Information Notice 1993-91, Misadjustment Between General Electric 4.16-kV Circuit Breakers & Their Associated Cubicles
UNITED STATES
NUCLEAR REGULATORY COMMISSION
OFFICE OF NUCLEAR REACTOR REGULATION
WASHINGTON, D.C. 20555
December 3, 1993 NRC INFORMATION NOTICE 93-91: MISADJUSTMENT BETWEEN GENERAL ELECTRIC 4.16-KY
CIRCUIT BREAKERS AND THEIR ASSOCIATED CUBICLES
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 multiple common-cause failures
of logic functions due to misadjustment between General Electric (GE) 4.16-kv
Magne-Blast circuit breakers and their associated cubicles. It is expected
that recipients will review the information for applicability to their
facilities and considei 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
During surveillance testing at the Duane Arnold Energy Center on
September 16, 1993, the "B" standby diesel generator output breaker (1A411) to
essential bus 1A4 failed to close after simulation of a loss of offsite power
(LOOP) and loss of coolant accident (LOCA) signal. During normal plant
operation, the normally closed feeder breaker (1A402)
from the startup
transformer and the normally open feeder breaker (1A401) from the standby
transformer provide essential bus 1A4 with two offsite sources of power. One
of the "b"
contacts (closed when the breaker is open) from each offsite power
feeder breaker stationary auxiliary switch (mounted in the breaker cubicle) is
used in the diesel generator output breaker automatic close-permissive circuit
to indicate whether the two offsite power feeder breakers are open or closed.
A closed indication from either breaker 1A401 or IA402 will prevent the diesel
generator output breaker from closing automatically (unsynchronized) onto
essential bus 1A4.
Breakers 1A401, IA402, and IA411 are GE Magne-Blast types.
Troubleshooting revealed that the auto-closing logic for the diesel generator
output breaker was not being completed because a lb" contact from breaker
IA401 was open, indicating that the breaker was closed when the breaker was
actually open. When the breaker 1A401 is open and in its fully elevated
operating position in the cubicle, there is supposed to be a small gap or
clearance between the breaker plunger and the stationary auxiliary switch
9311190456 PtR
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KAIN 93-91 December 3, 1993 operating rod (see Attachment 1, Figure 2) to ensure positive closure of all
lb" contacts in the stationary auxiliary switch. However, the plunger of
breaker IA401 was found to be actually pushing its stationary auxiliary switch
operating rod up about 4.8 mm [3/16 inch] with the breaker open. This
apparently occurred when the breaker was last elevated into its operating
position which then opened one or more lb' contacts (including the one in the
diesel generator breaker control circuit) from their normally closed position.
The misalignment rendered the "B* diesel generator inoperable from
July 21, 1993, to September 25, 1993, because it was not capable of
automatically closing onto the 1A4 bus.
Upon investigation, the licensee determined that it had performed routine
preventive maintenance on breaker IA401 (a vertically racking, GE model
AM-4.16-350-2H) on July 21, 1993, which consisted essentially of lowering the
breaker to the bottom of the cubicle, inspecting and lubricating it, and
cycling the breaker after elevating it to its test position. However, cycling
the breaker in the test position does not operate the stationary auxiliary
switch unless a special test link is fitted. Therefore, this action alone
does not verify the various control functions performed by the stationary
auxiliary switch contacts. The wB" diesel generator monthly tests were
completed satisfactorily during the operating cycle, but these tests use a
synchronized manual closure of the diesel generator output breaker, which
bypasses the breaker automatic close permissive (dead bus) circuit.
Even
though the once-per-operating-cycle integrated LOOP/LOCA test detected the
failure, the potential existed for the "B" diesel generator to be inoperable
for an entire operating cycle, or when required during an outage. The
periodic routine preventive maintenance performed on breaker IA401, which may
have resulted in the breaker misadjustment and opening of a stationary
auxiliary switch contact, was not scheduled in conjunction with a surveillance
test (such as the integrated LOOP/LOCA test) that would verify proper
operation of the auxiliary switch contacts.
Discussion
Misadjustment between the stationary auxiliary switch and the breaker plunger
on 4.16-kv breakers has the potential to cause multiple common-cause failures
of many different logic functions that rely on these auxiliary switch
contacts. The circuit breaker plunger to auxiliary switch operating rod
adjustment may be affected by breaker maintenance, switchgear maintenance, differences in operating plunger height of interchangeable breakers, differences in breaker cubicles and breaker position switches, and non- repeatability in breaker height when racking in breakers.
During breaker maintenance on July 21, 1993, the licensee for the Duane Arnold
plant checked and adjusted the height between the breaker lifting rail and the
operating plunger in accordance with the applicable GE breaker technical
manual (GEK-7320F, Revision 2/80, 'Magne-Blast Circuit Breakers Types AM-4.16-
350-2C and -2H"). However, the licensee did not verify the open breaker
plunger-to-operating-rod clearance of 0 to 3.2 mm [O to 1/8 inch] as
recommended in the applicable GE switchgear technical manual (GEH-1802,
"Instructions - Metal-Clad Switchgear Types M26 and M36 for Magne-Blast
-
v
VIN 93-91 December 3, 1993 Circuit Breakers Types AM-4.16 and AM-13.8"). In order to ensure a minimum
gap for positive 3b' contact closure, the manufacturer (now called the GE
Specialty Breaker product department) provided additional guidance in its
Service Advice Letter (SAL) 073-323.1, issued February 1, 1978, specifying a
gap of 1.6 mm [1/16 inch] to 3.2 mm (1/8 inch]. This SAL also provides the
recommended sequence of adjustments.
Further conversations between the licensee and GE determined that there are
additional dimensional checks (not contained in either the breaker or
switchgear technical manual) which would provide additional assurance of
proper auxiliary contact operation after breaker maintenance. These
additional dimensional checks for a closed breaker (see Attachment 1, Figure 1) are:
7.9 +/- 1.6 mm [5/16 +/- 1/16 inch] from the top of the circuit breaker
plunger nut to the bottom of the auxiliary switch operating rod casing.
All law contacts are closed with at least 23.8 mm [15/16 inch] travel of
the operating rod.
NOTE:
Total specified travel of the plunger is 27 +/- 1.6 mm
[1 1/16 +/- 1/16 inch]. If the total plunger travel is set at
the minimum specified value of 25.4 mm [1 inch] and the
plunger-to-operating-rod gap is set at the maximum specified
value of 3.2 mm [1/8 inch], the amount of travel of the
operating rod would only be 22.2 mm [7/8 inch], or less than
the required 23.8 mm [15/16 inch] necessary to fully ensure
closure of the Oa" auxiliary contacts when the breaker
closes.
For an open breaker (see Attachment 1, Figure 2) the additional dimensional
check is:
The operating rod collar should rest on the operating rod casing, and
the operating rod should not be displaced by the plunger of an open
breaker.
GE stated that it will issue a SAL to clarify the instructions and dimensions
contained in the previous publications. Meanwhile, licensee inquiries on this
subject may be directed to GE Nuclear Energy Power Delivery Services in
King of Prussia, Pennsylvania (Phone: 215-992-6049/Fax: 215-992-6191.)
Related Generic Communications
NRC Information Notice 91-55, *Failures Caused by an Improperly Adjusted
Test Link in 4.16 KV General Electric Switchgear, dated
September 16, 1991.
IN 93-91 December 3, 1993 No specific action or written response is required by this information notice.
If you have any questions regarding this matter, please contact one of the
technical contacts listed below or the appropriate Office of
clear Reactor
Regulation (NRR) project manager.
e
Brian K. Grimes, Director
Division of Operating Reactor Support
Office of Nuclear Reactor Regulation
Technical contacts: Jay A. Hopkins, RIII
(319) 851-5111
David S. Butler, RIII
(708) 790-5796
Stephen D. Alexander, NRR
(301) 504-2995 Attachments:
1. Magne-Blast Circuit Breaker Plunger and
Stationary Auxiliary Switch Adjustments
2. List of Recently Issued NRC Information Notices
Attachment 1
,V~ xIN 93-91 Decembr 3, 1993 MAGNE-BLAST CIRCUIT BREAKER PLUNGER - STATIONARY
AUXILIARY SWITCH ADJUSTMENTS (ADAPTED FROM GE
MVSD FIELD INSTALLATION DRAWING 0172C7558)
(Not to Scale)
a, (MINIMUM TRAVEL
"116'J
TO ENSURE ALL
"A"
CONTACT
S
L
'CLOSE
I
SWITCH
OPERATING'
GAP:
I
0-NO"PER GE-1802 PER SAL. 073-323.1
1 [To
WITH BREAKER OPEN:
MINIMUM GAP
TO ENSURE ALL "By
CONTACT
S CLOSED
MAXIMUM GAP
TO ENSURE FULL
SWITCH ROD
TRAVEL FOR
"A"
CONTACT
CLOSURE WHEN
BREAKER CLOSES
SET BY ADDING OR
REMOVING PWNGER
SHIMS (WASHERS)
i
Figure 1
BREAKER CLOSED
Figure 2
BREAKER OPEN
At^,thment 2 IN 93-91
December 3, 1993
Page 1 of I
LIST OF RECENTLY ISSUED
NRC INFORMATION NOTICES
Information
Date of
Notice No.
Subject
Issuance
Issued to
93-90
93-89
93-88
93-87
Unisolatable Reactor
Coolant System Leak
Following Repeated
Applications of Leak
Sealant
Potential Problems with
BWR Level Instrumentation
Backfill Modifications
Status of Motor-Operated
Valve Performance Pre- diction Program by the
Electric Power Research
Institute
Fuse Problems with
Westinghouse 7300
Printed Circuit Cards
Identification of Iso- topes in the Production
and Shipment of Byproduct
Material at Non-power
Reactors
Problems with X-Relays
in D8- and DHB-Type
Circuit Breakers Manu- factured by Westinghouse
Determination of Westing- house Reactor Coolant
Pump Seal Failure
Potential Loss of Spent
Fuel Pool Cooling
Following A Loss of
Coolant Accident (LOCA)
12/01/93
11/26/93
11/30/93
11/04/93
10/29/93
10/20/93
10/20/93
10/07/93 Al 1 for
holders
nuclear
power reactors.
All holders of OLs or CPs
for nuclear power reactors.
All holders of OLs or CPs
for boiling water reactors.
93-85
All holders of OLs or CPs
for nuclear power reactors.
All holders of OLs or CPs
for test and research
reactors.
All holders of OLs or CPs
for nuclear power reactors.
All holders of OLs or CPs
for pressurized water
reactors (PWRs).
All holders of OLs or CPs
for boiling water reactors
(BWRs).
93-84
93-83 OL = Operating License
CP - Construction Permit
-'-' IN 93-91 December 3, 1993 No specific action or written response is required by this information notice.
If you have any questions regarding this matter, please contact one of the
technical contacts listed below or the appropriate Office of Nuclear Reactor
Regulation (NRR) project manager.
orig /s/'d by BKGrimes
Brian K. Grimes, Director
Division of Operating Reactor Support
Office of Nuclear Reactor Regulation
Technical contacts:
Jay A. Hopkins, RIII
(319) 851-5111 David
(708)
S. Butler, RIII
790-5796
Stephen D. Alexander, NRR
(301) 504-2995 Attachments:
1. Magne-Blast Circuit Breaker Plunger and
Stationary Auxiliary Switch Adjustments
2. List of Recently Issued NRC Information Notices
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IN 93-xx
November xx, 1993
No specific action or written response is required by this information notice.
If you have any questions regarding this matter, 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:
Jay A. Hopkins, RIII
(319) 851-5111
David S. Butler, RIII
(708) 790-5796
Stephen D. Alexander, NRR
(301) 504-2995 Attachments:
1. Magne-Blast Circuit Breaker Plunger and Stationary Auxiliary
Switch Adjustments
2. List of Recently Issued NRC Information Notices
- SEE PREVIOUS CONCURRENCE
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IN 93-xx
November xx, 1993
No specific action or written response is required by this information notice.
If you have any questions regarding this matter, 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:
Jay A. Hopkins, RIII
(319) 851-5111
David S. Butler, RIII
(708) 790-5796
Stephen D. Alexander, NRR
(301) 504-2995 Attachments:
1. -1
4h16 Circuit Breaker Plunger and Stationary Auxiliary
Switch Operating-Red- Adjustments
2.
List of Recently Issued NRC Information Notices
- SEE PREVIOUS CONCURRENCE
OFFICE
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IN 93-xx
November xx, 1993
No specific action or written response is required by this information notice.
If you have any questions regarding this matter, 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:
Jay A. Hopkins, RIII
(319) 851-5111
David S. Butler, RIII
(708) 790-5796
Stephen D. Alexander, NRR
(301) 504-2995 Attachments:
1. Magne-Blast Circuit Breaker Plunger and Stationary Auxiliary
Switch Adjustments
2.
List of Recently Issued NRC Information Notices
- SEE PREVIOUS CONCURRENCE
OFFICE
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Closed Circuit Breaker Operating Plunger and Auxiliary Switch Mechanism
Operating Rod Configuration
2.
Open Circuit Breaker Operating Plunger and Auxiliary Switch Mechanism
Operating Rod Configuration
3.
List of Recently Issued NRC Information Notices
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