transmission grid extension for lake turkana wind farm bakker tues t... · transmission grid...
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Wessel Bakker
Business Line Director ETD BMEA
DNV KEMA
The Netherlands
Transmission grid extension for Lake Turkana Wind Farm
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Contents
Drivers for grid expansion
Suswa and Loyangalani substations
Transmission line Suswa-Loyangalani
Design aspects and features of the transmission
line
Project status
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Transmission
grid Kenya
3
Grid is being
rapidly and
significantly
expanded
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Drivers for 220/400 kV grid
extension West of Nairobi
Expected high demand growth in Kenya
Planned extension of geothermal generation at
Olkaria and other sites
Planned Lake Turkana Wind farm
Connection point for Ethiopian HVDC
interconnector
KPLC/KETRACO planned for a new 400/220kV
substation near Mount Suswa, also as part of the
Nairobi Ring project
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Suswa substation
1,5 breaker design
1 reactor bay
2 capacitor bank bays
14 line bays
Central control building
Focus on high reliability
Space for extension
(HVDC)
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Lake Turkana Wind Farm
Laisamis District
(Marsabit)
300 MW wind farm
365 Vestas V52 WTG
Connects to new
KETRACO
“Loyangalani”
220(400) kV
substation
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Grid connection of LTWP/Rift
Valley: Loyangalani-Suswa
transmission line
KPLC/KETRACO planned for a transmission line
from the new Suswa substation to Loyangalani:
Connection of Lake Turkana Wind Farm
Connection of geothermal power plants in the
Rift Valley
Strengthening the distribution grid and rural
electrification of the Rift Valley along the route
Ethiopia HVDC to terminate at Suswa
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Development of the transmission
line and substations
As the first party to be connected to the line,
LTWP, together with KPLC, KETRACO and the
Ministry of Energy, have started to develop the
Loyangalani and Suswa substations and the
transmission line up to tender evaluation
KETRACO have taken over the lead and
contracted the substations and the transmission
line
DNV KEMA supported as owners engineer
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Design considerations for
transmission line and
substations
The Kenya grid may not survive 300 MW trip on
an outage
Hence, the substations are fully redundant with
1½ breaker systems
Also, the transmission line was designed as a
double-circuit line with proper mechanical safety
factors and good lightning performance
Specific attention to loss optimization
Specific attention to lightning performance
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Transmission line: features
428 km length double-circuit transmission line
for full redundancy with steel lattice towers,
composite insulators and ACSR conductors
Design rating 400 kV, initial operation at 220 kV
proposed (same was applied to Mombasa line)
Double OPGW for maximum communication
redundancy
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Loss optimization study
Ohmic losses
Corona losses
Conductor configurations:
3 x 315 mm2 4 x 315 mm2
3 x 400 mm2 4 x 400 mm2
2 x 560 mm2 3 x 500 mm2 4 x 500 mm2
2 x 710 mm2
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Corona losses are significant
Average altitude about 1750m
Corona losses considerable
Bundle
conductors
attractive
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Economic analysis
Cost model for transmission line to account for
differences in conductor, insulator, tower and
foundation costs between the conductor
configurations
Sensitivity analysis for moment to switch to 400
kV operation after 3, 7 and 25 years
Capitalized cost of losses at 8%/a interest rate
Time period 25 years
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400 kV operation after 7 years
0
50
100
150
200
250
2 x560
2 x710
3 x315
3 x400
3 x500
4 x315
4 x400
4 x500
USD Initial investment
Capitalized losses
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400 kV operation after 25 years,
i.e. operation at 220 kV
0
50
100
150
200
250
2 x560
2 x710
3 x315
3 x400
3 x500
4 x315
4 x400
4 x500
USD Initial investment
Capitalized losses
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400 kV operation after 3 years
0
50
100
150
200
250
2 x560
2 x710
3 x315
3 x400
3 x500
4 x315
4 x400
4 x500
USD Initial investment
Capitalized losses
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Observations
If the transmission line remains operated at 220
kV, the 2-bundle conductors lead to lowest
evaluated costs; however, a conversion to 400
kV would be prohibitively expensive due to
excessive corona losses
In the other cases, the 3x400 mm2 configuration
is most economic
As 400 kV conversion is assumed to take place
in foreseeable future, 3x400 mm2 was chosen
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Lightning performance
Double-circuit outages due to back flashover are
to be avoided
Soil resistivity and tower footing resistance
expected to be high at some places
Lightning performance specified in EPC contract
Still, a detailed ATP simulation study was carried
out on a preliminary tower design in order to
determine up-front the feasibility of the functional
requirements
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Lightning performance (2)
Asymmetric insulation in order
to have one “strong” circuit rarely
experiencing back flashovers
Shielding failures are negligible
Switching transients acceptable
The back flashover performance
was shown to be OK provided the
tower footing resistance is low
enough
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Status
Contracts for the substations have been closed
Suswa 220 kV substation under construction,
completion expected in May 2014
Loyangalani 220(400) kV substation contracted,
Notice to Proceed expected Fall 2013 (at Financial
Close of LTWP), completion expected Summer 2015
400 kV Transmission line contracted, Notice to
Proceed expected Spring 2013, completion
expected Spring 2015
20
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