United States Nuclear Regulatory Commission - Protecting People and the Environment

Information Notice No. 85-82: Diesel Generator Differential Protection Relay Not Seismically Qualified

                                                        SSINS No.:  6835
                                                            IN 85-82 

                               UNITED STATES 
                           WASHINGTON, D.C. 20555 

                             October 18, 1985  

                                   RELAY NOT SEISMICALLY QUALIFIED  

All nuclear power reactor facilities holding an operating license (OL) or a 
construction permit (CP). 


This information notice is provided to alert licensees of a potentially sig-
nificant safety problem involving a General Electric (GE) Model 12CFD relay 
that is not seismically qualified for Class IE service when in the de-ener-
gized state of operation. The relay is used for protection of an emergency 
diesel generator (EDG) against phase-to-phase or phase-to-ground electrical 
faults (shorts) by both boiling water reactor (BWR) and pressurized water 
reactor (PWR) nuclear power generating stations. 

It is suggested that recipients review this information for applicability to
their facilities and consider actions, if appropriate, to preclude similar 
problems occurring at their facilities. However, suggestions contained in 
this information notice do not constitute NRC requirements; therefore, no 
specific action or written response is required. 

Description of Circumstances: 

Licensees of BWR and PWR nuclear generating stations have reported using a 
high-speed differential protection relay that has been declared by the manu-
facturer to be not seismically qualified for the service intended. The 
relay, GE Model 12CFD, which is being used for emergency diesel generator 
protection against electrical shorts and grounds at the generator output, 
has not been seismically qualified to operate in the de-energized state for 
this application. Generally, the relay operates in the de-energized position 
before EDG operation. However, it then operates in the energized position 
whenever the EDG provides an electrical output to essential Class IE 
components. The safety concern of this issue involves an inadvertent 
activation of the normally de-energized relay from a seismic event. 
Momentary activation of the relay, in the circuits examined, blocks the 
automatic start feature of the EDG during certain emergency plant conditions 
through operation of another relay in the system. 


                                                          IN 85-82 
                                                          October 18, 1985 
                                                          Page 2 of 3 

On June 17, 1985, Kewaunee Nuclear Power Generating Station notified the NRC
that the high-speed differential relay being used for diesel generator pro-
tection at their plant did not meet the seismic requirements for that appli-
cation when the relay was in the de-energized mode. Kewaunee had discovered 
that the relay, GE 12CFD series, had earlier failed to meet seismic require-
ments under similar circumstances at the Arkansas Unit 1 Nuclear Generating 
Station in November 1981. The short term corrective measure taken by Kewaun-
een to resolve the issue was to defeat the relay trip function. The long 
term corrective measures are currently under review. 

At Palisades, while finalizing the environmental qualification plan for the 
diesel generator control panel, the licensee discovered that the GE high-
speed differential relays specified by design drawings would not meet the 
seismic requirements for the service intended at that plant when the relay 
was in the de-energized mode. The relay was identified as GE Model 12CFD and
was being used in an application similar to that at the Kewaunee plant 
above. The licensee of Palisade's has since replaced all deficient relays 
with relays seismically qualified for service in all modes of operation. 


An event occurred at Arkansas Unit 1 plant on November 19, 1981, when the 
plant was operating at 90% of full power. An alarm sounded alerting opera-
tions personnel that the generator lockout relay, associated with the 
plant's No. 1 EDG, had tripped. The licensee's investigation of this 
occurred revealed that the "C" Phase differential relay (one relay is used 
for each phase of the three-phase system) had activated and caused a 
generator lockout relay to trip even though the affected EDG was not 
operating at the time. A walk through by persons in the EDG area revealed 
that the EDG exiter cubicle, which houses the differential relays, may have 
been opened and reclosed with sufficient force to cause spurious operation 
of the differential relay, GE Model 12CFD. Subsequent investigation by the 
licensee concluded that the relay did not meet the minimum seismic 
qualifications in that plant's design when the EDG is in the standby mode 
and, the relay is in a de-energized state. A similar problem was identified 
with the same make and model differential relays at both Brunswick Unit 2 
and at Salem Unit 1 in early 1982. 

Arkansas Unit 1, Brunswick Unit 2, and Salem Unit 1 have since replaced the 
deficient relays with a relay that GE considers more suitable and 
seismically qualified for the application discussed above. 

The NRC review of the above problems concluded that the relays should be 
seismically qualified in their energized and-de-energized states, to pre-
clude their spurious activation during a seismic event. Additionally, review
of GE's GER 3069 report, "Relay Protection of Class IE Systems," shows that 
the 12CFD differential relays were successfully tested for 3.5 g in the 
energized modes and only 0.75 g in the de-energized mode. The calculated 
required g-level capacity, including the effects of floor response, for this
equipment at 


                                                          IN 85-82 
                                                          October 18, 1985 
                                                          Page 3 of 3 

Arkansas Unit 1 exceeded the qualified g level of the 12CFD relay in the 
de-energized mode by a factor of about three. Review of GE s GER 3069 report
also revealed that GE type IJD differential relays do meet seismic require-
ments in all modes of operation mentioned above and is the GE recommendation
for replacement of the differential relay in question. 

No specific action or written response is required by this information 
notice. If you have any questions about this matter, please contact the 
Regional Administrator of the appropriate regional office or this office. 

                                   Edward L. Jordan, Director 
                                   Division of Emergency Preparedness 
                                     and Engineering Response 
                                   Office of Inspection and Enforcement 

Technical Contact:  Vincent D. Thomas 

Attachment:  List of Recently Issued IE Information Notices 
Page Last Reviewed/Updated Friday, May 22, 2015