United States Nuclear Regulatory Commission - Protecting People and the Environment

Information Notice No. 84-84, Revision 1: Deficiencies in Ferro-Resonant Transformers

                                                           SSINS No.:6835  
                                                           IN 84-84, Rev. 1 

                               UNITED STATES 
                       NUCLEAR REGULATORY COMMISSION 
                    OFFICE OF INSPECTION AND ENFORCEMENT 
                           WASHINGTON, D.C. 20555 

                               April 24, 1985 

Information Notice No. 84-84 REVISION 1:  DEFICIENCIES IN FERRO-RESONANT 
                                             TRANSFORMERS 

Addressees: 

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

Purpose: 

This information notice revision provides new information regarding the 
capacitor terminations used in General Electric ferro-resonant transformers 
utilized in Westinghouse vital 7.5 kVA inverters. 

This information notice is provided as a notification of two potentially 
significant deficiencies pertaining to ferro-resonant transformers 
manufactured by General Electric Company (GE). Such transformers have been 
used by Westinghouse Electric Corporation (Westinghouse) as integral 
components of vital 7.5 kVA inverters. In addition, similar deficiencies may
exist on 30 and 45 kVA inverters utilizing similar but larger ferro-resonant
transformers. Westinghouse has provided such inverters to several utilities 
for non-safety related applications such as supplying power to computers. It
is expected that recipients will review the 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: 

The subject ferro-resonant transformers produce a simulated ac signal from 
either an ac or dc source; the inverters provide instrumentation power to 
both protection and control systems of nuclear power facilities. 

Westinghouse recently informed the Nuclear Regulatory Commission (NRC) of 
two deficiencies involving the subject ferro-resonant transformers. In 
addition, Westinghouse identified its utility customers known to have 
received inverters with suspect transformers and stated that these customers 
had been informed of the issue. Westinghouse also stated that it was 
possible that other utilities could be affected by these issues; therefore, 
this notice is being issued to ensure that all affected utilities are aware 
of the potential deficiencies. 



8504220347 
.

                                                        IN 84-84, Rev. 1  
                                                        April 24, 1985    
                                                        Page 2 of 3       

First Deficiency: 

By letter dated September 14, 1984, Westinghouse informed the NRC of the 
first of two deficiencies involving the subject ferro-resonant transformers.
This deficiency was discovered by Westinghouse during its long-term aging 
program, and reportedly occurred at the manufacturer's plant in 1977, at 
which time the capacitor terminals had been changed from "ring-tongue" to 
"fast-on" terminal connections. It is our understanding that GE made these 
changes concurrent with changing the capacitors from a polychlorinated 
biphenyl (PCB) design to a non-PCB design. Since all capacitors may not have
been changed to a non-PCB design, this notice also informs the addressees 
that their facilities may be using ferro-resonant transformers with 
capacitors containing PCB. 

Westinghouse described its concern with the capacitor fast-on terminations 
in its September 14, 1984, letter as follows: 

     Each capacitor terminal has three connection points--two fast-on 
     lugs and one solder lug. The capacitor wire terminations are 
     fast-on style as well. For the two transformers in the Westinghouse 
     test program, some wire terminations had incorrectly been forced 
     on the solder lugs. Were this connection to fall off due to a 
     seismic event, the most severe consequence would be a detuning of 
     the transformer, increased harmonic distortion and reduced output 
     (from 118 volts to as low as 60 volts). This decreased voltage 
     could both increase the error of instrumentation powered by this 
     inverter and could potentially cause an indeterminant number of 
     relays in both the protection and control systems to drop out due 
     to the reduced voltage. 

Westinghouse issued a technical bulletin (Attachment 1) to facilities 
potentially having capacitors with incorrect terminations. This attachment 
describes the potential problem and provides instructions for proper 
connection of the capacitors. However, because facilities other than those 
listed may be using inverters with suspect ferro-resonant transformers, a 
copy of the Westinghouse technical bulletin is attached, thereby assuring 
that affected plants are aware of the deficiency and Westinghouse's 
recommendations. 

Westinghouse's initial technical bulletin discussing this issue, 
NSD-TB-84-08 (Attachment 1), recommended a 20 pound pull test to confirm 
connector make-up.  Westinghouse recently informed the NRC that a pull test 
minimum of 5 pounds force, rather than the initially recommended value of 20 
pounds, would provide conservative margin for the seismic requirements of 
the terminal connections.  Westinghouse has provided this information to its
customers by NSID-TB-84-08, Addendum A.  A copy of this addendum is attached
to the initial technical bulletin as an integral part of Attachment 1. 
.

                                                        IN 84-84, Rev. 1  
                                                        April 24, 1985    
                                                        Page 3 of 3       

Second Deficiency:  

By letter dated September 26, 1984, Westinghouse informed the NRC of the 
second deficiency involving the subject ferro-resonant transformers. 
Westinghouse was informed of this deficiency by Comanche Peak where three 
separate transformers failed shortly after they were initially electrically 
loaded. The failed units were returned to the manufacturer, GE, for 
evaluation. The determination made by GE was that the affected transformer 
reactors were inadequately secured, thereby allowing the center leg to shift
and vibrate while energized. The vibration, in turn, caused an insulation 
breakdown. 

The Westinghouse letter of September 26 indicates that if a transformer were
to short to ground, the inverter would continue to try to supply the load 
resulting in a collapsing output voltage (e.g. , 60-65 volts was noted at 
Comanche Peak). GE has determined that if the transformer has been under 
load for six months, the magnetic forces applied would have caused a failure 
if the manufacturing defect were initially present. 

Westinghouse has issued a technical bulletin (Attachment 2) to facilities 
potentially having transformers with loose reactor legs. This attachment 
describes the potential problem and provides recommended corrective actions 
for the suspected defect. However, because facilities other than those 
listed in Attachment 2 may be using inverters with the above described 
defects, a copy of the Westinghouse technical bulletin is attached, thereby 
ensuring that affected plants are aware of the deficiency and Westinghouse's
recommendations. 

No specific action or written response is required by this information 
notice; however, if you have any question regarding this notice, please 
contact the Regional Administrator of the appropriate NRC Regional Office or
the technical contact listed below. 



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

Technical Contact: I. Villalva, IE 
                   (301) 492-9006 

Attachments: 
1.   Westinghouse Technical Bulletin No. NSD-TB-84-08 
       and NSID-TB-84-08, Addendum A 
2.   Westinghouse Technical Bulletin No. NSID-TB-84-11 
3.   List of Recently Issued IE Information Notices 
Page Last Reviewed/Updated Tuesday, November 12, 2013