Wessel Bakker

Business Line Director ETD BMEA

DNV KEMA

The Netherlands

wessel.bakker@dnvkema.com

Transmission grid extension for Lake Turkana Wind Farm

Contents

Drivers for grid expansion

Suswa and Loyangalani substations

Transmission line Suswa-Loyangalani

Design aspects and features of the transmission

line

Project status

Transmission

grid Kenya

3

Grid is being

rapidly and

significantly

expanded

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

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)

Lake Turkana Wind Farm

Laisamis District

(Marsabit)

300 MW wind farm

365 Vestas V52 WTG

Connects to new

KETRACO

“Loyangalani”

220(400) kV

substation

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

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

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

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

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

Corona losses are significant

Average altitude about 1750m

Corona losses considerable

Bundle

conductors

attractive

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

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

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

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

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

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

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

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

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