United States Nuclear Regulatory Commission - Protecting People and the Environment

Information Notice No. 88-14: Potential Problems with Electrical Relays

                                  UNITED STATES
                          NUCLEAR REGULATORY COMMISSION
                      OFFICE OF NUCLEAR REACTOR REGULATION 
                             WASHINGTON, D.C.  20555

                                 April 18, 1988


Information Notice No. 88-14:  POTENTIAL PROBLEMS WITH ELECTRICAL RELAYS


Addressees: 

All holders of operating licenses or construction permits for nuclear power 
reactors. 

Purpose: 

This information notice is being provided to alert recipients to potential 
problems involving HFA, PVD 21B, PVD 21D, and HGA relays manufactured by 
General Electric Company (GE), as described below.  Although some of these 
problems are several years old, they are included because utilities are still 
identifying problems discovered while implementing advice issued by GE in the 
early 1980s.  The specific problem with the HFA relays concerns mechanical 
binding in the relay caused by incorrect location of a stop tab that is welded 
to the armature.  The problems with the PVD 21B, PVD 21D, and HGA concern 
their seismic capability.  It is expected that licensees will review this 
information for applicability to their facilities and consider actions, as 
appropriate, to avoid similar problems.  However, suggestions contained in 
this information notice do not constitute NRC requirements; therefore, no 
specific action or written response is required.  

Description of Circumstances:

a.   HFA Relays

     In June 1986, Duane Arnold Energy Center reported that HFA relays were 
     not resetting.  GE determined, after investigation, that mechanical 
     binding in the relays prevented the normally closed contacts from making 
     contact when the relays were de-energized.  This was caused by the 
     incorrect location of a stop tab that is welded to the armature.  The 
     incorrect location, combined with possible movement of the magnetic 
     assembly, causes the armature binding.  In July 1986, TVA experienced 
     similar problems.  

     On July 21, 1986, the GE Meter and Control Business Division (MCBD), 
     Malvern, Pennsylvania, issued a 10 CFR Part 21 report to the NRC.  On 
     November 14, 1986, MCBD issued Service Advice Letter (SAL) 188.1, which 
     instructed recipients to test the relay to identify and correct improper 
     operation.  The SAL stated that MCBD could not determine when the stop 
     tab problem had begun, but that relays manufactured between January 1983 
     and October 1986 were suspect.  Date codes were provided that could be 
     

8804110009
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     used to identify potentially affected relays.  However, on June 5, 1987, 
     Pilgrim implemented SAL 188.1 and identified several improperly operating 
     relays which were manufactured outside the suspected date codes.  

     In view of this, all HFA relays may be suspect.  Additionally, the NRC 
     recently issued NRC Bulletin 88-03, "Inadequate Latch Engagement in HFA 
     Type Latching Relays Manufactured by General Electric (GE) Company," 
     March 10, 1988, regarding problems from inadequate latch engagement.  
     
b.   PVD 21B and PVD 21D Relays (see Attachment 1)

     In 1977, GE listed the seismic capability of the normally open contacts 
     of the PVD 21B and PVD 21D differential relays as 6g zero period 
     acceleration (ZPA) with the relay energized and the contacts closed.  The 
     tripping of each of these relays in response to differential over current 
     is by a "low set" voltage unit, device 87L, and a "high set" current 
     unit, device 87H.  Device 87L is an instantaneous voltage unit that has 
     its coil connected across the dc terminals of a full wave rectifier 
     device.  Device 87L has two sets of normally open contacts, one of which 
     is connected in parallel with the contacts of the seal-in unit.  Device 
     87H is an instantaneous overcurrent unit, with its coil connected in 
     series with thyrite discs; it has a single set of normally open contacts.  

     Originally, GE published data which implied that the seismic capability 
     of 6g ZPA applied equally to both 87H and 87L functions.  In 1983, GE 
     revised the seismic capabilities as follows:  the capability of the 87L 
     function remained at 6g ZPA, and the capability of the 87H function was 
     reduced to 2g ZPA.  GE stated that the 87H set of normally open contacts 
     is generally wired in parallel with both the open 87L contacts and the 
     open 87L seal-in contacts when the PVD relay is used to trip a circuit 
     breaker.  GE stated that the 87H function of the PVD is less sensitive 
     than the 87L function (it requires more operating signal).  As a result, 
     opening the normally open 87H contacts for a time greater than 2 milli-
     seconds as a consequence of a seismic event between 2g and 6g ZPA should 
     not interfere with tripping the circuit breaker because the parallel 87L 
     contact would remain closed up to 6g ZPA.  In view of the 2g ZPA seismic 
     capability of the 87H contact, GE recommended the application be checked 
     if the 87H contacts are used separately for any functions other than 
     tripping.  

c.   HGA Relays (see Attachment 1)

     During a re-evaluation of qualification data for relays used in nuclear 
     Class 1E systems, MCBD determined that the seismic data for HGA 11 and 
     HGA 111 relays published in MIL No. RS77-3, dated March 25, 1977, were in 
     error.  The incorrect data were revised in MIL No. 82-12, dated July 26, 
     1982.  Specifically, MIL No. RS77-3 listed the seismic capability of the 
     normally closed contacts of ac-rated HGA 11 or HGA 111 
     
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     relays at 1.0g ZPA when the relays were in the de-energized state.  The 
     dc-rated relays were listed at 1.5g ZPA for the same condition.  The re-
     vised seismic capability of the normally closed contacts of both ac and 
     dc HGA 11 and HGA 111 relays in the de-energized state is less than 0.5g 
     ZPA.  

     GE has conducted studies to determine design changes that could improve 
     the seismic capability of the normally closed contacts when the relay is 
     de-energized.  Additionally, a separate study considered the seismic 
     capability of alternate HGA relay models as a means for improving the 
     seismic capability of normally closed contacts with the relay 
     de-energized.  At this time, GE has no plans for development of an HGA 
     relay with improved seismic capability.

     On the basis of the above information, GE recommends that Class 1E cir-
     cuits using normally closed contacts of HGA 11 and HGA 111 relays, with 
     the relay de-energized, be evaluated for the effect on the entire circuit 
     of an HGA 11 or HGA 111 contact opening longer than 2 milliseconds. 

     On June 24, 1987, Duane Arnold reported to the NRC (1) that, based on the 
     revised data, HGA 11 relays providing critical functions in the core 
     spray, low pressure coolant injection, high pressure coolant injection, 
     and reactor core isolation cooling systems at Duane Arnold have 
     indeterminate qualification, and (2) that the relays were being replaced. 

Discussion:

a.   HFA Relays

     For HFA relays, in addition to SAL 188.1, GE issued the following SALs:

     (1)  SAL 139.2, dated April 28, 1976.  This SAL superseded SAL 139.1, 
          dated September 5, 1973.  

     (2)  SAL 152.1, dated April 28, 1976. 

     (3)  SAL 152.2, dated November 3, 1980.

     (4)  SAL 152.2A, dated March 12, 1982.

     (5)  SAL 169.1, dated May 28, 1982.

b.   PVD 21 Relays

     For PVD 21 relays, GE issued SAL 174.1 dated April 11, 1983.  This SAL 
     provided clarification of the seismic capability of the 87H and 87L 
     contacts.  

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Most plants using PVD and HGA style relays are subject to the verification of 
seismic adequacy of mechanical and electrical equipment under Unresolved 
Safety Issue (USI) A-46 (as outlined in Generic Letter 87-02).  However, PVD 
and HGA style relays have also been found in newer plants that are not subject 
to Generic Letter 87-02 (e.g., Susquehanna Unit 2 LER 86-024-000).  

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




                              Charles E. Rossi, Director
                              Division of Operational Events Assessment
                              Office of Nuclear Reactor Regulation


Technical Contact:  K. R. Naidu, NRR
                    (301) 492-0980


Attachments:
1.  General Electric Letter to NRC
      dated February 24, 1983
2.  List of Recently Issued NRC Information Notices
.                                                            Attachment 2
                                                            IN 88-14
                                                            April 18, 1988
                                                            Page 1 of 1

                             LIST OF RECENTLY ISSUED
                            NRC INFORMATION NOTICES 
_____________________________________________________________________________
Information                                  Date of 
Notice No._____Subject_______________________Issuance_______Issued to________

88-13          Water Hammer and Possible     4/18/88        All holders of OLs
               Piping Damage Caused by                      or CPs for nuclear
               Misapplication of Kerotest                   power reactors. 
               Packless Metal Diaphragm 
               Globe Valves 

88-12          Overgreasing of Electric      4/12/88        All holders of OLs
               Motor Bearings                               or CPs for nuclear
                                                            power reactors. 

88-11          Potential Loss of Motor       4/7/88         All holders of OLs
               Control Center and/or                        or CPs for nuclear
               Switchboard Function Due                     power reactors. 
               to Faulty Tie Bolts 

88-10          Materials Licensees:  Lack    3/28/88        All NRC licensees 
               of Management Controls Over                  authorized to use 
               Licensed Programs                            byproduct 
material. 

87-44,         Thimble Tube Thinning in      3/28/88        All holders of OLs
Supp. 1        Westinghouse Reactors                        or CPs for nuclear
                                                            power reactors 
                                                            that employ a 
                                                            Westinghouse NSSS.

88-09          Reduced Reliability of        3/18/88        All holders of OLs
               Steam-Driven Auxiliary                       or CPs for nuclear
               Feedwater Pumps Caused                       power reactors. 
               by Instability of Woodward 
               PG-PL Governors 

88-08          Chemical Reactions with       3/14/88        All NRC licensees 
               Radioactive Waste                            generating or pro-
               Solidification Agents                        cessing low level 
                                                            radioactive waste.
_____________________________________________________________________________
OL = Operating License
CP = Construction Permit 
Page Last Reviewed/Updated Tuesday, November 12, 2013