IE Circular 77-16, Emergency Diesel Generator Electrical Trip Lock-out Features
CR77016
UNITED STATES
NUCLEAR REGULATORY COMMISSION
WASHINGTON, D. C. 20555
December 9, 1977
MEMORANDUM FOR: B. H. Grier, Director, Region I
J. P. O'Reilly, Director, Region II
J. G. Keppler, Director, Region III
E. M. Howard, Director, Region IV
R. H. Engelken, Director, Region V
FROM: H. D. Thornburg, Director, Division of Reactor
Operations Inspection, IE
SUBJECT: IE CIRCULAR 77-16, EMERGENCY DIESEL GENERATOR ELECTRICAL TRIP LOCK-OUT FEATURES
The subject document is transmitted for issuance on December 13, 1977. The
Circular should be issued to all holders of Reactor Operating Licenses and
Construction Permits. Also enclosed is a draft copy of the transmittal
letter.
Harold D. Thornburg, Director
Division of Reactor Operations
Inspection
Office of Inspection and
Enforcement
Enclosures:
1. Circular 77-16
2. Draft Transmittal Letter
CONTACT: V. D. Thomas, IE
49-28180
.
Transmittal letter for Circular 77-16, to each holder of an NRC Operating
License and Construction Permit.
Addressee:
The enclosed Circular 77-16, is forwarded to you for information. If there
are any questions related to your understanding of the suggested actions,
please contact this office.
Signature
(Regional Director)
Enclosure:
IE Circular 77-16
.
NUCLEAR REGULATORY COMMISSION
OFFICE OF INSPECTION AND ENFORCEMENT
WASHINGTON, D.C. 20555
December 9, 1977
IE Circular 77-16
EMERGENCY DIESEL GENERATOR ELECTRICAL TRIP LOCK-OUT FEATURES
Description of Circumstances:
On June 15, 1977, Duquesne Light Company (Beaver Valley 1) reported that
during the performance of a test of the diesel-generator (D/G) trip lock-out
features in the emergency mode of operation, the D/G output circuit breaker
opened when the field voltage trip interlock was tested. This is contrary to
a requirement for this facility that, in the emergency mode, all D/G output
breaker trips except generator differential and overcurrent be automatically
disabled. The engine overspeed trip, which shuts down the diesel engine (but
does not affect breaker operation) is also expected to be operable during
the emergency mode of operation.
An investigation conducted by the licensee disclosed that the unexpected
opening of the output breaker was due to deenergizing a field voltage
sensing relay which was supplied by the vendor but had not been disconnected
during the on-site acceptance testing of the D/G nor disabled by the
protection circuitry logic. A redundant field voltage relay which was
supplied by the licensee is correctly by-passed during fast start conditions
and emergency operation.
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IE Circular 77-16 December 9, 1977
A design change was initiated by the licensee which removed the field
voltage trip feature. This was accomplished by disconnecting the set of
relay contacts to the trip circuitry of the D/G output breaker. Subsequent
testing of the D/G was performed by the licensee which demonstrated
satisfactory operation.
This is an example of an event which resulted from inadequate test procedure
performance. The procedures as performed had not previously identified the
type of deficiency described in this circular.
The safety significance of this situation is that the premodified protection
circuitry would have opened the circuit breaker if a loss of field voltage
occurred while running in the emergency mode of operation.
The D/G Units for the above facility were supplied by the Electro Motive
Division (EMD) of General Motors. The model numbers for the D/G Units are:
Engine Model No. 20-645-E4
Generator Model No. A-20-C2
Control Panel Model No. 999-20
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IE Circular 77-16 December 9, 1977
All holders of operating licenses or construction permits should assure that
the appropriate D/G protection trip circuits are provided with automatic
by-pass features that prevent them from negating automatic starting or
tripping of D/Gs during fast start or emergency operations. It is
recommended that the following be considered in your reviews of this matter:
1. Facility procedures should specifically determine whether the
protection circuitry that trips the D/G set or the associated output
breaker is in accordance with the facility Technical Specifications.
2. Test procedures for your D/G sets (e.g. acceptance preoperational and
surveillance tests) should be reviewed to assure that D/G system
performance is demonstrated by these tests to be in accordance with
related operational requirements specified in the facility Technical
Specifications.
3. Strengthening of management controls should be reviewed as necessary to
assure adherence to D/G test procedures by plant personnel.
No written response to this circular is required. If you require additional
information regarding this matter, contact the Director of the appropriate
NRC Regional Office.
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