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THE PACIFIC INTERTIE SCHEME

 

 

 

Between:      Celilo, The Dalles, Oregon and Sylmar, California

 

 

Operated by:  Celilo : Bonneville Power Administration, Portland

              Sylmar : Los Angeles Department of Water & Power

 

 

Manufacturer:

              ASEA, Sweden, and General Electric

 

 

Commissioned:May 1970, upgrade 1985 (by adding a thyristor bridge in serie).

              Expansion 1989 (by adding parallel converters).

 

 

Main Purpose:

 

              The generation resources of the Northwest are made available to the Southwest during peak load periods. In return, the Northwest is provided with energy during off peak period (Capacity-Energy Exchange).

              The transmission of surplus hydro power from Northwest when available.

 

 

MAIN DATA :  

              Bipole : 2000 MW at ± 500 kV and 3100 A/pole.

 

              Monopolar : 1550 MW with earth return or 1000 MW with metallic return.

 

 

AC NETWORKS :

              At both terminals, three single phase converter transformers are used for each of the four 6-pulse converter groups/pole, and three single phase-3 winding converter transformers are used for the expansion converters (1 & 2).

 

 

 

 

 

 

              Celilo Converters 3 & 4 :

                                                     + 13%

              6 banks-289 MVA, 3 phase, 235    /113.3 kVLL

                                                     - 2%

             

 

                                             + 15%

              2 banks-268 MVA, 3 phase, 235      /85.kVLL

                                                      -  2%

 

              Celilo Converters 1 & 2 :

                                           + 22.5%

              2 banks-639 MVA, 3 phase,525     /205.3 kVLL

                                           -  5%

 

              The pre-expansion project transformers are connected to the 230 kV A. C. system. The expansion transformers are connected to the 500 kV A.C. system. Celilo short circuit capacity : Minimum 17.000 MVA. Normal ESCR without filters is 6.7. Minimum ESCR without filters is 5.5.

 

              The transformers are connected to the 230 kV

              A.C. System.

              Short circuit capacity : min. 6750 MVA

 

 

              Sylmar Converters 3 & 4 :

 

                                                     + 15%

              6 banks-289 MVA, 3 phase 235      /113 kVLL

                                                     -  4%

 

                                            + 15%

              2 banks-268 MVA, 3 phase, 235     /85.5 kVLL

                                           -   4%

 

              The transformers are connected to the 230 kV

              A.C. system. Short circuit capacity :

              min 10.000 MVA

 

 

CELILO

AC

FILTERS

(single

Tuned)

Harm.

MVAr

C = F

L = mH

R =

5

   51.3

  2.469

 114

   0.86

7

   25.7

  1.260

 114

   1.18

11

   26.6

  1.322

  44

   0.72

13

   19.0

  0.946

  44

   0.86

HP 18

   77.8

  3.9

   5.5

  40

HP 27

  116.7

   5.85

   1.67

  56.7

 

 

 

CELILO

AC

FILTERS

(double

Tuned)

 

Harm.

MVAr

CHV =F

CLV =F

LHV =mH

LLV=mH

13/24

140

1.34

   3.34

  16.98

6.81

36/48

115

1.11

  13.27

   3.68

0.31

 

 

 

HVDC-system :

              Route length = 1361 km

 

              Overhead lines :

 

              Conductors : 2 X 1171 mm2 ACSR/pole.

             

              Note : Conductor cross-sectional area does not include steel reinforced core.

 

              Line towers : Self-supporting and guyed towers are used. All self-supporting towers are steel structures. Guyed towers for the Southern section are steel and for the northern section aluminium.

 

              Shieldings : The northern section has a single steel shielding wire of 127 mm2. The southern section has 2-steel shielding wires each of 97 mm2.

 

              Insulator leakage : varies from 1.8 to 2.6 cm/kV (for 500 kV)

 

             

Electrodes  :

              At Celilo : the ground electrode is located 10.6 km from the converter station, in Rice Flates. The electrode is designed as a ring type 3255 m circumference, 1067 cast iron anodes, and 2' X 2' coke backfill is used. Total resistance in 2 parallel electrodelines and ground electrode = 0.43 ohms.

 

              At Sylmar : the sea electrode is located 48 km from the converter station, in the Pacific Ocean and consists of a linear array of 24 horizontal electrode elements made up of silicon-iron alloy rods suspended 0.5 to 1 m above the ocean bottom and located within concrete enclosures. Total resistance in 2 parallel electrode lines and sea electrode = 1.13 ohms.

 

 

 

 

 

              Electrode lines :

 

              At Celilo : 2 X 644 mm2 ACSR  conductors in parallel supported by the D.C. line towers.

 

              At Sylmar : 2 X 644 mm2 ACSR conductors in parallel are used for the first 35 km, supported by the 230 kV line towers. For the remaining 13 km, two parallel paper-insulated underground cables are used, each with a 633 mm2 Cu-conductor.

 

 

 

DC Filters  :

Each pole has one double-tuned HP and 6th harmonic filter and one single-tuned filter tuned to the 12 th harmonic. The expansion project added one 12/24 harmonic filter and one 2/12 harmonic filter. The filters are connected between the pole and the electrode lines.

 

 

CELILO

AND

SYLMAR

D.C.

FILTERS

Harm.

CHV= F

CLV= F

LHV= mH

LLV= mH

12

  0.39

 

 125.3

 

6/HP

  3.52

  15.01

 

  10.55

2/12

  1.1

   0.34

 225.87

 741.2

12/24

  0.4

   0.8

  61.08

  30.54

 

 

 

 

HVDC-Valves :

              Mercury arc valves are used for 6 of the converter groups. In 1984 two additional solid state thyristor groups were added at the highest kV-BIL level. The valves have air-cooled anodes and a water-cooled cathode.

 

              There are 6 anodes/valves. The thyristor groups are water cooled valves. Six valves and one bypass-valve form a 6-pulse mercury-arc converter group for 133 kV ; the thyristor groups operate at 100 kV .

 

              Each pole has 4 series connected 6-pulse converter groups. The smoothing reactors rated at 2000 A are placed on the high voltage side, designed at 0.4 H to 0.6 H at 400 kV D.C. and 10 mH at 500 kV D.C.

 

 

 

 

              In 1989 expansion project converters were added in parallel with the mercury arc converters in each pole. The expansion converters are 12 pulse converters capable of operation at 367, 400 and 500 kV in order to match the voltage levels of 3 or 4 group mercury arc converter operation in parallel. The expansion converter valves are water cooled. The valves are arranged in a quadruple valve arrangement. Each valve branch includes 4 series connected modular units, and each modular unit consists of 30 thyristor levels. The expansion smoothing reactors are placed on the high voltage side and are rated at 0.5 H, 1100 A.

 

References :

 

 

System correspondent :

 

              Mr Richard BUNCH

              Bonneville Power Administration

              P.O. BOX 3621

              PORTLAND

              OREGON 97208

              USA

 

              Telex :

              Telephone : + 1 206 690-2342

              Telefax :   + 1 206 690-2963