Information Notice 1993-75, Spurious Tripping of Low-Voltage Power Circuit Breakers with GE RMS-9 Digital Trip Units
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
Attachment
In 93-75 September
17 1993 Page I of I LIST OF RECENTLY ISSUED NRC INFORNATION
NOTICES Informatlon
Date Ot Notice No. Subject Issuance Issued to 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 KRC licensees.
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 Inspections
93-71 Fire at Chernobyl
Unit 2 09/13/93 All holders of OLs or CPs for nuclear power reactors.;
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, Loss of Flow from the 08/23/93 All holders of OLs or CPs Supp. 2 Residual Heat Removal for nuclear power reactors.Pump during Refueling Cavity Draindown 93-67 Bursting of High 08/16/93 All holders of OLs or CPs Pressure Coolant for nuclear power reactors.Injection
Steam Line Rupture Discs Injures Plant Personnel OL -Operating
License CP
- Construction
Permit a 49) 0, IB 3 U 4C f* faf 2 z Q otu to a cco 2o 0 V f 0 C*)i"-J e 41 h °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 COPY YES YES YES YES NO 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 COPY YES YES YES NO YES NO YES NO--. --- t nRARMflT WAMP. 01-7r, IN OFFILIAL KLLUKU UUrl UUUV% 1'Ln 1 nr I.., -. ....
\~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--. v flnv-I MlRIT AMRF. aG7C TM OFFICIAL KtLUKU LurY WuV%,I'LII
I IANrLc.v;. -Io F .L 1 IN 93-XX September
XX, 1993 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 IE 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 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 8/11/93 8/06/93 COPY YES YES YES YES NO OFFICE D/DRIL/NRR
BC/SELB/DEST
BC/OGCB/DORS
D/DORS____l
NAME CEROSSI* CBERLINGER*
GMARCUS9 BKGRIMES DATE 8/13/93 8/13/93 /93 9/ /93 / /93 COPY YES YES YES ____-YES NO YES NO v nntrIlMFNT
IWAMV iRM I1P1N OFFICIAL KLLUKU LUFY uuvu% lW l a, ..A>, .<S ENS......
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 OFFICE D/DRIL/NRR
BC/SELB/DEST
BPRt_ D/DORSi NAME CEROSSI* CBERLINGER*
k7! ARCUS BKGRIMES DATE 8/13/93 8/13/93 __ /_938/ /93 I/93l COP Y YESE _ YS nYES NO YES NO r~n,'mmIirikir
kiAur. nuenTOTD ThM OFFICIAL RECKR LUPY WUtUMEM I n14nc1 .-n%1l1. 7 n o Ar .A II
IN 93-XX August XX, 199:. 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 3*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 _8_ _93 e_ 8/ /93 /_/93 COPY YES YES YES NO YES NO YES NO.rf nr#nArkeT
MAuC. QMCQTDTD TN OFFIIAL McUKU LuVY wuuVLqcn I 11MI-I.FM1Q1 W I 1% LIs .air9 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 NAME SALEXANDER*
KNAIDU* G L OA _ O LM DGABLE*DATE 8/05/93 8/05/93 8/1 /93 8/l/93 8/06/93 COPY YES YES YES YES NO NO OFFICE D/DRUIER,.
BC/SELB/D
0 BC/OGCB/DORS
D/DORSl NAME C ACBERLINGEV
GMARCUS BKGRIMES DATE 8/1,393 8/L5/93 8/ /93 llCOPY YES NO YES NO YES NO YES NO YES NO rhrINAEUT
LAMC. OMCOTDTD TN OFFICIAL RECORD COPY UUuVrLcr1 I 11PULc.rvlloJ7Ir
.GoLI d I
K- -, 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
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
-L--T-rlL:
Idler. 1uc4TnT 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
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 DATE 8/ /93 8/ /93 8/ /93 8/ /93 8/6 /93 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 COPY YES NO YES NO YES NO YES NO YES NO
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
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