March 30, 2011 Draft

F. Local Reliability Rule

The local reliability rule for Northport Gas Burn (IR-5) for 2011 remains the same as last 

year and are provided as a guide for unit commitment. Use of information from the 2010

Summer Operating Study are still valid since there have been no significant system 

changes in the area. For the 2010 period an analysis was conducted to determine the Long 

Island load level up to which Northport units can be permitted to burn gas depending on 

how many units are online as well as the number of cables in service. Power flow 

simulations were prepared to represent the instantaneous loss of fuel, with those units 

continuing to produce MVAR output for 20 minutes. During this time, operators would 

be able to put quick start GTs online, increase remaining steam units to their DMNC 

capabilities, adjust phase shifters, and switch on capacitor banks as needed.

TABLE II-F-1

Steam Generation Resources at Northport

Unit Ratings (MW)

DMNC Continuous

Northport Steam 1 395.0 363

Northport Steam 2 381.7 363

Northport Steam 3 395.2 363

Northport Steam 4 399.2 363

Total 1571.1 1452

1. Assumptions

Several base assumptions, depending on the case, were made to observe conservatism 

and to make a stressed case. These assumptions are as follows:

· 91% System Power Factor (note: it does vary by bus location)

· Northport Units online at DMNC 

· One Barrett Steam Unit online

· Caithness CC online

· Dunwoodie and Sprainbook series reactors in service (Y49 series reactor 

bypassed)

· Four (4) shunt reactors in service on Y49 and Two (2) shunt reactors in service on 

Y50

· Northport Norwalk Harbor (NNC)

i. In service

1. Importing 100 MW with only 2 Cable in Service

2. Importing 200 MW with 3 Cables in service1

· Neptune import of 660 MW with 0 MVAR flow

· Contractual MVAR flow split on Y49, Y50 & NNC

· Capacitor banks and generation were adjusted based on load level

 

1 LIPA received permission to increase the flow from 100 MW to 200 MW effective April 1, 2010 on the condition 

that all 3 cables are in-service. With only 2 cables the limit remains at 100 MW. Note, importing 200 MW with all 4 

units at DMNC would result in overloads above LTE on the Northport exits – See Northport exit section of the 

report. 
March 30, 2011 Draft

2. Analysis

Attached Tables and Diagrams:

· Diagrams II-F-2 (a-c) show the results of this analysis for two, three, and four 

Northport units, 

· Tables II-F-2 (a-c) list the generation dispatch assumed to obtain operating limits

· Table II-F-2d is the listing of the reactive resource dispatch assumed2

· Table II-F-2e is the guideline for how many units must be run on oil at various 

load levels depending on how many Northport units are online

All charts included in the following section, assume 2 NNC cables in-service with 

100 MW of imports. Additional tests were performed with 3 NNC cables in-service 

and 200 MW of imports but are omitted here as the results are very similar.

Additional Comments:

· At each load level, the loss of gas supply was simulated by reducing the MW 

output of the Northport steam units to zero and fixing their MVAR output to prefault levels.

· The point at which the voltage on the 138 kV system crossed 0.95 p.u. on 

contingency (violates criteria) was used as the operating limit. Using a 5% safety 

margin from that point is the recommended Long Island system load level for 

running Northport units on gas.

· With the new NNC cables and LTE/STE ratings in place, the LTE overloads on 

the NNC for loss of three Northport units have been reduced from prior years. 

With 2 cables in-service there is a small LTE overload and completed eliminated 

with 3 cables in-service.3,4 Adjusting inter-ties and on-island generation can be 

used to rebalance loadings if needed.

· For the loss of Northport units, turning on quick start GTs at Barrett and 

Holtsville and/or reducing the Con Edison wheel helps compensate for the MW 

loss. After the quick start GTs are online, system voltages are within criteria. 

Load flow simulations confirm that after the MVARs from the Northport units are 

lost, system voltages recover to acceptable levels.

· Installation of Caithness in 2009 provided additional voltage support on 

contingency since the unit has more MVAR capability than other on-island 

generators and with its higher efficiency, it is expected to be in operation. This 

allowed for Northport units to burn gas at slightly higher load levels.

 

2 This dispatch did not apply for the higher load levels at which point the pre-contingency voltage was outside 

criteria so the capacitors were allowed to adjust for voltage.

3 MW Flows on the Y49 and Y50 interties were split for this study. If Y49 carries more than about 630 MW, it will 

reach LTE for the loss of 3 Northport units.

4 With 3 cables in service there would be no LTE overload on NNC occurs for loss of three Northport units due to 

the use of the new LTE ratings of 540 MVA (the old LTE limit for the 1385 cable system was 335 MVA). 

However, with 2 cables in service there would be an approximate 10% overload based on the 2 cable LTE rating of 

384 MVA. Separately, the administrative limit on the normal rating for NNC of 286 MW with 3 cables in-service 

will no longer be binding for 2011 due to approval of an SIS in December of 2010. Actual normal ratings will be 

based on actual equipment limitations.
March 30, 2011 Draft

DIAGRAM II-F-2A

Transmission Voltages for the Loss of Gas Supply at Northport

L/O 2 Northport Units with 2 Units Online

2 Cables In-Service 100 MW on NNC

TABLE II-F-2A

Generation Dispatch for Diagram II-F-2A 

Transmission Voltage

L/O 2 Northport Units (2 Online) with

Pre-contingency MVAR Limit

0.90

0.91

0.92

0.93

0.94

0.95

0.96

0.97

0.98

0.99

1.00

1.01

1.02

1.03

1.04

2925 2975 3025 3075 3125 3175

System Load (MW)

Voltage (p.u.)

5pct RVRHD 138 CANAL 138

RONKONK 138 C.ISLIP 138 PT JEFF1 138

Series4 Series8 Series9

5% Safety Margin

3100 * 95% =2945 MW

Inter-ties 3000 3050 3100 3150 3200 3250

Purchases via Y49 469 494 519 544 571 594

Purchases via Y50 470 494 521 545 571 594

Con Ed Wheel -286.4 -286.9 -286.9 -287.4 -286.9 -287

Purchases via NNC 101 100 100 101 100 101.8

Purchases via CSC 330 330 330 330 330 330

Purchases via Neptune 661 661 661 661 661 661

MVAR Flow on Neptune -5.8 -4.6 -8.2 -7.2 -5.6 -8.4

Generation

Barrett 1 191.2 192.8 192.9 184.1 184.4 193.4

Northport 2 381.7 381.7 381.7 381.7 381.7 381.7

Northport 3 395.2 395.2 395.2 395.2 395.2 395.2

Caithness CC 286.0 286.0 286.0 286.0 286.0 286.0

2 Northports Online Load Level (MW)
March 30, 2011 Draft

DIAGRAM II-F-2B

Transmission Voltages for the Loss of Gas Supply at Northport

L/O 3 Northport Units with 3 Units Online

2 Cables In-Service 100 MW on NNC

TABLE II-F-2B

Generation Dispatch for Diagram II-F-2B

Transmission Voltage

L/O 3 Northport Units (3 Online) with

Pre-contingency MVAR Limit

0.90

0.91

0.92

0.93

0.94

0.95

0.96

0.97

0.98

0.99

1.00

1.01

1.02

1.03

1.04

2925 2975 3025 3075 3125 3175

System Load (MW)

Voltage (p.u.)

5pct C.ISLIP 138 RONKONK 138

RVRHD 138 CANAL 138 PT JEFF1 138

5% Safety Margin

3100 * 95% =2945 MW

Inter-ties 2950 3000 3050 3100 3150 3200 3250

Purchases via Y49 248 272 298 322 349 372 399

Purchases via Y50 247.4 273.5 298 323 346 373.5 396

Con Ed Wheel -286.9 -287.2 -286.8 -287.2 -287.5 -287 -286.9

Purchases via NNC 100.2 100.4 99.5 101 101 100.5 100.1

Purchases via CSC 330 330 330 330 330 330 330

Purchases via Neptune 661 661 661 661 661 661 661

MVAR Flow on Neptune -4.2 -3.2 -7 -5.6 -5.8 -9 -7.2

Generation

Barrett 1 187.7 188.6 189.7 190.7 186.7 187.8 189.6

Northport 1 395.0 395.0 395.0 395.0 395.0 395.0 395.0

Northport 2 381.7 381.7 381.7 381.7 381.7 381.7 381.7

Northport 3 395.2 395.2 395.2 395.2 395.2 395.2 395.2

Caithness CC 286.0 286.0 286.0 286.0 286.0 286.0 286.0

3 Northports Online Load Level (MW)
March 30, 2011 Draft

DIAGRAM II-F-2C

Transmission Voltages for the Loss of Gas Supply at Northport

L/O 3 Northport Units with 4 Units Online

2 Cables In-Service 100 MW on NNC

TABLE II-F-2C

Generation Dispatch for Diagram II-F-2C 

Transmission Voltage

L/O 3 Northport Units (4 Online) with

Pre-contingency MVAR Limit

0.90

0.91

0.92

0.93

0.94

0.95

0.96

0.97

0.98

0.99

1.00

1.01

1.02

1.03

1.04

3250 3300 3350 3400 3450 3500

System Load (MW)

Voltage (p.u.)

Knee Of Curve 5pct C.ISLIP 138

RONKONK 138 RVRHD 138 CANAL 138

PT JEFF2 138

z

3440 * 95% =3268 MW

5% Safety Margin

Inter-ties 3250 3300 3350 3400 3450 3500

Purchases via Y49 198 222 246.5 273 298 322

Purchases via Y50 198.5 224.3 248 272.4 297.6 322

Con Ed W heel -287.1 -287.3 -286.9 -286.9 -286.7 -287.2

Purchases via NNC 101.3 101.3 101.3 100.2 100.2 101

Purchases via CSC 330 330 330 330 330 330

Purchases via Neptune 661 661 661 661 661 661

MVAR Flow on Neptune -6.2 -10.2 -9.2 -8.4 -8 -6.8

Generation

Barrett 1 187.6 188.6 190.8 192.0 192.9 190.6

Northport 1 395.0 395.0 395.0 395.0 395.0 395.0

Northport 2 381.7 381.7 381.7 381.7 381.7 381.7

Northport 3 395.2 395.2 395.2 395.2 395.2 395.2

Northport 4 399.2 399.2 399.2 399.2 399.2 399.2

Caithness CC 286.0 286.0 286.0 286.0 286.0 286.0

4 Northports Online Load Level (MW)
March 30, 2011 Draft

TABLE II-F-2D

MVAR Reactive Resource Dispatch for Loss of Northport Units

2Cables In-Service 100 MW on NNC5

Bus Name Max Dispatch 

BARRETT1 138.00 -75 0

NRTHPT2 138.00 -75 0

PILGRIM 138.00 104 0

HOLBROOK 138.00 104 0

HOLTS GT 138.00 104 0

RVRHD 138.00 -27 0

FARRCK1 69.000 54 54

VLYSTRM2 69.000 54 54

E.G.C.2 69.000 54 0

GLNWD SO 69.000 54 54

MASPEQUA 69.000 54 54

NEWBRGE1 69.000 54 54

NEWBRGE2 69.000 54 0

FLWRFLD 69.000 27 27

INDIANHD 69.000 27 0

PILGRM 69.000 108 108

RULND RD 69.000 108 54

WOLFHILL 69.000 27 0

BRGHTWTR 69.000 54 0

BRNTWOOD 69.000 54 0

STERLING 69.000 54 0

WATSON 69.000 54 54

HOLBRK1 69.000 54 54

HOLBRK2 69.000 54 0

JAMESPRT 69.000 14 0

MORICHES 69.000 28.8 28.8

PECONIC 69.000 14 14

PTCHOGUE 69.000 27 0

RIDGE 69.000 28.8 0

SOUTHOLD 69.000 -23.31 0

WILDWOOD 69.000 28.8 0

BRGHMPTN 69.000 14 0

BUELL 69.000 14 0

EHAMP 69.000 14 0

RIV 1 69.000 27 27

RIV2 69.000 27 0

SOHMPTN 69.000 22.55 14

TEMPLE 69.000 24.5 24.5

TIANA 69.000 27 27

GRN ACRE 34.500 12 12

MONTAUK 23.000 7.2 0

TOTAL 1641.65 714.3

%On 43%

%Off 57%

 

5 The above table reflects capacitor banks on line for all loads except for high load level cases, e.g., above 5,000 

MW, in which all banks were dispatched.
March 30, 2011 Draft

TABLE II-F-2E

6

Guideline for Running Northport Units on Oil

NNC In-Service

2 Cables In-Service 100 MW Import or

3 Cables In-Service 200 MW Import 

Load Level Northport Units Online

One Two Three Four

0-2950 0 0 0 1

2951-3250 0 1 1 1

3251-5450 0 1 1 2

5451-6000 0 1 2 3

Note1: Differences between 2 and 3 cable operation are not significant

Note2: Northport Gas Burn Rule Guideline for NNC In Service in 2011 was 

provided as a guide and are based on the 2010 Summer Operating study since 

there have been no significant system changes.

6 

- Values in table II-F-2E above indicate the number of units that can be run 

on oil. For example, with NNC In-Service, if three Northport units are online, 

none have to be run on oil (all three can be on gas) up to a load level of 2950

MW. Starting at 2951 MW, only one of the three units must be on oil (2 on 

gas) up to a load level of 5450 MW after which 2 units must be on oil.