Click on title to view scheme

 

THE FENNO - SKAN SCHEME

 

 

 

 

Between :     Finland (Rauma) and Sweden (Dannebo)

 

Power Co :    Imatran Voima Oy, Helsinki

              Svenska Kraftnät, Stockholm

 

Manufacturer :

              ABB Power Systems for the converter stations,

              ABB Cables and Alcatel STK for the sea cable.

 

Comissioned : 20 th of November 1989

 

Main purpose :

*   Peak power reserve for both countries

*   Transit power from northern Sweden to southern Sweden via the Finnish network

*   Emergency power supply

*   Increased power transmission capacity on the AC interconnections due to higher stability limits.

 

Main data :  

              Monopolar 500 MW at ± 400 kV DC and 1280 A.

              Sea return with anode on the Swedish side.

 

AC Networks :

 

              The converter stations are connected to the 400 kV AC system on each side. Double-breaker bays feed the HVDC link. On the Swedish side the breakers are located 2 km away from the converter at the Forsmark nuclear power station.

 

              There are three 1-phase 3 winding converter transformers at each terminal :   

             

                AC  Side      Valve  side       Valve  side

                                        Y                 D

 

Rated power MVA    194.6            97.3          97.3

Rated voltage kV   405 : 3        161.4 : 3    161.4

 

 

Tapping range      + 18

                           x 1.25

                     - 7

 

 

 

 

                        6000-240

                 ESCR : = 11,5  (norm. SCR level)

                          500

 

 

                        4400-240

                       =  8,3  ( min. SCR level)

                          500

 

 

HVDC SYSTEM :

              *      Route length = 233 km,

              *      Sea cable = 200 km.

 

              There is no overhead pole line  on the Swedish side.

              Overhead line  on the  Finnish side = 33 km.

 

              Line towers :       Self-supporting steel

                                  towers.

 

              Conductors :        Six 565/72 ACSR are used

                                  as pole conductors.

 

Submarine cable :

              Solid type with oilimpregnated paper

              insulation and a single Cu - conductor = 1200 mm2 and double cross armouring.

 

Electrodes :  The anode on the Swedish side consists of forty 20 m2 nets of titanium laid on the sea bed.

              R = 0,2 ohms ; The cathode on the Finnish side consists of a 1500 m x 700 m loop of 300 mm2 copper wire ; R = 0,11 ohms.

 

              A 29 km long overhead electrode line is built on the Swedish side. Four 774 mm2 Al conductors are used

 

              On the Finnish side four 565/72 ACSR conductors are used. They are insulated from the pole tower and equipped with spark gaps and will therefore serve as earth wires as well.

 

 

 

AC filters :

              Harmonic filters are provided at each terminal:

 

 

 

 

 

              Finland : Two double-tuned filters (80 MVAr each)

 

Harm.

MVAr

C=µF

L=mH

R=ohm

 

 

  0.79

 89.69

 

11/13

40

 28.24

  2.51

   0.16

 

 

  0.80

 14.10

 667

24/36

40

  4.77

  2.46

 176

    

 

              Furthermore one shunt capacitor bank = 80 MVAr.

 

 

              Sweden : One double tuned filter

 

Harm.

MVAr

C=µF

L=mH

R=ohm

 

 

   0.73

  97.90

  

11/13

37 

  26.00

   2.70

   0.29

 

 

 

 

 

HP

43

   0.85

  20.80

 391

 

 

              Furthermore one shunt capacitor bank = 160 MVAr.

 

 

DC - filters :

              On the Finnish side one filter with two branches

              one double-tuned to the 12 th and 24 th harmonics and the other a high pass branch.

 

 

Harm.

MVAr

C=µF

L=mH

R=ohm

 

 

 

 35.90

 

12/24

 

  0.94

 18.66

 

 

 

 

 

 

HP

 

  0.94

  7.32

  940

 

 

 

              On the Swedish side there is a 36 µF low voltage filter between the neutral bus and ground.

 

 

HVDC valves :

 

              The thyristor valve structures are suspended from the ceiling. Each of the three   structures contains four valve functions thereby forming a 12-pulse converter.  Each valve function is built up by 66 series connected thyristors.

 

 

 

 

Valve cooling :

 

              The valves are cooled by deionisized water circulated in a closed loop system. The heat is transferred to a secondary circuit which is cooled in outdoor coolers.

 

Smoothing reactors :

               

              On the Finnish side there are two reactors in series, 225 mH and 112.5 mH. On the Swedish side there is only one of 112.5 mH. All reactors are of dry type air cooled and air insulated.

 

References :

 

1             Embaie, Holmberg, Jonsson, Auranne, Hagman, Jääskeläinen, 1988, "Fenno-Skan HVDC Link as a Part of Interconnected AC/DC System"

              CIGRE Report 14-2

 

2             Carlsson L., "Fenno-Skan undersea HVDC link carries 500 MW over 200 km" Modern Power Systems, January 1990

 

3             Nyman, Jääskeläinen, Vaitomaa, Jansson, Danielsson, 1991, "The Fenno-Skan HVDC Link Commissioning"

              IEEE PES Winter Meeting

 

4             Pottonen, Hirvonen, Jääskeläinen,  Vaitomaa, 1991, "The Network Interaction Tests of the Fenno-Skan HVDC Link and the Comparison of the Results with the Simulations"

              IEE Fifth International Conference on AC and DC Power Transmission

 

 

System correspondent :

 

              Pehr-Olof LINDH

              Finnish Power Grid Plc

              P.O. Box 530

              FIN-00101 Helsinki

              Finland

             

              Telephone :  +  358 30 395 5138

              Telefax   :  +  358 30 395 5201

 


 

 

 Code

Redundancy

 Reserv System

 

 Spare parts

 

FENNO

 

Yes/No

 Yes/No

Min. time needed

Yes/No

Min. time needed

 

 

 

 

 for change 

 

to install spares

 

 

1)

2)

over (hours)

3)

(hours)

 

 

 

 

 

 

 

  AC Filter and Shunt  Bank

 AC-E.F

   No

   No

 

   Yes

   6-24 hrs. 

  AC Switchyard Equipment

 AC-E.SW

   Yes

 

 

   Yes

       6 hrs.

  AC Control and Protection

 AC-E.CP

   Yes

 

 

   Yes

       3 hrs.

  Converter Transformer

 AC-E.TX

   No

   No

 

   Yes

   6-24 hrs.

  Synchronous Compensator

 AC-E.SC

   -

 

 

 

 

  AC and Auxilliary Equipment

 AC-E.AX

   Yes

 

 

   Yes

       6 hrs.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

  Valve Electrical

 V.E

   No

   No

 

   Yes

       4 hrs.

  Valve Cooling (integral with valve)

 V.VC

   Yes

 

 

   Yes

       4 hrs.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

  Local HVDC Control and Protection

 C-P.L

   Yes

 

 

 Yes

       3 hrs.

  Master HVDC Control and Protection

 C-P.M

   Yes

 

 

 Yes

       3 hrs.

  Telecommunication

 C-P.T

   Yes

 

 

 Yes

   3-12 hrs.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

  DC Filters

 DC-E.F

   No

   No

 

   Yes

   6-24 hrs.

  DC Switching Equipment

 DC-E.SW

   No

   No

 

   Yes

       6 hrs.

  DC Ground Electrode

 DC-E.GE

   No

   No

 

   No

 

  DC Ground Electrode line

 DC-E.EL

   Yes

 

 

   Yes

      10 hrs.

  Other DC Yard and Valve Hall Equipment

 DC-E.O

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

  DC Transmission Line

 TL

   No

   No

 

   Yes

 10-600 hrs.

1)  2) 3) please give more detailed information on table 2


 

*  THE FENNO SKAN SCHEME  *

 

 

 

1 * REDUNDANCY

 C-P.L. - The pole control cubicles are not doubled,
 C-P.M    all others are.

 C-P.T  - The equipment is doubled except for the

          antennas.
 DC-E.EL  The conductors are doubled, the towers not

 TL       The conductors on the overhead line are doubled,
          the towers not.

          There is only one DC submarine cable.


 2 * RESERV SYSTEM














 

 3 * SPARE PARTS

 AC-E.F  - Some spares are stored in Sweden some in
           Finland.
 AC-E.TX   Min. time to repair depends on what part is
 DC-E.F    needed.

 AC-E.TX - A spare transformer unit do not exist so a
           major failure means a one year outage.

 TL      - Min. time to repair : Overhead line 10 hours
                                 Submarine cable 600 hours.