THE NELSON RIVER BIPOLE 1 HVDC SCHEME

 

Between:      Radisson near Gillam and Dorsey near Winnipeg, Manitoba.

 

Power Co:     The Manitoba Hydro-Electric Board, Manitoba Canada

 

Manufacturer: GEC ALSTHOM. (English Electric), England.

 

Commissioned: 1973.

 

Main purpose: Bulk power supply from isolated hydro-electric generation in the north to a large load center in the south. No power flow from south to north is required. The system is run on a varying daily load cycle.

 

Main data:    Bipole, 1854 MW at the rectifier at ± 463.5kV DC and 2000 A

              Overload capacity : (short term) : 10%

              The convertors of one pole (Pole 1) now uprated to 500kV continuously.

 

A.C. Networks:

              At each terminal, three single phase convertor transformers with tertiary windings are used for each of the three 6-pulse convertor units per pole. The tertiary windings at Dorsey supply the synchronous compensators.

 

              Radisson :

              Transformers : 341 MVA, 138 kV + 20%

                                            -  7% / 134kV

                                              (three phase)

              connected to the 138kV AC system.

              AC Filters:2x(5,7) and one 11,13 and HP.

 

              Dorsey :

              Transformers :323 MVA,230 kV + 28%

                                           - 7%/134kV/17kV

                                              (three phase)

              connected to the 230kV AC system

 

              Synchronous Compensators:

              Six at    + 160 Mvar capacitive,

                        -  80 Mvar inductive,

              connected to the 17kV tertiary

              A.C. Filters : 2 x (5,7,11,13 and HP).

 

 

 

 

HVDC System:  Route length = 890 km

 

              Overhead lines : Conductors : ACRS ; Duplex 974,3 mm2

              (each 1.6" dia. 1843.2 MCM 72/7)

              457,2 mm (18") sub spac. 3600 amps/pole

              DC resistance/pole is 13.89 ohms at 20° C

              Shielding : 34.93 mm (1 3/8") dia., 7 Strand Grade 180 steel

              Towers : Tangent and light angle guyed single mast dead end towers of the self-supporting type.

              Insulator creepage: 2.3 to 2.35 cm/kV.

 

Electrodes:   Radisson : It is located 11.2 km from the station and is of the ring type 305 metres in diameter. It comprises a steel rod and is installed in a low sulphur coke bed.

              Resistance : 0.16 - 0.37 ohms.

 

              Dorsey : It is located 21.9 km from the station and is of the ring type 305 metres in diameter. It comprises a steel rod and is installed in a low sulphur coke bed.

 

              Resistance : 0.37 to 0.6 ohm.

 

              The Dorsey electrode is designed to accomodate both Bipoles 1 and 2.

 

              Electrode line : ASCR, 2 - 795 MCM, 54/7. This is mounted on a separate wood pole structure.

 

D.C. Filters: Each pole has one sixth and one twelfth harmonic filter. The filters are connected between the pole and the electrode line.

 

HVDC valves: In pole 2 mercury arc valves are used. Each valve has air-cooled anodes and a water-cooled cathode.

 

              There are six anodes per valve. Six valves and a bypass vacuum switch form a 6-pulse convertor unit at 150kV (nominal).

 

              In pole 1 thyristor valves have replaced the mercury-arc valves in all three valve groups of this pole only (1992-3). Three thyristor double valves are installed in each 6-pulse group.

 

              The replacement involved only the valves and the valve group control system. The original building, switchgear, wall bushing and transformers are retained.

 

 

              The valves at Radisson each contain 84 series-connected thyristors, three of which are redundant. The valves at Dorsey have 80 series-connected thyristors, again with three redundant.

 

              The valves are cooled by circulating a mixture of water and ethylene glycol and is a single circuit arrangement without intermediate heat exchangers. Each valve is protected from overvoltage by a parallel-connected gapless metal oxide surge arrester.

 

              The upper levels of control hierarchy (Pole Control and Master Control) remain unchanged, but all control and specialised protection equipment below Pole Control has been replaced.

 

              The replacement convertors and associated equipment are capable of operation at up to 500kV, but operation at this voltage is limited at present by other DC equipment.

 

              Each pole has three series connected 6-pulse convertor units. The smoothing reactors are placed on the high voltage side. There are two smoothing reactors per pole per station with the DC filters between them. The smoothing reactors are 0.5 Henry each.

 

A.C. Filters: Both terminals for bipole are provided with harmonic filters :

 

              Dorsey : 2 filters each for :

 

Harm.

 MVAr

 C=µF

 L=mH

 R=ohm

5.

  34.7

  1.67

 168

   3.17

7.

  17.3

  0.852

 168

   4.43

11.

  26.3

  1.31

  44.4

   1.84

13.

  18.8

  0.938

  44.4

   2.17

HP.

  80.6

  4.04

   4.07

  42

 

              Total reactive power installed = 350 MVAr

 

 

              Radisson : 2 x (5,7) + 2(11,13) + 1 HP

 

Harm.

 MVAr

 C=µF

 L=mH

R=ohm

5.

 34.23

  4.58

  61.4

   1.08

7.

 17.12

  2.34

  61.4

   1.52

11.

 27.8

  3.84

  15.2

   0.75

13.

 19.84

  2.75

  15.2

   0.89

HP.

 79.11

  11

  1.45

  21

 

              Total reactive power installed = 230 MVAr

 

 

 

 

 

 

Reference:

              1 - BATEMAN L.A., BUTLER L.S., HAYWOOD R.W.

              The ± 463.5 kV Direct Current Transmission

              System for the Nelson River Project. (CIGRE

              1968 Session, Paper No. 43-02).

 

              2 - ESTEY D.S., HAYWOOD R.W., ROLLAND J.W.,

              WILLIS D.B. : Nelson River HVDC System

              Commissioning and Initial Operating

              Experience      (CIGRE 1974 Session Paper

              No. 14-02)

 

              3 - "ELECTRA" No 63 (1979)

              "AC Harmonic Filter and Reactive

              Compensation for HVDC".

              A general survey by SC 14 - WG03.

 

              4 - CIGRE 1984, Paper 14.04

              "Responses of The Nelson River HVDC System

              to Disturbances on the Receiving End AC

              Network" by SC14 : R.W. HAYWOOD and J CHAND.

 

 

System correspondent :

 

 

              Dr Mohamed M Rashwan

              Manager

              HVDC Operations Department

              Dorsey HVDC Station

              Rosser, Manitoba

              R0H 1EO

              Canada

 

              Tel: +1 (204) 453 1313

              Fax: +1 (204) 453 1810