Caprivi Link Interconnector - USAID SARI/Energy … Link Interconnector Presentation to SAPP Management Committee. 17 February 2010 . 03 May 2010. NamPower. 2. Contents Caprivi Link

1

Caprivi Link

Interconnector

Presentation to SAPP Management Committee

17 February 2010

03 May 2010 NamPower 203 May 2010 NamPower 2

Contents

Caprivi Link Interconnector Overview

Project Progress

Effect of HVDC Link on AC Networks

03 May 2010 NamPower 3

Caprivi Link Interconnector

Gerus

HwangeVictoria Falls

Sesheke

Kafue Gorge

Zambezi

Auas

LegendHVDC330 kV220 kV400 kV

Namibia

Zambia

Zimbabwe

Botswana


Namibian Network

Gerus

Otjikoto

Auas

Hardap

Omatando Rundu

Omburu

Namib

Obib

Walmund Van Eck Omaere

Ruacana

Paratus

Harib

OkatopeLivingstone(ZAMBIA)

Ghanzi

280 km

950 km

Zambezi

Legend400 kV330 kV220 kV132 kVHVDC

KuisebBotswana


The objective of the Caprivi Link Interconnector is to provide an asynchronous link between the Namibian and Zambian/Zimbabwean electricity networks in order to ensure a reliable power transfer capability between the east and west of the South African Power Pool (SAPP)

Purpose of Scheme


Connection of Zambezi substation to the rest of the NamPower grid

Better utilisation of the Livingstone – Zambezi 220 kV line that was constructed by ZESCO & NamPower

Provide and alternative wheeling path for SAPP electricity trade

Benefits of Scheme


Phase 1: 300MW Monopole HVDC Scheme (2010) 300MW, 350kV dc monopole converters using VSC technology

connecting to 330kV ac at Zambezi substation and 400kV ac at Gerus substation

950km DC overhead line with both pole conductors installed

AC substation extensions:Zambezi: 2 x 220/330kV 315 MVA transformersGerus: 2 x 220/400kV 315 MVA transformers

Phase 2: Upgrade to 600MW Bipole HVDC Scheme Second 300MW, 350kV dc monopole

330kV ac network strengthening Zambia/Zimbabwe

400kV ac line Auas - Gerus

Phases


Components of Scheme

6

5

21 3Zambezi

Substation

AC Line

DC Line Converter Station 330/220kV AC Station4 1GerusSubstation

Converter Station400/220kVAC Station

& Line Feeder

400kV Line FeederAuas

Rundu

Katima Mulilo

Otjikoto

Gerus

Zambezi


Active power control

AC voltage control at both ends (SVC operation)

Power oscillation damping (not used)

Subsynchronous resonance (SSR) damping

Operation with reduced DC voltage

Overload capability to 350 MW

Control Features


Normal power transfer in both directions

Passive/Islanded network at Gerus or Zambezi – HVDC scheme does frequency control of separated network

Energisation of a black network from remote station

Metallic return and earth return

Modes of Operation


350kV HVDC Line Completed November 2009

AC Substation Extensions: Gerus and Zambezi Equipment installation 98% complete

Busbars and stringing is complete

2 x 315MVA coupling transformers installed

Busy with commissioning

Energisation of first 315MVA transformers planned for early March 2010

Project Progress


Project Progress

HVDC Converter Stations Civil works 98% complete

Installation 65% complete

AC yard equipment and AC filters installed

3 x single phase converter transformers installed

Busy with installation of valves, converter reactors, AC hall, DC hall and DC yard equipment and cabling

Energised testing & transmission tests from end-March to end-May 2010

Earth electrodes installation planned for Sept./Oct. 2010 (scheme will be operated in metallic return initially)


Project Progress – HVDC Line


Project Progress – AC Substations


Project Progress – Zambezi Site


Project Progress – Converter AC Hall


Project Progress – Converter Valve Hall


Project Progress – Converter Trafos


Project Progress – Converter AC Filters


Extensive studies done to optimise HVDC controls and check for AC network stability

Effect of AC network faults

Effect of DC line faults

Power oscillations

Subsynchronous torsional interaction (SSTI)

Frequency control in islanded networks

Extensive verification of actual control & protection systems done with RTDS model in factory

Effect of HVDC on AC Networks



Power Control The power can be precisely controlled in the HVDC link from 0 –

300MW (Phase 1).

Initially a maximum power transfer of 150MW is expected due to limitations in the connected AC networks

Balance of power will flow in AC networks according to impedances and phase angle differences

AC Voltage Control at Terminals (SVC Operation) AC voltage control available in conjunction with active power transfer

Provides voltage stability to connected AC networks

±100 MVAr available at terminals throughout 0 – 300 MW range




Harmonics Harmonics generated by converter stations may not exceed 50% of

allowable maximum levels (NRS)

All envisaged AC network configurations and realistic contingencies included in AC network harmonic impedance representation

Use of PWM in a voltage sourced converter allows “selected” harmonics to be suppressed.

For Caprivi OPWM is used which cancels harmonics of order 5, 7, 11, 13, 15, 17, 19, 23, 25, 29

Filters tuned to 3rd, 32nd and 60th harmonics are installed



Frequency Control of Islanded Networks E.g. Northern Namibian network separated from southern network

(connected to Eskom)

HVDC can control frequency in northern network by control of active power into the network

Black Start Capability A VSC HVDC converter can be energised from the other converter

station

The newly energised converter can then feed into a previously blacked-out network



Gerus

Otjikoto

Auas

Hardap

Omatando Rundu

Omburu

Namib

Obib

Walmund Van Eck Omaere

Ruacana

Paratus

Harib

OkatopeLivingstone(ZAMBIA)

Ghanzi

280 km

950 km

Zambezi

Legend400 kV330 kV220 kV132 kVHVDC

KuisebBotswana



Single phase to earth fault with successful ARC on Zambezi - Sesheke 220kV line: Present network (2010)

100MW transfer from Zambezi to Gerus through HVDC link

Single phase to earth fault on Zambezi – Shesheke 220kV line

Cleared by zone 1 protection, ARC in 1.2s

AC Line Fault, successful ARC


1ph-e fault Zambezi–Shesheke, succ ARC

0 0.5 1 1.5 2 2.5 3 3.5 4-400

-300

-200

-100

0

100

200

300

400

UPC

C_L

1_P

RIM

SID

E [k

V]

UPC

C_L

2_P

RIM

SID

E [k

V]

UPC

C_L

3_P

RIM

SID

E [k

V]

File: S1WMNN100I11ZB_TFR CL_S1PCP1A1 1 20091029 12;43;51_829000.CFG

0 0.5 1 1.5 2 2.5 3 3.5 40

0.05

0.1

0.15

0.2

0.25

0.3

0.35

P_P

CC

Y [p

u]

0 0.5 1 1.5 2 2.5 3 3.5 4-0.5

-0.4

-0.3

-0.2

-0.1

0

0.1

0.2

Q_P

RIM

SID

E [p

u]

Time [s]

Power p.u. on 350MW base

Reactive Power p.u. on 350MVAr base

Zambezi primary voltage (kV)


1ph-e fault Zambezi–Shesheke, succ ARC

0 0.5 1 1.5 2 2.5 3 3.5 4313.6

313.8

314

314.2

314.4

314.6

w_R

uaca

na [R

ad/s

ec]

0 0.5 1 1.5 2 2.5 3 3.5 4313

314

315

316

317

318

w_v

icFa

lls [R

ad/s

ec]

File: RTDSWMNN100I11ZB_rtdsPlots.cfg

0 0.5 1 1.5 2 2.5 3 3.5 430

40

50

60

70

80

PM

AC

H_V

icFa

lls [M

W]

0 0.5 1 1.5 2 2.5 3 3.5 4280

290

300

310

320

PM

AC

H_R

uaca

na [M

W]

Time [s]


DC Line Fault, successful clearing

DC line fault (pole to earth) at midpoint of DC line with successful fault clearing: Present network

100MW transfer from Zambezi to Gerus

DC line fault clearing sequence

Converter AC breakers opened

DC pole breakers and high speed switches opened

Active power transmission resumed ~900ms after fault



0 0.5 1 1.5 2 2.5 3 3.5 4-0.1

0

0.1

0.2

0.3

0.4

P_P

CC

Y [p

u]

0 0.5 1 1.5 2 2.5 3 3.5 4-500

0

500

UPC

C_L

1_P

RIM

SID

E [k

V]

UPC

C_L

2_P

RIM

SID

E [k

V]

UPC

C_L

3_P

RIM

SID

E [k

V]

File: S1WMNN100M35DA_S1PCP1A1 1 20091124 20-23-10_494000.CFG

0 0.5 1 1.5 2 2.5 3 3.5 4-0.1

-0.05

0

0.05

0.1

0.15

0.2

0.25

Q_P

RIM

SID

E [p

u]

Time [s]


Reactive Powerp.u. on 350MVAr base




0 0.5 1 1.5 2 2.5 3 3.5 4312

313

314

315

w_R

uaca

na [R

ad/s

ec]

0 0.5 1 1.5 2 2.5 3 3.5 4310

312

314

316

318

w_v

icFa

lls [R

ad/s

ec]

File: RTDSWMNN100M35DA_rtdsPlots.cfg

0 0.5 1 1.5 2 2.5 3 3.5 40

20

40

60

80

PM

AC

H_V

icFa

lls [M

W]

0 0.5 1 1.5 2 2.5 3 3.5 4240

260

280

300

320

PM

AC

H_R

uaca

na [M

W]

Time [s]


DC line fault (pole to earth) at midpoint of DC line with unsuccessful fault clearing: Present network

100MW transfer from Zambezi to Gerus

DC line fault clearing sequence

Converter AC breakers opened

DC pole breakers and high speed switches opened

Reclose attempt, second clearing sequence

DC line isolated but converter AC breakers closed

SVC functionality available after fault

DC Line Fault, unsuccessful clearing



0 0.5 1 1.5 2 2.5 3 3.5 4-0.2

-0.1

0

0.1

0.2

0.3

0.4

0.5

P_P

CC

Y [p

u]

0 0.5 1 1.5 2 2.5 3 3.5 4-500

0

500

UPC

C_L

1_P

RIM

SID

E [k

V]

UPC

C_L

2_P

RIM

SID

E [k

V]

UPC

C_L

3_P

RIM

SID

E [k

V]

File: S1WMNN100M37DA_S1PCP1A1 1 20091124 20-43-16_329000.CFG

0 0.5 1 1.5 2 2.5 3 3.5 4-0.1

-0.05

0

0.05

0.1

0.15

0.2

0.25

Q_P

RIM

SID

E [p

u]

Time [s]


Reactive Powerp.u. on 350MVAr base




0 0.5 1 1.5 2 2.5 3 3.5 4313

313.5

314

314.5

315

w_R

uaca

na [R

ad/s

ec]

0 0.5 1 1.5 2 2.5 3 3.5 4310

312

314

316

318

w_v

icFa

lls [R

ad/s

ec]

File: RTDSWMNN100M37DA_rtdsPlots.cfg

0 0.5 1 1.5 2 2.5 3 3.5 40

20

40

60

80

PM

AC

H_V

icFa

lls [M

W]

0 0.5 1 1.5 2 2.5 3 3.5 4150

200

250

300

350

PM

AC

H_R

uaca

na [M

W]

Time [s]


Power Oscillations Studies done to check power oscillations between HVDC controls and

nearby generation after network disturbances

It was found that oscillations are sufficiently damped

POD function available in HVDC controls but not activated

SSTI Hydro generators not at risk

Possible interaction with thermal generators

Screening study done to check for risk of SSTI using Unit Interaction Factor (UIF) method

Hwange not at risk, Van Eck may be at risk for 600 MW scheme, further studies being done

Power Oscillations and SSTI


Caprivi Link Interconnector

Thank you for your attention!

Documents

Caprivi Link Interconnector - USAID SARI/Energy … Link Interconnector Presentation to SAPP Management Committee. 17 February 2010 . 03 May 2010. NamPower. 2. Contents Caprivi Link