Transcript Managing West Texas Wind

Managing West Texas Wind
SWEDE 2008 Conference
May 2, 2008
Presented by Paul Hassink
AEPSC Texas Transmission Planning
The State of West Texas Wind
• Abundance of wind energy in Texas is so great that
the State of Texas goal of 10,000 MW for 2025 will
be achieved with Wind that is already committed
• Public Utility Commission (PUCT) proceeding on
Competitive Renewable Energy Zones (CREZ) set
out scenarios of 12 GW, 18.5 GW, and 25 GW of
West Texas wind production
• On April 2, ERCOT’s report on CREZ Transmission
Optimization (CTO) Study recommended a 345 kV
plan to meet the PUCT request
• A minimum of five years is needed just to begin
implementation of the extensive transmission plan
resulting from the CREZ proceeding
ERCOT Recommended
CREZ Plan for 18.5 GW
(6.9 GW existing)
2.4GW
3.2GW
PUCT
CREZ
4.1GW
1.9GW
Synergies between Load and Wind
• Until the CREZ lines are ready to transport the wind,
AEP Texas must continue to serve load, while
addressing wind
• On the AEP Texas system, most wind farms are
interconnected to the 138 kV and 69 kV systems
• These 138 kV and 69 kV systems, when built, were
intended to support only 10’s of MW of load
• In order to connect wind farms faster and with less
impact to land owners, existing lines provide paths
for wind and an opportunity for system upgrades
• AEP Texas customers benefit from improved service
from upgraded lines, and ERCOT customers benefit
from more wind energy delivered sooner
Solutions Gleaned from Experience
• Path Reinforcement such as the rebuild or
reconductor of lines
• Voltage Regulation at 69 kV near the load
• Isolation of load serving lines from generation
serving lines
• Power flow Redirection via technologies such as
phase shift transformers and series reactors
Path Reinforcement
• With over 1000 MW of Wind interconnected to the
Abilene to San Angelo 345 kV line, additional
transmission capacity is necessary to deliver wind
production to ERCOT major load centers,
particularly DFW
• Opening existing 345 kV and 138 kV lines to rebuild
them would cause severe congestion
• Local 69 kV lines are in need of upgrades and can
be rebuilt to provide new 138 kV paths to export
wind energy
• Upgrading existing 69 kV lines improves reliability to
customers and minimizes impact to land owners
Path Reinforcement
69 kV lines to be Rebuilt to
Double Circuit serving Load
at 69 kV and Wind at 138 kV
Voltage Regulation at 69 kV
• Dynamic Reactive Compensation
– Minimizes the frequency of shunt capacitor
switching
– Applies dynamic resource at load to mitigate the
magnitude of voltage flicker
– Distributes dynamic requirement for stability
enhancement
• Standard Configurations
– 69 kV +/- 25 MVAR dynamic reactive with 138 kV
28.8 MVAR shunt capacitor bank
– 69 kV +/- 50 MVAR dynamic reactive with 138 kV
57.6 MVAR shunt capacitor bank
Reactive Compensation Configuration
138 kV
28.8/57.6 MVAR
69 kV
+/- 25/50 MVAR
138 kV 57.6 MVar capacitor bank
with +/- 50 MVAR dynamic
reactive compensation @ Crane
McCamey Area
Distributed Dynamic
Reactive Resources
King Mountain
Indian Mesa
Desert Sky
Woodward
Sherbino
138 kV 57.6 MVar capacitor bank
with +/- 50 MVAR dynamic reactive
compensation @ McCamey
TNC 69kV
TNC 138kV
Foreign
LCRA JDA
TNC Sub
Wind Farm
LCRA JDA
Reactive Device
138 kV 28.8 MVar capacitor bank
with +/- 25 MVAR dynamic
reactive compensation @ Ozona
Isolation and Redirection
• With almost 7000 MW of West Texas wind
production committed by the end of 2009, the
overloads of the 138 kV and 69 kV lines west of
Abilene and San Angelo will become routine
• By separating wind generation from the 138 kV and
69 kV lines that cross the interface between West
Texas and ERCOT load centers, power can be
forced to flow on the 345 kV system
• Additionally, Phase Shift Transformers can buck the
power flow on 138 kV lines by increasing the power
angle across the lines
Isolation and Redirection
345 kV Export Path
Split Busses in Substations
Isolate Wind from Load and
route wind to 345 kV system
Big Lake
Abilene
San Angelo
345 kV
Export
Path
Phase Shift Transformers
block power flow from
weaker transmission systems
Improved Reliability with
Increased Wind Production
• Interconnecting wind generation well in excess of local
load places the load serving transmission system at risk
• While the CREZ plan will alleviate the problem, it is at
least five years away
• Separation of wind generation from load serving lines
and the redirection of power flow to the bulk transmission
system can buy time until CREZ lines are completed
• In the mean time, it makes sense to upgrade the
capacity of the existing system, where there is a benefit
to reliability
• Rebuilding 69 kV lines and adding dynamic reactive
compensation improve service to customers, and
increases transmission capacity for wind energy
Path Reinforcement
•
Double Circuit 138/69 kV Lines (existing 69 kV lines with numerous load
serving substations)
– Upgrades existing 69 kV lines with a trunk 138 kV circuit (second circuit) relieves
the need to convert multiple small 69 kV substations and routes power from
generation around the constraining 69 kV line
– Eliminates the need for a new right of way and potentially reduces overall
footprint with less structures and single pole (as opposed to existing H-frame)
designs
•
ACCC Conductor (138 kV, composite core trapezoidal stranding)
– High temperature ACCC conductor can double the rating of an existing 138 kV
line in less than 6 months at a fraction of the cost of rebuilding the line
– Existing line must have significant remaining life
•
Line Tension Monitors (345 kV and 138 kV, real time rating)
– Since wind typically achieves its highest capacity during mild ambient conditions,
a significant amount of line capacity above the static rating is available when
significant amounts of power are exported
– Day-ahead planning can estimate line capacity based on anticipated line MOT
due to forecasted ambient temperature and cooling of wind correlated to wind
production, enabling additional line capacity
Isolation of Load from Generation
•
Sectionalizing 69 kV systems (normally open motor operated switches with
RTU control and load break capability)
– Blocks power flow on parallel 69 kV lines at the expense of radial operation
– Mitigated by additional parallel transformation, which provides backup to 69 kV
systems dependent on a single autotransformer
•
Bus Splitting (345 kV and 138 kV, double bus or in-line bus breakers)
– Substation designs or reconfigurations that provide the flexibility to isolate
through path wind generation lines from load serving lines with normally open
breakers
•
Line Bypass (345 kV and 138 kV, line rerouting outside of substations)
– Applications where flexibility is not needed, lines can be rerouted around
substations to provide an express path for generation and balance power flow
•
Attaching IPPs to Spare Circuits (345 kV and 138 kV, double circuit lines
with an empty position)
– Overload of the line/path can be relieved by connecting IPPs to a new circuit on
an empty position of an existing or rebuilt line, and moving the point of
connection to the grid to a substation with adequate interconnection to the bulk
system
Power Flow Redirection
•
Phase Shift Transformers (138/138 kV PST, 150/200 MVA, +/- 30 degrees,
in-line LTC, with bypass breaker)
– Many of the underlying 138 kV lines cannot be rebuilt without extensive rebuilds
that extend down stream into other 138 kV systems, so a PST can applied to
block 138 kV power flow from wind generation, diverting the power to the 345 kV
system
•
Series Reactors (138 kV / 300 MVA and 69 kV / 100 MVA, 10-20 ohms, with
bypass breaker)
– Similar to PST, but for applications with less sever overloads and that are not
voltage constrained
•
Series Capacitors (345 kV, 0.03 pu, 2000 MVA, segmented)
– Redirects power from constrained 345 kV lines to 345 kV lines with reserve
capacity, thereby relieving constraints at 345 kV and improving stability