Short Circuit Studies

Feasibility Study
Shaw Environmental, Inc.
12MW Landfill Gas Generation Interconnection
J.E.D. Solid Waste Management Facility
Holopaw Substation
September 2013
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Table of Contents
GENERAL ..................................................................................................................................... 3
SHORT CIRCUIT STUDIES ...................................................................................................... 4
CASES STUDIED ............................................................................................................................ 4
AVAILABLE FAULT CURRENTS ..................................................................................................... 4
IMPACT OF SHAW ENVIRONMENTAL GENERATION ON FEEDER .................................................... 4
LOAD FLOW STUDIES .............................................................................................................. 5
CASES STUDIED ............................................................................................................................ 5
VOLTAGE CONDITIONS ................................................................................................................. 5
POWER FLOW CONDITIONS ........................................................................................................... 5
IMPACT OF SHAW ENVIRONMENTALADDITIONAL GENERATION ON FEEDER ................................ 5
SYSTEM PROTECTION AND GROUNDING REVIEW
UNINTENTIONAL ISLANDING ......................................................................................................... 6
FEEDER PROTECTION .................................................................................................................... 6
GROUNDING ................................................................................................................................. 6
STABILITY ANALYSIS ............................................................................................................. 7
RECOMMENDED CONFIGURATION.................................................................................... 8
INTERCONNECTION ...................................................................................................................... 8
Primary facilities ..................................................................................................................... 8
System protection: Unintentional islanding ............................................................................ 8
System protection: other functions required ........................................................................... 8
VOLTAGE REGULATION ................................................................................................................ 9
Shaw Environmental Generation ............................................................................................ 9
M0629 feeder .......................................................................................................................... 9
HOLOPAW SUBSTATION UPGRADES ............................................................................................ 10
Feeder protection .................................................................................................................. 10
INTERCONNECTION FACILITIES ...................................................................................... 11
PRIMARY FACILITIES .................................................................................................................. 11
PROTECTION & CONTROL FACILITIES ......................................................................................... 11
INTERCONNECTION FACILITIES ESTIMATES .............................................................. 12
PRIMARY FACILITIES ................................................................................................................. 12
SUBSTATION, PROTECTION AND CONTROL ................................................................................. 12
FEEDER W0629 ........................................................................................................................... 12
COST SUMMARY ......................................................................................................................... 12
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General
Shaw Environmental has submitted to Duke Energy Florida (DEF) a Generator
Interconnection Service Request for its Landfill Gas to Energy Project. Shaw
Environmental intends to interconnect 12 MW of generation with the Duke Energy
Florida (DEF) distribution system. Connection will be to feeder W0629 out of DEF’s
Holopaw substation and near the JED Landfill located in Osceola County, Florida.
Interconnection of the Shaw Environmental proposed 12 MW generation to the DEF
W0629 feeder at the JED Landfill is feasible, provided the generation is operated within
certain parameters, specific Interconnection Facilities are installed and certain necessary
System Upgrades are completed.
This document contains applicable study results, based on initial studies of the proposed
interconnection configuration and equipment specifications per the July 22, 2013 scoping
meeting. The estimated cost of the Interconnection Facilities and any necessary System
Upgrades to allow interconnected operation of the facility are also included but may not
be all inclusive. Determination of a definitive in-service date as well as the associated
cost of upgrades and equipment will require further study.
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Short Circuit Studies
Cases studied
Short circuit studies were run in which the DEF system and Shaw Environmental’s
generation were considered as sources able to contribute fault current for faults on the
Holopaw Substation W0629 feeder. All faults are modeled as bolted faults with zero
fault impedance. Shaw Environmental’s generation fault contributions were modeled
using transient reactances. The results of the studies are at the end of this section.
Available fault currents
In the planned configuration (delta/wye-grounded step-up transformer), Shaw
Environmental’s generation facility will increase fault currents on the feeder at certain
locations. At the Holopaw substation bus the available three phase fault current will
increase by 45% and the phase to ground fault current will increase by 38%. At the point
of interconnection the available three phase fault current will increase by 110% and the
available phase to ground fault current will increase by 156%.
Impact of Shaw Environmental generation on feeder
Interrupting ratings of protective devices are affected by the addition of the 12 MW
generation. Approximately six (6) existing recloser installations will have their fault
current rating exceeded with the addition of this generation and will need to be upgraded
to reclosers with a higher fault duty rating.
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Load Flow Studies
Cases studied
Load flow studies were performed for multiple cases of Holopaw Feeder W0629 in order
to determine system conditions with and without the 12 MW Shaw Environmental’s
generation under various circumstances.
Voltage conditions
Studies indicated that acceptable voltage levels (between 95% and 105% of nominal) and
load flows would be maintained with the Shaw Environmental’s generators operating at
unity (1.00) power factor, provided that the required system upgrades are completed. The
only exception is at the generator’s metering point where voltage was calculated at
105.2% of nominal.
Power flow conditions
For purposes of this analysis a minimum load on the W0629 Feeder of 41, 47 and 48
amps (~ 2 MW), on A, B, and C phase respectively, was used. A maximum load on the
W0629 Feeder of 173, 202 and 197 amps (~8.2 MW), on A, B, and C phase respectively
was used. Both of these cases are without any contribution from the Shaw Environmental
generator.
Feeder W0629 is the only feeder connected to the Holopaw substation bank #2
transformer, which consists of 3 single phase 3.33/4.166/4.666 MVA, 230 kV to 25 kV
transformers.
Impact of Shaw Environmental generation on feeder
It is important to note that the Shaw Environmental generation (12 MW) at the JED
landfill shall cause reverse power flow situation at the substation for all periods of
operation. This was expected and planned for and shall not cause any operational
problems provided the generation maintains a 1.00 Power Factor at all times.
The maximum calculated reverse power flow on feeder W0629 (at Bank #2 in the
substation) was an export (to transmission) of 9.7 MW with an import (from
transmission) of 1.4 MVAR. The minimum calculated reverse power flow on feeder
W0629 (at Bank #2 in the substation) was an export (to transmission) of 3.2 MW with an
import (from transmission) of 3.1 MVAR.
Recloser 6156648 (located on 441 just south of 17/92) is located between the substation
and the generator and thus will experience reverse current flow when the generators are
operating. The maximum reverse current will be about 235 amps. This will need to be
studied in more detail to ensure appropriate operation of this device during abnormal
situations.
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System Protection and Grounding Review
Unintentional islanding
Due to the capacity of the generation as compared with the feeder load, unintentional
islanding is of significant concern. A transfer trip protection scheme from Holopaw
substation to the Shaw Environmental generation site (at JED Landfill) shall be required.
Feeder protection
The existing regulator control is being evaluated by Duke Protection and Control
Department.
The Recloser 6156648 (located on 441 just south of 17/92) is currently a Cooper VWE
and will need to be upgraded to a G&W Viper.
A new recloser (G&W Viper) will need to be installed at the start of the new tap line for
the generators at the Landfill entrance and 441.
Approximately six (6) existing recloser installations (type E) will have their fault current
rating exceeded with the addition of this generation and will need to be upgraded to
reclosers with a higher fault duty rating (type 4E).
Grounding
Grounding specifications supplied by Shaw Environmental for the generators and step-up
transformer have been reviewed with no DEF objections. All Shaw Environmental’sowned equipment will be expected to comply with all applicable codes regarding
grounding.
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Stability Analysis
Due to the size and nature of this feeder and generating facility, stability analysis was not
performed. The use of transfer trip with other appropriate backup relay functions should
assure quick separation of Shaw Environmental’s generation from the DEF system.
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Recommended configuration
The recommended configuration required for the Holopaw W0629 feeder in order to
allow operation of Shaw Environmental generation is as follows.
Interconnection
Primary facilities
The Shaw Environmental generation can be connected at the proposed location, with the
following modifications:
1. New 795 AAC three phase overhead line from generator interconnection (primary
meter) point to Landfill entrance on SR 441 (approximately 3 miles)
2. Reconductor existing 336 AAC overhead three phase line from Landfill entrance
on SR 441 North to intersection of SR 441 with US 17/92 (approximately 9 miles)
3. Installation of new recloser (G&W Viper) on new line to generator at Landfill
entrance and SR 441.
4. Installation of Primary Metering at generator location.
System protection: Unintentional islanding
1) Isolate Plant during loss of Transmission Voltage or Distribution Bus voltage at
Holopaw Substation. A Direct Transfer Trip will be send to isolate the plant in
order to avoid unintentional islanding.
2) Actual Step Up Transformer at Plant is 10/12/14 MVA, Duke Energy Distribution
Transformers are 3 single phase units with total of 10 MVA. The excess
generation towards Transmission System shouldn’t exceed 10 MVA.
3) Loss of feeder W-629 will result in loss of auxiliary power (Station Service) for
the plant.
4) Additional sources of auxiliary power at the plant shouldn’t back feed into feeder
W-629 to provide an ungrounded system source.
System protection: other functions required
Although transfer trip should clear Shaw Environmental generation off line for most
abnormal feeder conditions, any protection scheme utilizing remote communications as a
primary protection scheme requires backup protection functions. The interconnection
relaying referenced earlier will be used, at a minimum, for the following functions:
 27
 59
 81O/U
 51V
 46
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Voltage regulation
Shaw Environmental generation
DEF will require Shaw Environmental Generation to not actively regulate the voltage at
the interconnection point. Rather, Shaw Environmental generation shall operate at unity
(1.00) power factor. Shaw Environmental generation could potentially run at the
maximum KW allowed by the generators’ capability curve while maintaining the
prescribed power factor.
DEF will specify the power factor at which to operate in order to minimize the effects of
the generation on the voltage levels for DEF retail customers on the W0629 feeder. DEF
may require Shaw Environmental generation to change its power factor from time to time
as changes in the DEF system warrant.
W0629 feeder
Since there will be reverse power flow through the Holopaw substation transformer,
existing 25 KV voltage regulation at the substation may require equipment modifications
to handle this reverse power flow. Further review via the more detailed System Impact
Study will be needed.
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Holopaw substation upgrades
1) Since Holopaw Distribution Bank # 2 (230/25KV) is tapped off the West Lake
Wales 230KV circuit, a 230KV Breaker will be installed in place of circuit
switcher 1122. Protection and Control devices (for this breaker) will be required
to help determine generation input.
2) Install potential transformers at feeder location to monitor load side of the feeder
breaker W-629.
3) Install SEL-351S6 Control relay at the Feeder W-629.
4) Fiber Optic communication media between JED plant and Holopaw Substation
must be installed to interface devices between Feeder protection and JED plant
protection relays. This allows control and data exchange between Duke and JED.
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Interconnection Facilities Estimates
Primary facilities
 New 795 AAC three phase overhead line from generator interconnection (primary
meter) point to Landfill entrance on SR 441 (approximately 2 miles)
 Reconductor existing 336 AAC overhead three phase line from Landfill entrance
on SR 441 North to intersection of SR 441 with US 17/92 (approximately 9 miles)
 Installation of new recloser (G&W Viper) on new line to generator at Landfill
entrance and SR 441.
 Installation of Primary Metering at generator location.
The cost estimate for these facilities is $1,800,000.
Protection & control facilities
1) Substation- 230 KV Breaker, Slab extension, Grounding Labor, Conduits, Splice
box, Removal of existing Circuit switcher.
2) P&C – Potential transformers, Protection relays, Communication Materials,
Cables, Relay panels, Communication Interface devices, Control wiring, Relay
settings and Commissioning.
3) Fiber Optic Cable (ADSS) and installation for 12 miles.
The cost estimate is $ 900,000
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W0629 feeder
 The Recloser 6156648 (located on 441 just South of 17/92) is currently a Cooper
VWE and will need to be upgraded to a G&W Viper.
 Approximately six (6) existing recloser installations (type E) will have their fault
current rating exceeded with the addition of this generation and will need to be
upgraded to reclosers with a higher fault duty rating (type 4E).
The cost estimate for these facilities is $85,000.
Feasibility Study Cost Estimate Summary
25 kV Feeder reconductor and new line section $1,800,000
construction
Protection , Control , Communications and new 230 kV
$900,000
breaker
New 25 kV Reclosers
$85,000
TOTAL
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$ 2,785,000

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