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 Introduction Surrmary Description of Disturbance Loss of Turkey Point Unit 3 Loss of the Ft. Myers - Ranch 240kV Line Initial Service Restoration PAGE 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 Figure 6 - Sequence of Events Figure 7 - Area Loads and Generation Figure 8 - Hap of Area Affected - Loss of Orange River 500kV Line 10 12 13

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 gay ~Z~4

dropped, underfrequency relays shed approximately 1544 MW 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 Prior 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.

Figure 1

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Net Interchange Before After 527 in 240 out NORTH BEFORE AFTER Outside Ties 367 B

80 A LOAD GEN.

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• 321 A~IW isolated with South area after system split.

Figure 3

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Net Znte change Before After 50 out 501 in

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NORTH BEFORE AFTER Outside Ties 35' 1604 A 475 A 62 B

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Figure 4

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& LIGHT COMPANY NET UNIT CAPABILITY-MWAT 10:08 AM MAY 16, 1977 PLANT UNIT CONTINUOUS RATE M+P ~

ACTUAL LOAD SR NORMAL LIMITATION TPNl TP02 TPN3 TPN4 FL54 FLS5 PE51 PEN2 PEN3 PEÃ4 369 369 681 681 138 138 205 205 368 368 369 185 681 0

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Overhaul.

3522 1693 1668 69 RVS3

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

1355 1297 1255 CCSl CC11 2 SNN3 SNÃ4 SN115 369 364 138 370 370 369 173 0

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61 5-18-77 RFC 2:OOP RFC 1: OOP 2B FD fan motor repair.

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1653 1571 TOTAL 9420 6752 4710 400 Scheduled interchange

= 0 Expected Mon. a.m.

peak

= 5000 Weather:

Mostly suey today and Wind East 10 MPH.

Required Spinning Reserve

= 337 Sun.

p.m. peak was 4442 MW.

Tuesday.

Hi in lo 80's.

Lo in lo 70's.

SYSTEM Dl STURBANCE SUMHARY OF RELAY AND BREAKER OPERATIONS TIME

]0:08AM 10:09:50RH 0

(10: 24AM)

STAT I ON Turkey Point Port Evergia<les Ranch Unit //3 Uni t //2 CIRCUITS Fort Hyers-Ranch 240kV fVL'NTS Tripped Tripped Opened GP REHARKS Unl'nown 53 Cy 55 Cy 60 Cy(approx)

Fort Hyers For t Hyers Halabar Midway Ranch Fort Hyers-Ranch 240kV Fort Myers Ranch l38I<V Opened Opened Midway-Ranch 240kV Pratt 6 Whitney-Ranch 240kV Opened Opened Mal abar-Hi dway 240kV No. 1 Opened PP, Zl., G I A,B>C, PP A,B, PP,Z)

ApB,PP,Zl A~Zl 60 Cy(approx)

Pratt f. Whitney Pratt G Whitney-Ranch 240kV Opened BpCpZ'3 y8 CV(aVV~ox) 78 Cy(approx)

Unknown Unknown Broward Ranch llartman llartman Broward-Ranch l38kV Broward-Ranch 3.38kV liartman-Midway 69kV llartman-Midway 69I<V Opened Opened Opened Reclosed A,C,PP A,C, PP

T I I'lE STATION CIRCUITS EVENTS REHARKS O'I Cy(approx) 85 Cy(approx) 00 Cy(approx) 00 Cy(approx)

<)0 Cy(approx)

.1.00 Cy(approx)

Riviera Riviera Ili dway P lumosus Ranch Ranch Hidway-Plumosus 130I<V Hi dway-Pluinosus 138I<V Ranch-Riviera 138kV No.l Ranch-West Palm Beach 138I<V Opened Opened Opened Opened Ranch-Riviera 138I V No.

2 Opened Ranch-Riviera 130I<V No.

3 Opened B,Cp Z2 B,C,Z2 A,B,C,PP A,BpC,Z3 C,PP,Zl 127 Cy(approx)

Ranch l>I3 Cy(approx)

Ranch 280 Cy(approx)

St. Lucie Ranch-West Palm Beach 138I<V Ranch-West Pahn Beach 130I<V Unit /ll Reclosed Opened Tripped C, PP,Z1

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Net Interchange Before After 90 in 516 out NORTH BEFORE A. TER 30 B

LOAD 740 721 6 A GEN.

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