South Dakota 890 Study
September 16, 2011
South Dakota 890 Study
• Presentation of 890 Study results from
2011
– Includes
I l d WAPA suggested
t d system
t
improvements and timelines
• Stakeholder Feedback
• Questions?
2
Western South Dakota
3
Western South Dakota System
Improvements During 2011
–Increased size of Rapid City Capacitor Banks
•Capacitors were increased from 13.11 MVAR to 17.48 MVAR April 2011
–Installation
I t ll ti off Rapid
R id City
Cit A
Area UVLS
•Three stages of UVLS were installed at the Rapid City Substation in May 2011 to shed load if 115 kV voltage remains below
0.88 pu for 3 seconds
–Installation of Pierre Area UVLS
•Three stages
g of UVLS are installed at the Pierre Substation in May
y 2011 to shed load if 115 kV voltage
g remains below 0.88 p
pu
for 3 seconds
•One stage of UVLS is installed at the Irv Simmons Substation in May 2011 to shed load if 115 kV voltage remains below 0.88
pu for 3 seconds
–Bus Replacement at Midland Substation
•Replaced
p
limiting
g buswork and jjumpers
p
May
y 2011
–Bus Replacement at Wall Substation
•Replaced limiting buswork and jumpers May 2011
–Bus Replacement at Wicksville Substation
•Replaced limiting buswork and jumpers May 2011
–Raised limiting structures on Philip – Wicksville – Wall – New Underwood 115 kV line
•Line is at conductor thermal limit of 90 MVA June 2011
–Special high temperature temporary jumper ratings developed for Fort Randall
•95 MVA Continuous, 124 MVA 2 hour emergency
–Installation
I t ll ti off Mi
Mission
i C
Capacitors
it
•Two 8.5 MVAR capacitors installed at Mission September 2011
4
2011 890 Study Results
Western South Dakota Near Term Issues (2011)
•Oahe Area Deficiencies
–Prior
Prior outage of 230/115 kV Auto
Auto-Transformer
Transformer
–Prior outage of Unit 1
–Prior outage of Oahe – Ash Tap
–Prior
Prior outage of Oahe – Irv Simmons
–115 kV Bus fault
•Can cause low voltages in the Pierre Area
•Can overload Oahe – Ash Tap or Oahe – Irv
Simmons lines
•Corps plans to populate existing Double
Breaker/Double Bus 115 and 230 kV bays and
install a second 230/115 kV transformer
–This
Thi fixes
fi
the
th 115 kV bus
b fault
f lt and
d the
th prior
i outage
t
issues with the Auto-Transformer and Unit 1
5
2011 890 Study Results
Western South Dakota Near Term Issues (2011)
•Oahe Area Deficiencies (cont.)
–Work
Work at Oahe Substation does not address voltage and
thermal issues caused by the prior outage either Pierre – Ash
Tap or Pierre – Irv Simmons
•An
An additional transmission line is required into the
Pierre load pocket
–Proposed solution is to abandon Ash tap and tie Ash Street
directly to Oahe providing a three separate sources to the
Pierre load pocket
6
2011 890 Study Results
Western South Dakota Near Term Issues (2011)
7
2011 890 Study Results
Western South Dakota Near Term Issues (2011)
•Rapid City Area Deficiencies
–Loss
Loss of New Underwood KV1A 230/115 kV Transformer
–115 kV Bus fault
–230 kV Bus fault
–Prior
Prior outage of New Underwood – Rushmore
–Prior outage of New Underwood – Ellsworth or Ellsworth –
Rapid City
•Can cause low voltages in the Rapid City Area
•Rapid City area improvements are planned in four
p
phases
8
2011 890 Study Results
Western South Dakota Near Term Issues (2011)
•
Phase 1 (In Service before Summer 2012):
–
•
Add additional UVLS
Phase 2 (In Service before Summer 2013):
–
–
Installation of a parallel 230/115 kV 200 MVA transformer (KV2A) at New Underwood
Installation of series bus sectionalizing breakers at New Underwood 115 kV bus between
1462 and 1562
•
•
–
Reconfiguration of New Underwood 230 kV bus
•
•
Possibly series bus sectionalizing breakers between 582 and 682
Phase 3 (In Service before 2015):
–
–
Installation of a 230/115 kV 200 MVA transformer at RCDC tie
Construction of a 115 kV RCDC-Rapid City line
•
–
•
One bus section would contain KV1A and the Rushmore line
Second bus section would contain the Ellsworth line and the Wicksville/Wall/Philip line
Possibilityy of constructing
g 230 double circuit to be determined
Potential Removal of UVLS
Phase 4 (future):
–
–
Close 230 kV loop at Rapid City DC tie
Replace existing 230/115 kV 100 MVA transformer (KV1A) at New Underwood
with a 200 MVA transformer
9
2011 890 Study Results
Western South Dakota Near Term Issues (2011)
Rapid City Area voltage issues
10
2011 890 Study Results
Western South Dakota Mid Year Issues (2012 - 2015)
Uprate Oahe – Philip Tap – New Underwood 230 kV
line
•Also identified in Keystone XL Study
•Currently limited to 240 MVA by CT settings
•New
New limit will be 320 MVA CT limit
•CT change should be completed before new Philip 200 MVA
Transformer is installed
Uprate Eagle Butte - Oahe 115 kV line
•CT tap
p change
g at Oahe ((currently
y limits to 60 MVA))
•CT tap change at Eagle Butte (currently limits to 80 MVA)
•New limit will be 104 MVA jumpers
11
2011 890 Study Results
Western South Dakota Mid Year Issues (2012 - 2015)
Uprate New Underwood – Rapid City 115 kV lines
•New
New Underwood – Rushmore – Rapid City
•New Underwood – Ellsworth
•Ellsworth – Rapid City
•Currently
C
tl lilimited
it d b
by 80 MVA CT settings
tti
•Increase rating to conductor rating
–Will require a LIDAR study
12
2011 890 Study Results
Western South Dakota Mid Year Issues (2012 - 2015)
A major rebuild of Fort Randall Substation is
planned by the Corps beginning in 2012
•Replace buswork and jumpers
•Install dedicated transformer breakers for both
230/115 kV transformers
•Targeted completion date of 2015
•High temperature jumper ratings have been
i l
implemented
t d ffor lilimiting
iti substation
b t ti conductors
d t
until rebuild is complete
–95 MVA continuous
–124
124 MVA 2
2-hour
hour emergency
13
2011 890 Study Results
Western South Dakota Mid Year Issues (2012 - 2015)
A new Lower Brule substation is planned
just outside of Big Bend on the Big Bend –
Fort Thompson line in 2013
A Lower Brule – Witten 230 kV line is also
planned
l
d
•A 200 MVA 230/115 kV transformer will be
installed at Witten
•A SPS or Generator dropping scheme will be
needed for loss of Lower Brule – Fort Thompson
•UVLS is required
q
at Keystone
y
XL PS 21 near
Gregory for the prior outage of the new 230 kV
line
14
2011 890 Study Results
Western South Dakota Out Year Issues (2016 - 2021)
• Replacement
p
of Martin 115/34.5 kV
transformer
– Required before 2021
– Sizing to be determined at a later date
• Replacement of Newell 115/69 kV
t
transformer
f
– Required before 2021
– Sizing to be determined at a later date
15
Summary of New Facilities
• Continue with Oahe improvements (completion 2015)
• Continue with Fort Randall improvements
(completion 2015)
• Construct Oahe – Ash Tap
p 115 kV line ((In service
2012)
• Uprate Oahe – Philip Tap – New Underwood 230 kV
line (2012)
• Uprate Oahe – Eagle Butte 115 kV line (2012)
• Study Nebraska Panhandle for system improvements
in 2012
• Install SPS/Generator Dropping for Lower Brule –
Witten 230 kV line (2013)
16
Action Items
• Install additional UVLS in the Rapid City Load
Pocket (Early 2012)
• Determine ROW options in the Rapid City
area for future 230 kV transmission (2011)
– Begin study based on available transmission
routes
• Study Lower Brule SPS/Generator dropping
(2012)
• Determine New Underwood 230 kV bus
arrangement (double breaker/double bus
or series bus sectionalizing breakers)
17
Questions?
18
Eastern South Dakota
19
Eastern South Dakota System Improvements
During 2011
–Installation of Eagle Area UVLS on 69 kV system
•NIPCO and MEC installed a load dropping scheme to shed load during critical
contingencies
ti
i att E
Eagle
l substation.
b t ti
•NIPCO and MEC are studying additional system improvements in the area to
reinforce the 69 kV system
–Replacement of Sioux City 161/69 kV transformer KV3A
•74
74 MVA ttransformer
f
replaced
l
d with
ith 100 MVA ttransformer
f
–Installation of a 20 MVAR reactor at Sully Buttes
•Required for the outage of Oahe – Sully Buttes
–Increased Huron – Redfield – Groton 115 kV line rating
g
•Increased from 80 MVA to 120 MVA
–Increased Watertown – Brookings #2 line rating
•Increased from 80 MVA to 120 MVA
20
2011 890 Study Results
Eastern South Dakota Near Term Issues (2011)
Ordway Area issues
↑ To Jamestown
•Ordway substation serves load
in the Aberdeen area
•Loss of Groton – Ordway
leaves Ordway load hanging
radially from Jamestown
•Can be masked in off-the-shelf
powerflow cases by waste heat
generation at Ordway and a
wind farm at Edgeley
•East
East River has added 12 MVAR
capacitors on the 69 kV system
–Were not previously modeled
•Capacitors and transmission
i
improvements
recommended
d d
21
2011 890 Study Results
Eastern South Dakota Near Term Issues (2011)
–Add a capacitor at Ordway
•Not sufficient to keep voltages at an acceptable level
as load continues to grow
•Large capacitors would only be required under prior
outage conditions
•May have to be automatically fast switched with loss of
Groton – Ordway line
•10 MVAR is suggested in combination with
transmission improvements
•Additional 10 MVAR may be required as loads
continue to increase
–Construct Ordway – Aberdeen 115 kV line
•Provides an additional source into the Ordway area
•Also helps to support the Aberdeen area for loss
of Groton – Aberdeen 115 kV line
22
2011 890 Study Results
Eastern South Dakota Near Term Issues (2011)
Sioux Falls Area Issues
•Sioux Falls 230/115 kV transformers are near the end
of their expected life span
•Breaker failure of the 230 kV bus sectionalizing breaker
results in low voltages on the 115 kV system
•Loss of one transformer can overload the second
transformer in the out year cases
•Circulating VAR/voltage set point issue between
Western’s Sioux Falls and with NSP’s Split Rock
–Sioux Falls transformers are 220/115 kV transformers
•The
The 115 kV Sioux
Sio Falls – Lawrence
La rence line is operated
normally open
23
2011 890 Study Results
Eastern South Dakota Near Term Issues (2011)
–High flows between Western and NSP load up the
230/115 kV transformer at Split Rock and the 230/115 kV
transformers at Sioux Falls
–The Sioux Falls – Lawrence 115 kV line is operated
normallyy open
p due to historical p
post contingent
g
loading
g
concerns
–Closing the Sioux Falls – Lawrence 115 kV line reduces
transformer loading
g while having
g a minor effect on net
powerflow between Western and NSP
•Power flows on both the 230 and 115 paths reducing 230/115 kV
transformer loading at both Sioux Falls and Split Rock
–Closing
Cl i th
the Si
Sioux F
Falls
ll – Lawrence
L
liline h
helps
l b
both
th
Western and NSP under prior outage conditions
–When Sioux Falls – Lawrence line is closed transformer
sizing requirements are reduced
24
Action Items
• Size Sioux Falls transformers and determine
replacement timeline
25
2011 890 Study Results
Eastern South Dakota Near Term Issues (2011)
Sioux Falls – Gavins Point Loop Issues
•Loss of either end of the loop results in low voltages
when a large amount of load is served radially
•Closing the Sioux Falls – Lawrence line helps voltages
for loss of the Gavins Point end of the loop
•A capacitor is suggested for N-1 low voltage issues
•Transmission improvements are suggested to prevent
load from being dropped under N
N-1-1
1 1 conditions
26
2011 890 Study Results
Eastern South Dakota Near Term Issues (2011)
Add 20 MVAR capacitor
bank at Spirit Mound or
Beresford substation
•Increases voltages during a
single contingency
Add Rasmussen – EJ
Manning 115 kV line
•Creates a third source into the
load pocket to increase
reliability under prior outages
•Requires the addition of a
230/115 kV transformer and a
115 kV yard at Rasmussen
•Rasmussen
R
– Vermillion
V
illi liline iis
also an option
27
2011 890 Study Results
Eastern South Dakota Near Term Issues (2011)
Replacement of Creston transformers
•Currently scheduled for 2012
•Operating guide has been created to prevent
violations until improvements
p
are completed
p
•Dedicated transformer breakers will be added when
transformers are replaced
Existing 56 MVA transformers will be replaced with
•Existing
150 MVA transformers
•Dedicated transformer breakers will be installed
•A
A 69 kV bus tie breaker will be installed
•A 69 kV capacitor will be installed
28
2011 890 Study Results
Eastern South Dakota Near Term Issues (2011)
Eagle Substation Issues
•Breaker
Breaker failure can dede
energize the entire substation
and cause low voltages on
the 69 kV system
y
•NIPCO and MEC have
installed a load dropping
scheme on the 69 kV system
•NIPCO and MEC are studying
options for additional
transmission for the 69 kV
system
t
•No Bulk Electric System
problems for these
contingencies
Large load
pocket on
networked
69kV
system
29
2011 890 Study Results
Eastern South Dakota Mid Year Issues (2012 -2015)
Replacement of Spencer
t
transformers
f
•Currently scheduled for
2013
•Dedicated transformer
breakers will be added
when transformers are
replaced
l
d
•Capacitor will be added to
the 161 kV bus
•Transformer sizing will be
finalized in a supplemental
study
Large load
pocket on
networked
69kV
system
30
2011 890 Study Results
Eastern South Dakota Out Year Issues (2016 - 2020)
• Replacement
p
of Granite Falls 115/69 kV
transformer
– Required before 2020
– Sizing to be determined at a later date
31
Summary of New Facilities
• Ordway 115 kV Capacitor (In service 2012)
• Beresford/Spirit Mound Capacitor (In service 2012)
• Continue with Creston improvements (In service
2012))
• Continue with Spencer improvements, finalize
transformer sizing (In service 2013)
• Construct
C
t t Ordway
Od
– Aberdeen
Ab d
Si
Siebrecht
b ht 115 kV liline
(In service 2013)
• Add 230/115 kV transformer at Rasmussen and
construct Rasmussen – EJ Manning (or Vermillion)
115 kV line (In service 2013)
• Size Sioux Falls transformers and determine
timeline for replacement
32
2011 South Dakota Additional Sensitivities
• Aurora
– New delivery point that relocates City of Aurora
load from Brookings to Aurora
• Roberts County
–N
New d
delivery
li
point
i t on th
the S
Summit
it – Forman
F
115
kV line
• Summit Transformer
– Verify sizing of replacement transformer
– Study combined with Roberts County request
• Fort Randal/Tyndall Voltage Support
– Additional voltage support required, especially
during Corps bird runs
– Voltages
V lt
d
drop tto 0
0.98
98 pu system
t
iintact
t t
33
Questions?
34