ML20085M602

RO 50-267/75/13A:on 750911,fan Start Relay for 480-volt Transformer 1B Failed.Caused by Component Failure & Design Flaw.Relays Replaced W/Better Application & Relay Logic Circuitry Reversed to Require Deenergized Relay

ML20085M602
Person / Time
Site:	Fort Saint Vrain
Issue date:	10/13/1975
From:	Hillyard H, Lambert D, Swart F PUBLIC SERVICE CO. OF COLORADO
To:	Howard E NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV)
Shared Package
ML20085M605	List: ML20085M602 ML20085M607
References
RO-50-267-75-13, NUDOCS 8311090044
Download: ML20085M602 (4)

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• n pubHe Service Company *2 CoHomde P. O. Box 361, Platteville, Colorado 80651 L Li\i

/ J October 13, 1975 Mr. E. Morris Howard, Director Nuclear Regulatory Commission m 4, is %[af- ",;pi . g Region IV Office of Inspection and Enforccment

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Suite 1000 h' - '

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c' Arlington, Texas 76012 '

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'67]kT FEF: Facility Operating License " -

No. DPR-34 Docket No. 50-267 IE FILE COPY;

Dear Mr. Howard:

Enclosed please find a copy of Unusual Event Report No. 50-267/75/13A, Final, submitted per the requirements of the Technical Specifications.

This report is being issued in order to correct a minor omission in the

" Identification of Occurrence" given in Unusual Event Report No. 50-267/

75/13.

Very truly yours, _

h 66o -

N<a s Frederic E. Swart Superintendent, Nuclear Production Fort St. Vrain Nuclear Generating Station FES/alk cc: Mr. Roger S. Boyd

/

e311090044 751013 /

PDR ADOCK 05000267 g PDR ,"

COPY SENT REGION _

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. . 9s . 1 REPORT DATE: October 13. 1975 UNUSUAL EVENT 75/13A Page 1 of 3 OCCURRENCE DATE: September 11 2 1975 70RT ST. VRAIN NUCLEAR CENERATING STATION PUBLIC SERVICE COMPANY OF COLORADO P.O. Box 361

• PLATTEVILLE, COLORADO 80651 REPORT NO. 50-267/75/13A Final IDENTIFICATION OF

_0CCURRENCE:

Failure of the fan start relay for 480 V Transformer 1B. This is identified as an Unusual Event per Section 7.6 paragraph C(3) of the Technical Specifications.

CONDITIONS PRIOR

_TO OCCURRENCE: Steady State Power Routine Shutdown ~

Hot Shutdown Routine Load Change Cold Shutdown X Other (specify) -

Refueling Shutdown ' ' None specified because conditions Routine Startup varied and did not contribute to the failure the major plant parameters at the time of the event were as follows:

Power RTR

• Eth ELECT

• We .

Secondary Coolant Pressure

• psig f Temperature *

• F Flow

• f/hr.

Primary Coolant Pressure

• psig Temperature * *

• F Core Inlet

• F Core Outlet Flow

• f/hr.

• Not listed since they have no bearing on problem.

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' a. . . . .-.~_ _ . _.

= , . . .._...a.. . . . .

t: ,

i UNUSUAL EVENT 75/13 A .

. . . .' Page 2 of 3

• DESCRIPTION OF . '

OCCURRENCE:

On 8/27/75, it was reported by the plant operating personnel thaton460 either automatically V high transformer 1B cooling fans failed to start, Operations temperature, or by manual operation of fan start hand switch.

personnel determined by local indication that the cooling fans w  ;

requirements.

In order to prevent damage due to overheating, it was necessary f.

The fans returned to ,

to replace the fan start relay on an emergency basis.

normal operation with replacement of the relay.

[

APPARENT CAUSE Unusual Service Cond.

' X Design _

Including Environ.

OF OCCURRENCE: l X Component Failure Manufacture "Other (specify)

InstallationIConst.

Operator 9

Procedure .

ANALYSIS OF .

OCCURRENCE:

From Athissearch search of it wasessential 480a V noted that transformer history existed ofmaintenance trouble with thisrecords particularwas cond control.

. an analysis and test'of the fan control scheme was completed.

On September 11, 1975,

• The results of this study were that the control scheme was unsatisfactory in three .

~

respects:

We type relay used to actuate the cooling fans had a tendency to hang

~

- 1) up with slight changes in orientation.

2)

%e start circuit relay logic was undesirable in that it was necessary to energize the relay to start the fans.

3)

Failure of the fans to start on high transformer temperature was not alarmed in the control room. .

. CORRECTIVE ACTION:

For the five air cooled 480 V transformers (3 essential and 2 non .

1) ne'unsuitabic relays will be repinced with a better application.

7 ,

o _

o UNUSUAL EVENT 75/13A Page 3 of 3

2) The relay logic circuitry will be reverned so that it requires a de-energized relay to start the cooling fans.

3) An alarm on high temperature will be installed in the control room.

4) The local handswitches will be rewired to bypaan the fan start relay and start the fans directly.

Thenc corrective actionn have aircady been completed for 480 V Transformer 18.

FAlt.URE DATA / SIMII.AR REPORTED OCCURPINCES:

None <

PROGRAMMATIC IMPACT:

None EDP. IMPACT:

Nonc '. ,

.. A Submitted by: ,

kJ hr Harvey W. (tillyard', J h.

Technical Services Supervisor Reviewed by: A - M (~ /Mut 4 Duane L. Lambert V f Supervisor, Denvor Plant Electriciana Approved by:

f/ '

W A.v? % . . wh ;i rederic E. Swart

[ Superintendent, Nuclear Production e

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