ML13339A768

Letter from Tom Homer Notification of Part 21 Report on a CR7 Diode Wiring Reversed on the Automatic Voltage Regular (AVR) Panels for Palo Verde

ML13339A768
Person / Time
Site:	Palo Verde
Issue date:	11/13/2013
From:	Homer T Engine Systems
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
10CFR21-0110, Rev 0
Download: ML13339A768 (7)

Text

11-13-13;11:33AM; # 1/ 7 ENGINE SYSTEMS, INC.

nESI) 175 Freight Road Rocky Mount, NC 27804 Telephone: 2521977-2720 Fax: 252/446-1134 TELEFAX Date: November 13, 2013 Company: NRC Operations Center Fax Number: 301/816-6151 Verification No.: 301/816-5100

Reference:

Report No. 10CFR21-0110, Rev. 0 From: Tom Homer Page: 1 of 7

Dear Sir:

Following this cover is a copy of our report 10CFR21-0110, Rev. 0, for a 10CFR21 reportable notification on a CR7 diode wiring reversed on the automatic voltage regulator (AVR) panels for APS-Palo Verde, part number D72-12200-1 00-PVNGS.

A copy of this report will be mailed to the NRC Document Control Desk and to our affected nuclear customer.

Should you have questions, please let us know.

Sincerely, ENGINE SYSTEMS, INC.

Tom Homer Quality Assurance Manager Quality Performance With Pride

11-13-13;11 :33AM; # 2/ 7 (SI ENGINE SYSTEMS, INC.

175 Freight Road, Rocky Mount, NC 27804 Telephone: 252/977-2720 Fax: 2521446-1134 Report No. 10CFR21-0110 Rev. 0: 11/12/13 10CFR21 REPORTING OF DEFECTS AND NON-COMPLIANCE COMPONENT: CR7 diode wiring reversed AVR panels for APS-Palo Verde P/N: D72-12200-100-PVNGS SYSTEM: Emergency Diesel Generator (APS-Palo Verde)

CONCLUSION: Reportable in Accordance With 10CFR21 Prepared By: Date: ///_/ZA8 Engineering Manager Reviewed By: Date: 11-12-1%,

Quality Assurance Manager Quality Performance With Pride

11-13-13;11:33AM; # 3/ 7 Report No. 10CFR21-01 10 Record of RevisiDns Page: 1 of 1 REV DATE PAGE DESCRIPTION 0 11/12/13 Initial issue.

11-13-13;11:33AM; # 4/ 7 Report No. 10CFR21-0110 Revision: 0 Date: 11/12/13 Page: 1 of 4 Component:

Diode CR7 wiring reversed: AVR panel P/N D72-12200-1 00-PVNGS Summary:

Engine Systems Inc. (ESI) began a 10CFR21 evaluation on 10/25/2013 after receiving notification from APS-Palo Verde Nuclear Generating Station that diode CR7 on their automatic voltage regulator (AVR) panels had the wiring connections reversed. During installation of the AVA panels, generator output voltage buildup was observed to be longer than expected during fast start testing.

The slow voltage buildup was determined to be caused by a lack of generator field flashing.

Troubleshooting revealed that the field flash diode CR7 wiring was reversed.

The evaluation was concluded on 11/11/2013 and it was determined that this issue is a reportable defect as defined by 10CFR21. The incorrect wiring of diode CR7 prevents field flashing of the generator. Lack of generator field flashing can result in failure of generator voltage buildup, or excessive voltage buildup time, during starting of the emergency diesel generator (EDG). This condition could therefore have impacted operability of the EDG and prevented it from performing its safety related function.

Discussion:

The AVR panel, part number D72-12200-100-PVNGS, is part of the overall static excitation system for the Palo Verde EDGs. Diode CR7 is wired in series with the field flash resistor and a normally open contact from the field flash contactor (FFC) to the generator field (F+) connection. This circuit is only active during startup of the EDG as the generator field is flashed (via an external 125 VDC supply) to initiate generator voltage buildup. CR7 conducts in the forward direction during field flashing to excite the generator field and it prevents reverse current flow when the exciter output begins to increase as the generator comes up to nominal voltage. An electrical schematic of the field flash circuitry is shown below in Figure 1.

Figure 1 - Generator Field Flash Schematic

11-13-13;11:33AM; # 5/ 7 Report No. 100FR21-0110 Revision: 0 Date: 11/12/13 Page: 2 of 4 APS-Palo Verde determined during installation testing of the AVR panel that the CR7 diode was installed incorrectly; specifically, the wiring to the anode and cathode was reversed. The CR7 diode assembly consists of a standard power diode (where the mounting stud is the cathode and the terminal end is the anode) mounted on a heat sink. With the diode mounted to the heat sink via the diode stud, the heat sink becomes the diode cathode. A screw installed in the heat sink provides a mounting stud for the CR7 cathode wiring connection(s). The diode anode is wired to another stud at the other end of the heat sink; this stud is electrically isolated from the heat sink and is utilized for the CR7 anode wiring connection(s). Location of CR7 on the AVR panel is shown below in Figure 2.

Figure 2 - AVR Panel Component Layout

11-13-13;11:33AM; # 6/ 7 Report No. 10CFR21-0110 Revision: 0 Date: 11/12/13 Page: 3 of 4 Root cause evaluation:

The AVR panel layout drawing (8000654-01) conflicts with the AVR panel electrical schematic and wiring diagram. The layout drawing has CR7 oriented such that the anode connection is on the top and the cathode connection is on the bottom; both the electrical schematic (8000654-02) and the wiring diagram (8000654-11) show the CR7 anode wiring as the "bottom" and the cathode wiring as the "top". With the layout showing the anode at the top, the CR7 wiring was installed reversed.

Functional test procedure 8000654-FTP-1 for the AVR panel verified operation of the field flash contactor FF but did not include checks to verity proper installation of diode CR7. The pre-operational tests of ESI field test procedure 8001720-TP should have discovered the reversed CR7 connections because it required verification of field flash voltage at AVR terminals TS3(F+) and TS3(F-); apparently these steps were not performed or were not performed correctly during the installation process.

Evaluation of previous shipments:

Drawings for AVR panels supplied previously by ESI have been reviewed and the CR7 diode wiring has been verified to be correct. The CR7 reversed wiring condition only applies to the AVR panels (PIN D72-12200-100-PVNGS) shipped to Palo Verde.

Affected Customers; APS-Palo Verde is the only affected customer. This reversed CR7 wiring condition only applies to the five (5) AVR panels (P/N D72-12200-1 00-PVNGS) shipped to Palo Verde on ESI sales order 8001720 (4 panels shipped in May 2013 and 1 panel shipped in June 2013).

11-13-13;11:33AM; # 7/ 7 Report No. 10CFR21 -0110 Revision; 0 Date: 11/12/13 Page: 4of4 Corrective Action:

Diode assembly CR7 shall be removed from the AVR subpanel, rotated 180 degrees and re-installed using the same mounting holes and mounting hardware. The existing panel wiring to CR7 shall then be connected in the same physical location, thereby connecting wire F+ to the cathode and wire F7 to the anode as shown in the photographs below. This shall be performed on all five (5) AVR panels shipped to APS-Palo Verde (reference ESI sales order 8001720).

wire F+wire F+

cathode wire ..- .7...

CR7 Diode Assembly- Not Correct CR7 Diode Assembly - Correct (as-shipped) (rotated 180-)

To prevent recurrence of this issue, the following is being implemented:

o AVR panel layout drawing 8000654-01 has been revised to rotate diode CR7 180 degrees.

This will change the anode connection from the top to the bottom orientation.

o The AVR panel factory test procedure 8000654-FTP-1 has been revised to include steps to verify proper connection of diode CR7 within the field flash circuitry.