ML17339A574

Forwards LER 78-017/03L-0

ML17339A574
Person / Time
Site:	Saint Lucie, Turkey Point
Issue date:	06/13/1978
From:	Schmidt A FLORIDA POWER & LIGHT CO.
To:	James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML17207A819	List: ML17207A818 ML17339A563 ML17339A565 ML17339A567 ML17339A569 ML17339A571 ML17339A572 ML17339A574 ML17339A575 ML17339A576 ML17339A577
References
NUDOCS 8002150499
Download: ML17339A574 (6)

Text

Reference 13 j.

FLORIO% POWER 5 UGHT COMPAt4Y June 13, 1978 PAN-LI-78-154 i~a. James P. O'Reilly, Director, Region II

..Office of Inspection and Enforcement U. S. Nuclear Regulatory Commission 230 Peachtree Street, N. N., Suite 1217 Atlanta, Georgia 30303 Mr. O'Reilly:

'ear REPORTABLE OCCURRENCE 335-78-17 ST. LUCIE UNIT 1 DATE OF OCCURRENCE: MAY 14,'978 OFF-SITE POWER The attached Licensee Event Report is being submitted in accordance with Technical Specification 6.9 to provide 30-day. notificat'on of the subject occurrence.

Very truly yours, A. D. Schmidt Vice President Power Resources.

MAS/ms Attachment CC Harold F. Reis, Esquire Director,:Office of Inspection and Enforcement (30)

Director, Office of Management Information and Program Control (3)

PEOPLE... SERVING PEOPLE

n J

.REPORTABLE OCCURRENCE 335-78-17 LXCENSEE EVENT REPORT ATTACtLitENT PAGE 1 INTRODUCTION Florida Power s Light Co. (FPW experienced an electrical power system disturbance on .Sunday, ttay 14, 1978, which resulted in the loss of power to an area of the PPL system This blacked .out area included the loss of. off-site power 'to St Lucie Plant for approximately 8 minutes I ~

Pault recorder'ecords, the Hest Palm Beach computer printout, and logs were used. to reconstruct the sequence of events C.

PRE-DXSTORBMCE CONOXTXONS . ~

Only conditions in affected area are listeR=

St. Lucie Plant unit No 1 off for refueling

~ 2 Pxatt 8 Hhitney 240kV ring bus open (240G36835 open) pxior to switching.' This mitch had been previously reported to be arcing The Dispatcher believed the switch to st:1'be inoperative

~ -

3 Two 240/138kV autotxansfoxmexs (49-1035 8 49-1168) at Tlidway Substation vere recently instal'led 'to replace smaller capacity units.

DISTURBANCE ~ ~

On Sunday, .Nay 14,. 1978, a approximately 7:45AM wnile switching out the Pxatt 6 5~hitney-Ranch 240~V circuit for a routine clearance, a condition was-created on.the Pxatt *.Hhitney south 240kV bus that caused lightning arxestexs on this bus to'ail destructively Hot ionized gas from the lightning axxesters caused a "C" phase to gxound fau3t on the Nidway-Ranch 240kV cixcuit which pass s directly over tne Pxatt R Hhitney bus.

'I At Nidway Substation improper connection of the relay current polarizing ciicuit resulted in incorrect operation of the Directional Carrier Ground Relays (CZPG) on the.Nalabar-Aidway 240kV No. 1, Nalabax-Midway 240kV No 2 and the Nidway-Plumosus 138kV circuits Erroneous current polarizing like-resulted in failuxe to trip by the ground relays of the Midway terminal 'ise of the faulted Nidway-Ranch 240kV circuit. Pailure of this terminal to trip resuLted in a back-up operation of the autotxansformer tertiaxy relay at.

Nidway Substation The Hartman-Midway and Okeechobee-Midway lines then tripped, interrupting service to St'. Lucie and other stations., On-site power was supplied at St Lucie by automatic diesel generator operation. St Lucie remained on diesel power until after system conditions stabilized.

'EPORTABLE OCCURRENCE 335-78-17 LICENSEE EVENT REPORT ATTACR!KNT PAGE 2 For given phase to ground fault, th'e north autot ansfoxmer tertiary relay is

. more sensitive than the south autotransfoxmer tertiary relay.

This accounts Sox the operation of only, the north autotransformer tertiary relay The two main contributing factors to the power loss were=

1 Xmproper switching at Pxatt 8 Wu.tney Substation 2 Xmpxoper connect:ion of both 240/138kV autotransfomer polarizing CT circuits at Hidway Substation.

I RESTORE XOH ~

SeveraL attempts wexe made to energize the north bus at Hidway Substation via the Halabax 240kV Mo. 2 circuit. Ho~ever, the lockout relay previously. trip-

ped by the tertiary xelay had not been reset The south bus aC Hidway Sub-station was energized via .the .Ranch 240kV circuit As switching continued to normalize the system, a breaker at Pratt I Whitney

~

was closed and the original lightning arrester pxoblem was recreated This resulted in the deenergizing of -Hidway Substation Pinal xeenexgization of Hidway Substation and St. Lucie Plan~ vas accomplished by the closing of the Pa.".ch 240kV circuit: at 7:53:30 h

This resulted .in. the loss of off-site powex to St .Lucia Plant for approximately eight minutes and sixteen and one-half seconds.'witching was then carried out until the entixe affected. area, was returned to normal with the exception o Hie~way Substation's north autotransfoxm r CORRECTIVE ACTXONS 1 The improper polarizing at Hidway Substation has b en corrected 2 - The north and south buses at Pxatt 5 Whitney Substation have been tied

. together to avoid the bus high voltage problem encountered during switching Drawings jn use at the time wexe reviewed ~d an error was detected As a result of this, Syst;em Protection Hemorazuhm No 3.10.1-A titled "The Connection of CT'.s Xn An Autotxansfoxmer bhen Used, As a Source For Gxounct.

. Po3.arizing Circuit" was issued Hay 22, 1978. This memorandum out3ines the racedures for checking transformer nameplate data against FPL drawings as well as the elect:rical tests which axe to b made. This memorandum vi3.3. be incorporated into the Power. Supply Pxocedures Hanual and vill prevent a reoccurence of this event 4 System Operators and Dispatchers have been advised o. the hazards of an ungrounded delta

0

@is 0