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THE INGA SHABA HVDC SCHEME

 

 

 

 

Between:           The provinces of Inga and Shaba in the republic of ZAIRE.

 

Power Co.:    Societé Nationale d'Electricité Kinshasa, ZAIRE

 

Manufacturer:

              Morrison-Knudson Co, USA, as main contractor with ASEA, Sweden and G.E., USA as subcontractors for the two converter stations.

 

Commissioned: 1982/1983

 

Main purpose: Bulk power transmission for electricity supply to KOLWEZI in the region of Shaba, the mining district of south east Zaire.

 

Main data:    First stage: 560 MW at ± 500 kV D.C. and 560 A/pole

 

              Overload capacity:

         35% for 30 min.

 

A.C. networks:

              At both terminals 6 single phase converter transformers are used per 12 pulse converter unit.

 

Inga :

7 MVA, 220 kV + 15/ - 10 kV/225 kV, 50 Hz zH

 

The transformers are connected to the 220 kV A.C. busbar.

Short circuit capacity = min. 2930 MVA

 

Kolwezi:

              51 MVA. 220 kV + 24.5/ - 21.0 kV/192 kV,50Hz

 

The transformers are connected to the 220 kV A.C. busbar.

 

Further more three 70 MVA synchronous condensers are connected to the busbar.

 

Short circuit capacity = min. 1690 MVA.

 

 

 

HVDC System:  Route length = 1700 km.

 

              Overhead lines: Designed as two separate lines with conductors = 3 x 524 mm2 ACSR (1033 MCM)

 

              The lines are separated 40 m from each other.

 

              Line towers: These are self supporting lattice steel structures.

 

              Shieldings: The overhead lines are shielded by a 520 mm2 ACSR (1018 MCM).

 

              Insulator leakage: 2.67 cm/kV at 500 kV D.C.

 

              Electrodes :  The electrode stations as well at Inga as at Kolwezi are located in a distance of 39 km and 11 km respectively from the converter stations, and both are designed as land electrodes.

 

              Resistance     Inga:    0,24 ohms

                     Kolwezi: 0,14  ohms

 

              The Inga electrode is designed as a linear ground electrode and the Kolwezi electrode is a three-legged ground star electrode

 

D.C. Filters: No D.C. filters are used.

 

HVDC valves:  Air cooled thyristor valves are used. They are designed as double valves, fully insulated to ground in order to obtain the possibility of changing the polarity. Six double valves/pol/form a 12 pulse converter unit.

 

              One valve arm has 43 active modules, each with 6 series connected thyristors giving the total of 258 thyristors in series connection per valve arm. This makes 516 thyristors per valve structure or 3096 thyristors per 12 pulse converter unit for 500 kV D.C. and 560 A.

 

              The valve structure is air insulated.

 

              The D.C. reactors are placed on the neutral side and they are designed for 1.5 H at 560 A. As protection against incoming lightning surges reactors are placed on the high voltage side. These are designed for 0.075 H at 560 A.

 

 

A.C. Filters: Harmonic filters are provided at each terminal and designed as two combined 11. - 13. harm. and HP filters each with:

 

              Inga: total installed 37.2 x 2 MVAr.

 

       

Harm.

MVAr

C=µF

L=mH

R=ohm

  11.

  10.1

 0.664

 126

   3.0

  13.

   7.2

 0.474

 126

   3.6

  HP

  19.9

 1.31 

  13.4

 283

 

 

 

        

              Kolwezi: total installed 95.2 x 2

       

Harm.

MVAr

C=µF

L=mH

R=ohm

  11.

  28.1

  1.85

  45.3

   1.1

  13.

  20.4

  1.32

  45.3

   1.3

  HP

  47

  3.09

   5.7

 164

 

 

 

     

        

References:   Electra no. 63 (1979)

              "A.C. Harmonic filter and reactive compensation for HVDC"

              A general Survey by SC14 - WG03.                                               

 

 

Systeme correspondent :

 

Mr Mutanda Ngoy Muana

C/O MKI-CIS

P.O. Box 7808

Boise, Idaho 83729

USA

 

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