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THE KONTI-SKAN HVDC SCHEME

 

 

 

 

Between :     KONTI-SKAN 1 : Denmark (V. Hassing) and Sweden (Gothenburg)

              KONTI-SKAN 2 : Denmark (V. Hassing) and Sweden (Lindome)

 

Power Co:     The  Jutland-Funen  Power  Pool ELSAM, Fredericia and Swedish National Grid, Stockholm Sweden

 

Manufacturer: ASEA Transmission , Sweden

 

Commissioned: Konti-Skan 1 :10th of September 1965

 

              Konti-Skan 2 : 1st of November 1988, after three months of trial operation

 

Main purpose:

              Konti-Skan 1 :Peak power reserve for both countries. Excess power supply.

              Energy supply during emergency situations to support the AC system in both countries in case of network disturbances.

 

              Konti-Skan 2 : Interconnection between two large asynchronous AC systems. Emergency energy supply for supporting AC systems during network disturbances in both countries.

              Energy exchange and peak power reserve for both countries.

 

Main data:   

              Konti-Skan 1 : Monopole : 250 MW ± 250 KV DC and 1000 A. Earth return with the anode situated on the Danish side. (DC current flows always  in the  direction Sweden - Denmark).

              Overload capacity : 10% continuously.

 

              Konti-Skan 2 : Monopole 300 MW at ± 285 kV DC and 1050 A . Overload capacity (with redundant cooling system in operation) :

              continuously : 10 %

              continuously : 410 MW at t <5° C (37 %).

 

              Earth return, however also with a kind of bipole operation with individual pole control of KS 1 and KS 2. The system has been designed with an anode electrode station also on the Swedish coast.

 

             

 

             

AC Networks: 

              Konti-Skan 1 (KS1) : At both terminals one 3-phase converter transformer/6-pulse converter unit is used.

 

              Denmark:

              a) one 154 MVA, 165 15%/111/12 kV, 50 Hz, with a synchronous condenser (100 MVAr) connected to the tertiary winding at 12 kV.

 

              b) one 154 MVA, 165 ± 15%/111 kV, 50 Hz.

             

              Both transformers are connected to the 150 kV AC system.

 

              Short circuit capacity : min. 2500 MVA

 

              Sweden:

              Two 154 MVA, 139/111 kV, 50 Hz. Both transformers are connected to the 130/400 kV AC system. No tap changers are used on the Swedish transformers.

 

              Short circuit capacity : min. 6500 MVA

 

              Konti-Skan 2 (KS2) : Two 3-phase converter transformers are installed in each terminal.

 

              Denmark:

              173 MVA, 410 ± 12 x 1.25 %/115 kV,50 Hz.

 

              Short circuit capacity : min : 1200 MVA

              (normal AC network). Extreme min :  900 MVA

              (random but possible).

 

              Sweden:

              173 MVA, 410 ± 11 x 1.25 %/115 kV,50 Hz

 

              Short circuit capacity : min : 1000 MVA

              (normal AC network). Extreme min :  600 MVA

              (random but possible).

 

 

 

 

 

HVDC System:       Konti-Skan 1 :

                       

              Route length: Approx. 180 km.

 

              Overhead lines: Length in Denmark: 34 + 17 km. (17 km on the island of Laesoe), length in Sweden: 40 km.

 

 

 

 

 

             

              Line towers : In Denmark self supporting lattice steel structures are used.

              In Sweden guyed lattice aluminium structures are used and in angle towers, self supporting lattice steel structures are used.

 

              Conductors : In Denmark 1 910 mm2 ACRS (Falcon).

              In Sweden 31 km 1 910 mm2 and 9 km 2 910 mm2 ACRS (Falcon).

 

              Shieldings : Only approx. 3 km out from the converter stations and 17 km on the island of Laesoe are shieled by a single steel wire.

 

              Insulator leakage :

              In Denmark: 2.7 - 3.2 cm/kV (on 250 kV)

              On Laesoe island: 3.8 cm/kV (on 250 kV)

              In Sweden: 2.2 - 2.7 cm/kV (on 250 kV)

 

              Submarine cables :

 

              Denmark : Between main land and the island of Leasoe two oilfilled cables  (flatcable) in parallel connection, each with two Cu -conductors 2 310 mm2. One conductor in cable 1 is connected in parallel with the two conductors in cable 2and used for KS1.

              The total cross-section is 930 mm2.

              The other conductor in cable 1 is connected in parallel with the two conductors in cable 3 and used for KS2.

              Length = 23 km.

              The cables have a single steel armouring of 4 mm.

 

              Sweden : Between Sweden and the island of Laesoe one cable, solid type with oilimpregnated paper insulation and a single Cu-conductor 1 1200 mm2. This new cable was laid in 1991 and replaced the originally 1 625 mm2

              Length = 64 km.

              The cable has a single steel armouring of 6 mm.

              The specification of the new cable is the same as for KS2 cable laid in 1988.

 

HDVC System :

              Konti-Skan 2 :

 

              Route length: Approx. 150 km

 

 

              Overhead lines :

 

              Denmark: The overhead lines are from the design of Konti Skan 1 designed for bipolar operation. Until the addition of Konti-Skan 2 one of the conductors (ACSR = 910 mm2) was used for connection to the electrode station. For the new electrode line, see section Electrodes below.

 

              From 1988 onwards the conductors are used as pole line conductors for KS1 and KS2 respectively. The total length in Denmark is 51 km incl. 17 km on the island of Laesoe.

 

              Sweden: The converter station KS2 at Lindome is situated in the immediate vicinity of the existing Konti-Skan 1 overhead line of which the first 9 km from the coast line (cable landing) to the converter station KS2 at Lindome has been replaced in 1988 by a new overhead line. The conductors for KS 1 and KS 2 are on this section an ACSR 2 910 mm2. Common for the two overhead lines is that they are partly shielded with a single steel wire. The insulator creepage is 3.4 cm/kV (on 285 kV) in both Denmark and Sweden.

 

              Line towers :

 

              Denmark: No changes are made in relation to the original design of KS1.

 

              Sweden: The above mentioned 9 km line is using towers of self-supporting lattice steel structures - common to KS1, KS2 and the electrode line.

 

              On the overhead line from KS1 converter station to KS2 converter station no changes have been made on this part which connect KS1 to the HVDC system.

 

              The two terminals (KS1 and KS2) are situated approx. 30 km from each other.

 

              Submarine cables :

 

              Denmark: Between mainland and the island of Laesoe a third cable has been laid for KS2 in 1988. This is a two conductor (2 500 mm2 Cu) oilfilled flatcable ; it has a length of 23 km and it is connected in parallel with one conductor (310 mm2 Cu) of the old cable 1. The total cross-section is 1310 mm2. The other conductor of cable 1 is connected in parallel with the two conductors (2 310 mm2 ) of cable 2 and used for KS1.

 

              Sweden: Between mainland and the island of Laesoe a solid cable with oilimpregnation has been laid for KS2 in 1988. This cable has a single Cu conductor of 1200 mm2 and it has a length of 64 km. The Danish as well as the Swedish cable have a single steel amouring of 6 mm.

 

 

Electrodes : Common for Konti-Skan 1 and Konti-Skan 2:

 

              Denmark: The electrode station is situated  on the Danish coast. The station is designed as an anode electrode station with 24 graphite electrodes, connected in parallel. Each placed in a wooden structure, where coke backfill is used.

              Resistance = 0.03 total.

             

              The electrode line, consisting of 2 underground cables (2 300 mm2 Al) connected in parallel, laid 1988 when the addition of KS2 was made, between the converter station and the electrode station, a distance of 27 km.

 

              Sweden: While the electrode station on the Swedish coast, which orginaly was designed as a cathode electrode station, should be commmon for KS1 and KS2 in 1988, it was necessary to rebuild it to an electrode station of anode type.That because the current in the cables is desided to flow in either direction depending on mode of operation. The electrode station can operate either as a cathode or as an anode electrode.

              The station is situated approx. 3 km from the Swedish coast and consists of total 30 graphite electrodes on the sea bed at a depth of 7-10m. The electrodes are individually placed in glassfiber sacks with coke backfilling.

              Resistance = 0.1 total.

              The electrode station is connected to the converter station KS2 by approx. 4 km submarine cable, 5 km underground cable and 11 km overhead electrode line. The KS1 converter station is connected with further approx. 30 km overhead electrode line.

 

 

 

 

 

 

DC Filters:   Konti-Skan 1 :

 

              No special DC filters are used.

 

              Konti-Skan 2 :

 

              In order to avoid telephone interference in the vincinity of the HVDC transmission lines a DC filter is installed in both stations. The data for this is :

                   C = 1.2 µF, L = 61.0 mH and R = 1150 .

 

              On the DC side a PLC filter is installed in Sweden only. On the Danish side a PLC filter has been found not necessary because a radio link is designed for the communication of both KS1 and KS2 (KS1 earlier line carrier).

             

 

HVDC valves: 

              Konti-Skan 1 :

 

              Mercury arc valves are used. The valves have water cooled cathodes and air cooled anodes.

              There are 4 anodes/valve, 6 main valves and 1 by-pass valve for each 6-pulse converter unit for 125 kV and 1000 A.

 

              Each terminal has 2 series-connected 6-pulse converter units and 6- and 12-pulse operation is possible.

 

              Konti-Skan 2 :

 

              Thyristor valves are used. The valves are housed indoor and designed as quadruple valves in a suspension structure. The valves are water cooled and air insulated. Each quadruple valve has 4 valve sections (converter arms) each with 48 series connected thyristors which means a total of 192 thyristors for one quadruple valve or 576 thyristors in one 12 pulse converter for 285 kV and 1050 A.

 

Smoothing reactors:

              

              Konti-Skan 1 :

 

              The smoothing reactors are placed on the high voltage side. Oil cooled designed for 266 kV DC and 600mH at 1200 A.

 

 

 

 

 

 

Konti-Skan 2 :

 

The smoothing reactors are placed on the high voltage side.

Air insulated and air cooled through natural convention.

Designed for 285 kV and 160 mH at 1064 A.

 

 

AC Filters:

              Konti-Skan 1 :

 

              Harmonic filters are provided at each terminal :

 

              Denmark :

 

 

Harm.

MVAr

C=µF

L=mH

R=ohm

5

 13.15

  2.08

 195

  6.12

7

  6.65

  1.06

 195

  8.57

11

 11.96

  1.97

  42.5

  2.94

13

  8.85

  1.41

  42.5

  3.48

HP

 40

  6.63

   3.5

 21

 

 

 

              Sweden :

 

 

Harm.

MVAr

C=µF

L=mH

R=ohm

5

 13.15

  2.08

 195

  6.12

7

  6.65

  1.06

 195

  8.57

11

 11.96

  1.97

  42.5

  2.94

13

  8.85

  1.41

  42.5

  3.48

HP

 40

  6.63

   3.5

 21

 

 

              Konti-Skan 2 :

 

              Harmonic filters are provided at each terminal.

 

              Denmark:

 

              Designed as 3 HP filters.

              Furthermore a shuntbank and a shunt reactor are installed.

              The data of filters, shuntbank and reactor are listed in the table below :

 

 

 

 

 

 

N°

one

two

one

one

 

 

 

 

 

Type

  HP 24

  HP 12

  shunt

 reactor

MVAr

  20.1

  55.3

  55.3

  55.4

C = µF

   0.4

   1.1

   1.1

 

L = mH

  43.5

  63.5

 

  9200

R = ohm

  1500

  1250

 

 

Q factor

   4.6

    5

 

 

AC voltage

 400 kV

 400 kV

 400 kV

 400 kV

             

 

              From an operational point of view it was requested to have the possibility of choosing capacitive or inductive compensation.

              Therefore the same circuit breaker is used for the shuntbank and the reactor.

 

              Resulting Impendances, ZPC, for the AC filters and Shunt Banks at Vester Hassing.

 

 

 

 

Operating

Conditions

 

Harmonic

HP12+HP24

HP12+HP24

2xHP12

2xHP12+

 order

+SR

 

+HP24

HP24+SC

No

 

 

 

 

2

1265.0-89.90

1038-89.93

597.2-89.92 

422.7-89.94

 

    

    

  

    

3

 728.4-89.79

 672.0-89.81

385.6-89.79

275.5-89.85

 

    

   

    

    

4

 504.1-89.56

 483.0-89.58

276.0-89.53

199.7-89.66

 

    

    

    

    

5

 373.9-89.12

 364.5-89.14

207.0-89.04

152.5-89.29

 

    

    

    

    

6

 285.6-88.35

 280.9-88.38

158.3-88.20

119.2-88.65

 

    

    

    

    

7

 219.5-87.03

 217.1-87.07

121.2-86.77

 93.7-87.50

 

    

    

    

    

8

 166.6-84.70

 165.4-84.74

 91.2-84.26

 72.9-85.41

 

    

    

    

    

9

 122.4-80.31

 121.8-80.35

 66.1-79.59

 55.0-81.36

 

    

    

    

    

10

  84.8-71.09

  84.5-71.15

 45.0-69.96

 39.2-72.62

 

    

    

    

    

 

 

 

              In case of a fault in one of the converter transformers the shuntbank can be modified for six pulse operation by adding capacitors and reactors for 5th and 7 th harmonic.

 

              However, these components are not installed at present, but the possibilities have been investigated and the control system is provided for this mode of operation.

Sweden:

 

One filter containing 2 double tuned - one HP branch and

2 shuntbanks  with data as tabled below.

 

 No

 one

 one

 one

 two

 

 

 

 

 

Type

11th harm.

13th harm.

 HP 26

 shunt

MVAr

  11.6

  11.6

  23.4

  46.8

C = µF

   2.12

   2.12

   4.27

   8.55

L = mH

  39.5

  28.2

   3.21

   

R = ohm

   1.42

   1.20

  88.7

 

Q factor

  65

  65

   3.1

 

AC voltage

 132 kV

 132 kV

 132 kV

 132 kV

 

 

Resulting Impedances, ZPC, for the AC filters and Capacitors

Shunt Banks at Lindome.

 

 

 

Operating

Conditions

Harmonic

Only

Filter

Filter

 order

filter

+ 1 SC

+ 2 SC

No

 

 

 

2

183.7-90.0

 92.5-90.0

 61.8-90.0

 

     

     

     

3

119.8-89.9

 60.9-89.9

 40.9-90.0

 

     

     

     

4

 86.9-89.8

 44.9-89.9

 30.3-89.9

 

     

     

     

5

 66.3-89.7

 35.1-89.9

 23.9-89.9

 

     

     

     

6

 51.9-89.6

 28.3-89.8

 19.4-89.9

 

     

     

     

7

 40.8-89.4

 23.1-89.7

 16.1-89.8

 

     

     

     

8

31.5-89.1

 18.8-89.5

 13.4-89.6

 

     

     

     

9

 23.1-88.6

 14.8-89.1

 10.9-89.3

 

     

     

     

10

 14.2-87.0

 10.3-87.8

  8.07-88.3

 

     

     

     

 

             

In Sweden the filters also can be modified for six-pulse

operation in case of a converter transformer fault and also

the control system is provided for this possibility.   

 

 

 

 

 

 

 

 

 

References :

              Konti-Skan 1 :

 

              CIGRE 1964 paper 408 : The Konti-Skan HVDC project G. von Geijer, S. Smedsfelt, L.Ahlgren and E. Andersen

              Electra"-1979 n° 63, A.C. harmonic filters and reactive compensation for HVDC". - A general survey by SC14 - WG03.

 

              Konti-Skan 2 :

 

              None at present (1994).

 

 

 

 

 

 

 

 

System correspondent :

 

              Mr Peter Lykkebo Thomsen

              ELSAM - Vester Hassing

              DK-9310 Vodskov

              DENMARK

 

              Telephone : + 45 98 256 199

              Telefax   : + 45 98 257 648 

 

              Mr Ove Lööf

              VATTENFALL AB

              Teknik/TTTT

              S-461 88 Trollhättan

              SWEDEN

 

              Telephone : + 46 520 88000

                              + 46 520 88355 (direct)  

              Telefax   : + 46 520 88775