES NO YES NO YES NO

COPY

IN 93-XX

August XX, 1993 and Control in ainville, Connecticut) providing trip units that are less

sensitive to high mplitude, short-duration current transients. However, the

NRC has learned tha certain early versions of the RMS-9 units had

instantaneous trip funtions that could not be bypassed or the time delay

adjusted indicating als a potential misapplication problem.

The NRC is attempt g to obtain sufficient information to better define

the range of applications these units, envelope the conditions likely to

make the equipment susceptib e to the problem, and identify any common mode

initiators that may exist. G Nuclear Energy personnel associated with GE's

Atlanta, Georgia, Switchgear Aplaratus Service Shop have informed the NRC that

GE is developing a modification r the RMS-9 circuitry to correct the

problem. GE also explained that i evidence suggests that ungrounded and/or

delta-connected (grounded or ungroun ed) systems are most susceptible to the

kind of transients to which the RMS-9:can spuriously respond. GE is also

currently assisting Maine Yankee in exc anging (at least temporarily) RMS-9- equipped breakers for ones fitted with E type series overloads.

Meanwhile, the incidents of spurious tripping, although isolated, raise

the concern that a common-mode initiator o round faults such as a loss-of- coolant accident or high-energy line break c ld conceivably cause propagation

of short-duration, high-current transients to ultiple portions of an

electrical distribution system which could resu t in spurious tripping of

RMS-9-equipped breakers and the attendant loss o vital loads, possibly in

more than one train.

This information notice requires no specific ction or written response.

If you have any questions about the information in t is notice, please contact

one of the technical contacts listed below or the app priate Office of

Nuclear Reactor Regulation (NRR) Project Manager.

1//

Brian K. Grimes, Director

Division of Operating Reactor Support

Office of Nuclear Reactor Regulation

Technical contacts: Kamalakar R. Naidu, NRR (301) 504-2981 Stephen D. Alexander, NRR (301) 504-2995 Attachment: List of Recently Issued NRC Information Notices

OFFICE IB IL lVIB/DRIL , SC/VIB/DRIL BC/VIB/DRIL TECHED

NAME KNAW A o- SALEXANDER GCWALINA LNORRHOLM

DATE 8/6&/93 8/ /93 8/ /93 8/ /93 COPY YES YES YES YES NO NO

OFFICE D/DRIL/NRR BC/SELB/DEST BC/OGCB/DORS D/DORS

NAME CEROSSI CBERLINGER GMARCUS BKGRIMES

DATE 8/ /93 8/ /93 8/ /93 8/ /93 /93 COPY YES NO YES NO YES NO YES NO YES NO