ML18127A838

Preliminary Report on System Disturbance, May 16, 1977

ML18127A838
Person / Time
Site:	Turkey Point
Issue date:	05/20/1977
From:	Florida Power & Light Co
To:
References
Download: ML18127A838 (16)

Text

P R EL IMI NARY REPORT 0 N SYSTEM DISTURBANCE MAY 16, 1977 FLOR I DA POWER 5 L I GHT COMPANY MAY 20, 1977

TABLE OF CONTENTS PAGE Introduction Surrmary Description of Disturbance Loss of Turkey Point Unit 3 Loss of the Ft. Myers - Ranch 240kV Line Initial Service Restoration Loss of the Andytown - Orange River 500kV Line Service Restoration System Conditions Figure 1 - Map of Area Affected - Loss of Turkey Point 3 and Ft. Myers - Ranch 240kV Line Figure 2 - Area Loads and Generation Figure 3 - Area Loads and Generation Figure 4 - Net Unit Capabilities at 10:08 AM Figure 5 - Summary of Relay and Breaker Operations 10 Figure 6 - Sequence of Events 12 Figure 7 - Area Loads and Generation 13 Figure 8 - Hap of Area Affected - Loss of Orange River 500kV Line

INTRODUCTION Florida Power 5 Light Company experienced a major outage on May 16, 1977, that extended from Ft. Pierce southward along the East Coast to the Florida Keys'igh speed oscillograph records, recording charts, and other data have been examined in order to reconstruct the sequence of events that occurred.

This report documents the initial analysis. In-depth analysis will be done to determine specific cause and effect of the operations given in this report.

SUMMARY

The outage was triggered at 10:24 a.m. when the heavily loaded Ft. Myers - Ranch 240kY line tripped due to a phase-to-ground fault.

The east and south areas of the system immediately became separated from the north and west areas when three 240kV and seven 138kV lines relayed sequentially due to instability. This split of the transmission system resulted in the St. Lucie Plant of the east area being tied only to the north area and the Riviera Plant being islanded along with part of the east area load. The south area and the balance of the east area thus became an isolated area with Port Everglades and Turkey Point Plants generating 1003 MW to supply approximately 2950 MW of load. (See Figures 1 and 2.)

This load-generation imbalance resulted in a very rapid drop in frequency to below 56 Hz. Underfrequency relays operated to shed approximately 50/

of the load. The four units operating at Port Everglades and Turkey Point Plants became swamped and tripped off. The Riviera Plant was shut down about 10:30 a.m. due to operational problems following load rejection.

The outage then extended from Ft. Pierce to the Florida Keys and affected approximately 1,300,000 customers. Service was restored to almost all customers by 3:00 p.m.

The east and south areas had been importing approximately 1140 MW just prior to the system split due to the earlier forced outage of Turkey Point Unit 3 at 10:08 a.m. This generation loss of 684 MW had isolated Peninsular Florida but the combined spinning reserve of the Florida systems had been sufficient to cover the loss and arrest the frequency decline at 59.59 Hz.

At 10:14 a.m., Peninsular Florida had been tied back to the systems to the north and operating conditions stabilized. See Figures 3 and 4 for details of inter-area flows, tie flows, loads, generation and spinning reserve.

DESCRIPTION OF DISTURBANCE LOSS OF TURKEY POINT UNIT 3 At 10:08 a.m., May 16, 1977, Turkey Point Unit 3 experienced a reactor and turbine trip as a result of a false relay operation. Chattering contacts in a sensing relay in a reactor coolant pump breaker monitor circuit gave false indication of the loss of a reactor coolant pump. A reactor trip was then initiated since Turkey Point generation was 684 MW. The north-south lines in the state of Florida relayed, isolating the peninsula from the north. The frequency dropped to 59.59 Hz as a result of governor response.

At 10:14 a.m., the tie to the north was re-established and the frequency returned to 60 Hz. There was a heavy import of power south, but was reducing in magnitude. Voltage at St. Lucie Plant 240kV bus was 219kV.

LOSS OF THE FT. MYERS - RANCH 240KV LINE At 10:24 a.m., the Ft. Myers - Ranch 240kV line relayed due to phase-to-ground fault near Ft. Myers. Just prior to this relay action the line was carrying approximately 420 MW. The loss of the Ft. Myers - Ranch 240kV line resulted in a further increase in flow south of Malabar. This power swing caused the separation of the system at 10:24 a.m. (See Figure 1.)

The sequence of relay and breaker operations is given in Figure 5.

Approximately four seconds later, St. Lucie Unit 1 reactor was tripped manually following a run back of the unit. Riviera Units 3 and 4 were isolated into an area with 105 MW of load. The Riviera units were carrying approximately 532 MW prior to the separation of the system. After approx-imately six minutes, the generator breakers at Riviera were opened in order I

to stabilize the units.

The frequency in the remaining affected area decreased rapidly due to Turkey Point Units 1 and 2 and Port Everglades Units 1 and 3 with 1003 MW of generation being left to serve approximately 2957 MW of load (See Figure 2.) Within two seconds, frequency dropped below 56 Hz. As the frequency dropped, underfrequency relays shed approximately 1544 gay MW

~Z~4 in s'tages beginning at 59.2 Hz and completing the shed at 57.1 Hz. Turkey Point Unit 2 and Port Everglades Unit 3 tripped with low bearing oil pressure signal. Port Everglades Unit 1 and Turkey Point Unit 1 were tripped by operation of generator underfrequency protection set at 57.0 Hz with a 12-second delay.

See Figure 6 for a sequence of events for the affected plants during the disturbance.

The remainder of the system, north and west of the split, went into high frequency but recovered to 60 Hz and the north-south ties were

re-established. The remaining system load was H58 MW and 1798 MW of g lfO.

0C generation. Net export was 240 MW nti 'chedu/ed interchange was re-established.

INITIAL SERVICE RESTORATION The Power Coordinators proceeded to identify the affected area and reconnect the system. Restoration proceeded from the north by energizing the 240kV transmission lines to the south. At 12:03 p.m., the total system load was 3408 MW with 3318 MW of generation and 90 MW of import from neighboring utilities.

LOSS OF THE ANDYTOWN - ORANGE RIVER 500KV LINE At 32:03 p.m., the fault pressure relay on the "A" phase 240/500kV autotransformers at Andytown operated incorrectly when the auxiliary cooling pumps were started. Approximately 652 MW were being carried on the 500kV circuit when tripped was initiated. See Figure 7 for load, generation, and inter-area flow data.

This initiated a power swing which resulted in the separation of the east and south areas at Malabar. See Figure 8 for the area affected.

All generation in the affected area was separated by underfrequency generator protection and overcurrent relay operation.

SERVICE RESTORATION The affected area was quickly identified and immediate restoration

,.....~proceeded from the north. Gas turbines quickly picked up isolated areas and were re-synchronized with the system. Startup power was provided to II the steam units rapidly from the restored 240kV system.

Service was restored to all but a few isolated areas by 3:00 p.m.

There was no damage to generating equipment or to nuclear reactors. All units were returned to service during the day after safety inspections were complete.

SYSTEH CONDITIONS P rior to the disturbance, the system 1oad was 4660 WW with generation of 4710 HH. The system spinning reserve was 400 HM with an additional 1022 HM of available steam reserve and 1571 HW of fast start combustion turbines and diesels. All line flows were well within limits. Area loads and generation data is given in Figure 3 for the loss of Turkey Point Unit 3 i disturbance, Figure 2 for the loss of the Ft. Hyers - Ranch 240kV line, 'and Figure 7 for the loss of the Andytown - Orange River 500kV line.

Figure 4 gives the unit loading and reserves at 10:08 a.m. prior to any disturbances. Figure 5 lists the relay actions occurring during the disturbances.

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figure 2 EvENT loss of ft. M ers - Ranch 240kV Line TIME ]

Net Interchange Before After NORTH BEFORE AFTER 527 in 240 out LOAD 722 705 367 B GEN. 899 806 80 A Outside Ties 320 A 160 B 181 A 544 B WEST EAST B:.F'R- AFTER BEFORE AFTER

/'OAD 672 LOAD 792* 286 595 B GEN. 1175 992 GEe> ~ 1286 105 0 A 0 A 1633 B SOUTH B:-.. ORE AF:.R Out 2636 0 GEN. 1003 SYSTEM BEFORE A" TER I

LOAD 4890 1663 A=After B=Before GEN. 4363 1903 *321 A~IW isolated with South area after system split.

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Net Znte change NORTH After BEFORE AFTER Before

~15 B 50 out 501 in LOAD

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Outside Ties 35' 475 A 62 B 1604 A iZST EAST BE.".ORE AFT F. 'BE. ORE A". T:-R r

LOAD 705 710 LOAD 715 755 290 Bm 1255 1308 GEN. 1030 1112 562 A-p 1590 A 892 B SOUTH oe- A:T:.R Open LOAD 2560 2590 GBN. 1668 1000 SY STRE BBE OR:-

LOAD 4660 4735 G:-N. 4710 4234 A=A te B=Before

I Figure 4 RLT:3f FLORIDA POWER & LIGHT COMPANY NET UNIT CAPABILITY-MWAT 10:08 AM MAY 16, 1977 PLANT CONTINUOUS ACTUAL UNIT RATE M+P ~ LOAD SR NORMAL LIMITATION TPNl 369 369 328 41 TP02 369 185 188 0 5 PM Seal leak "A" BFP.

TPN3 681 681 684 0 TPN4 681 0 0 7-17-77 Refuel.

FL54 138 0 0 RFC 12:30P FLS5 138 0 0 RFC 2:OOP PE51 205 90 90 0 Condenser leak.

PEN2 205 0 38 0 RFC ll:OOA Not released.

PEN3 368 368 340 28 PEÃ4 368 0 0 5-28-77 Overhaul.

3522 1693 1668 69 RVS3 273 273

~vN4 273 273 501 45 111 809 751 754 Unknown Heater drain pump out.

1355 1297 1255 CCSl 369 369 333 36 CC11 2 364 173 166 7 5-18-77 2B FD fan motor repair.

SNN3 138 0 0 RFC 2:OOP SNÃ4 370 370 258 61 SN115 370 0 0 RFC 1: OOP 1611 912 757 104 138 138 106 23 FM52 369 369 339 30 MT51 772 772 585 129 1279 1279 1030 182 STEJQ1 7767 5181 4710 400 DSL 27 24 0 0 PE 02 will not start.

GTPE 338 310 0 0 5-16>>77 512 maint.

GTF L 676 676 0 0 519 base only.

GTFM 612 561 0 0 5-20-77 I7 gen. ground.

1653 1571 TOTAL 9420 6752 4710 400 Scheduled interchange = 0 Required Spinning Reserve = 337 Expected Mon. a.m. peak = 5000 Sun. p.m. peak was 4442 MW.

Weather: Mostly suey today and Tuesday. Hi in lo 80's. Lo in lo 70's.

Wind East 10 MPH.

SYSTEM Dl STURBANCE SUMHARY OF RELAY AND BREAKER OPERATIONS TIME STAT I ON CIRCUITS fVL'NTS REHARKS

]0:08AM Turkey Point Unit //3 Tripped 10:09:50RH Port Evergia<les Uni t //2 Tripped 0 Ranch Fort Hyers-Ranch 240kV Opened GP (10: 24AM)

Fort Hyers Fort Hyers-Ranch 240kV Opened PP, Zl., G I Unl'nown For t Hyers Fort Myers Ranch l38I<V Opened A,B>C, PP 53 Cy Halabar Mal abar-Hi dway 240kV No. 1 Opened A,B, PP,Z) 55 Cy Midway Midway-Ranch 240kV Opened ApB,PP,Zl 60 Cy(approx) Ranch Pratt 6 Whitney-Ranch Opened A~Zl 240kV 60 Cy(approx) Pratt f. Whitney Pratt G Whitney-Ranch Opened BpCpZ'3 240kV y8 CV(aVV~ox) Broward Broward-Ranch l38kV Opened A,C,PP 78 Cy(approx) Ranch Broward-Ranch 3.38kV Opened A,C, PP Unknown llartman liartman-Midway 69kV Opened Unknown llartman llartman-Midway 69I<V Reclosed

T I I'lE STATION CIRCUITS EVENTS REHARKS O'I Cy(approx) Riviera Ranch-Riviera 138I V No. 2 Opened B,Cp Z2 85 Cy(approx) Riviera Ranch-Riviera 130I<V No. 3 Opened B,C,Z2 00 Cy(approx) Il i dway Hidway-Plumosus 130I<V Opened A,B,C,PP 00 Cy(approx) P lumosus Hi dway-Pluinosus 138I<V Opened

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.1.00 Cy(approx) Ranch Ranch-West Palm Beach Opened C,PP,Zl 138I<V 127 Cy(approx) Ranch Ranch-West Palm Beach Reclosed 138I<V l>I3 Cy(approx) Ranch Ranch-West Pahn Beach Opened C, PP,Z1 130I<V 280 Cy(approx) St. Lucie Unit /ll Tripped

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'vENT Loss of And town - Oran e River 500kV TIVE 12: 03 .m.

Net Interchange Before After NORTH 90 in 516 out BEFORE A. TER 30 B LOAD 740 721 GEN. 1004 727 6 A 0 A 294 B 510 A 60B tI:S EAST OF:.

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