View source for Information Notice 1992-63, Cracked Insulators in Asl Dry Type Transformers Manufactured by Westinghouse Electric Corporation

{{Adams
| number = ML031200032
| issue date = 08/26/1992
| title = Cracked Insulators in Asl Dry Type Transformers Manufactured by Westinghouse Electric Corporation
| author name = Rossi C
| author affiliation = NRC/NRR
| addressee name = 
| addressee affiliation = 
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| license number = 
| contact person = 
| document report number = IN-92-063, NUDOCS 9208200177
| document type = NRC Information Notice
| page count = 5
}}
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UNITED STATES

NUCLEAR REGULATORY COMMISSION

OFFICE OF NUCLEAR REACTOR REGULATION

WASHINGTON, D.C. 20555 August 26, 1992 NRC INFORMATION NOTICE 92-63:    CRACKED INSULATORS IN ASL DRY TYPE

TRANSFORMERS MANUFACTURED BY: WESTINGHOUSE I

ELECTRIC CORPORATION

*92 AUG 31 P3 :51

==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 problems that could result from the cracking of

ceramic insulators on ASL Dry Type Power Center 4160/480 volt (V) 3-phase

transformers manufactured by the Westinghouse Electric Corporation

(Westinghouse). It is expected that recipients will review the information

for applicability to their facilities and consider 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==
On May 13, 1991, the Washington Public Power Supply System (WPPSS), the

construction permit holder for the Washington Nuclear Project, Unit 3, (WNP-3)
reported to the NRC that cracks were observed on ceramic insulators that

support the high voltage coils in certain Class 1E and Non-Class 1E 4160/480 V

transformers rated at 1000 and 1500 kVA.

The Pacific Gas and Electric Company (PG&E), the licensee for the Diablo

Canyon Nuclear Power Plant, Units 1 and 2,-found a hairline crack on an

insulator in one of the 4160/480V, 1000 KVA rated transformers in Unit 2. In

a letter of August 30, 1991, Westinghouse, the supplier of the transformer, recommended that PG&E replace the cracked insulator as soon as possible. On

September 19, 1991, PG&E evaluated the operability to justify continued

operation with the hairline crack on one of its insulators.

Discussion

The design of these transformers typically'-includes a magnetic.iron core, three high voltage coil assemblies and a steel frame.' The high voltage coil

assemblies are held in position and are electrically separated from the ground

plane of the transformer by a set of insulators uniformly spaced around the

top and bottom periphery of each coil assembly. In turn, the insulators are

9208200177 AtE

o- // C-      It Icc

IN 92-63 August 26, 1992 held in place by pressure rings. A compressive force is applied to the top of

each pressure ring by four jack bolts. The assembly is designed to maintain

the spatial relationship of the coils, insulators, and the pressure ring

during normal operation, a seismic event, or an electrical fault condition.

The 1000 kVA transformer has six insulators at the top and bottom of each high

voltage coil assembly while the 1500 kVA transformer has eight. The

insulators are 4 3/8 inches long and 1 inch in diameter. The center portion

of each insulator has a series of annular indentations that form five rings or

skirts. Typically, the cracks were found in these indentations.

At WNP-3, both the WPPSS and NRC staff observed that some of the cracked

insulators in the affected transformers were installed off-center and were not

perpendicular to the pressure ring.        The cracks were on insulators located at

the top or bottom of the high voltage coils and at least one hairline crack

was observed along the smallest cross section in the upper half of each

affected insulator.

On November 14, 1991, Westinghouse informed the NRC (Attachment 1) that it had

sent a customer notification letter to all utilities that may have received

Westinghouse safety-related ASL Dry Type transformers. Westinghouse stated

that it had received information from the ABB Power Transmission and

Distribution Company, Incorporated, that the cracking of the insulators could

have a catastrophic effect on the structural integrity of the transformer.

This information notice requires no specific action or written response. If

you have any questions about the information in this-notice, please contact

the technical contact listed below or the appropriate Office of Nuclear

Reactor Regulation (NRR) project manager.

~Kha'rs` CE.Rossi, Directof

Division of Operational Events Assessment

Office of Nuclear Reactor Regulation

Technical contact:    K. R. Naidu, NRR

(301) 504-2980
Attachments:
1. Westinghouse, letter ET-NRC-91-3638
2. List of Recently Issued NRC Information Notices

a ; A , -  -             .  t.         ..............................................................

.              ,
* I       ,

Attachment 1 IN 92-63 August 26, 1992 -Nuclear and Alvancea

Westinghouse                 Energy Systems                                     Tennciogy Division

Electric Corporation                                                            Box           vii

B0x s3                           *.

3ttsturgn Pennsylvania 1523C 3i:
                                                                                      ET-NRC-9 1-3638 November 14, 1991 Doc=en~t Contro! Desk

US Nuclear Regulatory Commission

Washington, DC 20555 Attention: Dr. Thomas E. Murley, Director

Office of Nuclear Reactor Regulation

Dear Dr. Murley:
      Attached is a generic version of the customer notification letter, issued by Westinghouse to all utilities, both domestic and international which may have been supplied with safety related ASL Dry Tpe

Transformers. This letter was prepared to document Westinghouse's evaluation, of the ASL Dry Type

Transformer issue, pursuant to the requirements of 1OCFR Part 21.

S. R. Tritch, Manager

Engineering Technology Department

LRH/sa

Attachment

cc: ABB Power T&D Company Inc.

651 Holiday Drive

Pittsburgh, PA 15220
           Attn: P. J. Pillitteri, Field Service Manager Integrated Logistics Support

LrrfuwkEr.NzsC4-3632 F ElR AlDOCK     0301)0397

Attachment 1 IN 92-63 August 26, 1992 --
Subject:  Westinghouse ASL Dry Type Transformers

To: Utility

On June 10, 199i the Washington Public Power Supply System (WPPSS)
notified the NRC of a potential deficiency regarding ASL Power Center Dry

Type Transformers. In September 1987, an insulator that supports the

C-phase coil of a Westinghouse supplied dry type air ventilated 2000KVA

Non Class IE transformer was discovered to be cracked at WNP-3. In

January 1990, three additional cracked insulators were discovered in

another Non Class IE transformer purchased under the same contract.

Due to the above, WNP-3 engineering personnel inspected the plant's six

Class IE power center transformers purchased under the same contract.

These transformers, which have not yet been energized, were inspected in

November 1990. This inspection revealed cracked insulators  in two of the

six transformers.

Westinghouse sold the.transformer product lines, including the ASL Dry

Type Power Center Transformers, to ABB Power Transmission and Distribution

Company Inc. Consequently, Westinghouse does not have the necessary

technical information or expertise available to identify all of the

potentially affected plants, the cause, nor the ultimate solution.

Westinghouse has been informed by ABB that the cracking of the insulators

could have catastrophic effect on the structural integrity of the

transformer. If your plant was supplied or utilizes the ASL Power Center

Dry TyDe Transformer, Westinghouse recommends that you pursue this matter

directly with ABB. Westinghouse has provided a copy of this generic

notification to ABB and the NRC and has concluded its evaluation of this

issue pursuant to the requirements of 1OCFR Part 21.

===Project Manager===
/sa

: -S

Attachment 2 IN 92-63 August 26, 1992 LIST OF RECENTLY ISSUED

NRC INFORMATION NOTICES

Information                                   Date of

Notice No.             Subject                Issuance   Issued to

92-62          Emergency Response             08/24/92   All U.S. Nuclear Regulatory

Information Require-                      Commission licensees.

ments for Radioactive

Material Shipments

92-61          Loss of High Head              08/20/92   All holders of OLs or CPs

Safety Injection                          for nuclear power reactors.

92-60          Valve Stem Failure             08/20/92   All holders of OLs or CPs

Caused by Embrittlement                   for pressurized water

reactors (PWRs).

92-59          Horizontally-Installed         08/18/92   All holders of OLs or CPs

Motor-Operated Gate                       for nuclear power reactors.

Valves

-58          Uranium Hexafluoride           08/12/92   All Fuel Cycle Licensees.

Cylinders - Deviations

in Coupling Welds

92-57          Radial Cracking of             08/11/92   All holders of OLs or CPs

Shroud Support Access                     for boiling water reactors

Hole Cover Welds                          (BWRs).

92-56          Counterfeit Valves in          08/06/92   All holders of OLs or CPs

the Commercial Grade                      for nuclear power reactors.

Supply System

92-55          Current Fire Endurance         07/27/92   All holders of OLs or CPs

Test Results for                          for nuclear power reactors.

Thermo-Lag Fire Barrier

Material

92-54          Level Instrumentation          07/24/92   All holders of OLs or CPs

Inaccuracies Caused by                    for nuclear power reactors.

Rapid Depressurization

92-53          Potential Failure of           07/29/92   All holders of OLs or CPs

Emergency Diesel Gen-                     for nuclear power reactors.

erators due to Ex- cessive Rate of Loading

OL = Operating License

CP = Construction Permit}}

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