SwePol

SwePol is a 254.05-kilometre (157.86 mi)-long monopolar high-voltage direct current (HVDC) submarine cable between the Stärnö peninsula near Karlshamn, Sweden, and Bruskowo Wielkie, near Słupsk, Poland.

SwePol is a high voltage cable with a cross section of 2,100 square millimetres (3.3 sq in). It runs for 222 kilometres (138 mi) as underground cable from Stärno HVDC Station to the shore of the Baltic Sea. The 239.28 kilometres (148.68 mi) long submarine cable comes ashore in Poland near Ustka at 54°34′25″N 16°46′57″E and runs underground for the remaining 12.55 kilometres (7.80 mi) to Bruskowo Wielkie HVDC Static Inverter Plant.

Unlike other monopolar HVDC schemes, Swepol uses a metallic return consisting of 2 cables with 630 square millimetres (0.98 sq in) sections for the submarine portion of the line, and a single cable with 1,100 square millimetres (1.7 sq in) sections for the land portions.

Both stations use air-core inductance smoothing rectifiers of 225 mH and a weight of 27.5 tonnes, with filters for the 11th, 13th, 24th, and 36th harmonics. Each filter consists of a coil and a capacitor switched in row. The filters for the 11th and 13th harmonics are adjustable. The filters deliver a reactive power of 95 Mvar. Additional 95 Mvar reactive power is delivered by a capacitor bank. Each station's static inverter, which is switched as a 12-pulse thyristor bridge, consists of 792 thyristors arranged in three 16 metres (52 ft) high towers installed in a valve hall.

The SwePol link was inaugurated in 2000 and can transmit up to 600 MW power at a voltage of 450 kV. It is owned and maintained by SwePol Link AB, a company jointly owned by the state-owned Swedish power company Svenska Kraftnät (51%), Vattenfall (16%), and Polish transmission system operator PSE-Operator (33%).

Since coming online, 11 instances of cable damage have occurred: one on the high voltage line and 10 on the return cable. Causes have included ship anchors, fishing nets, fire, and grid power disturbances. On February 14, 2005, the smoothing reactor at the HVDC station at Bruskowo Wielkie was destroyed by fire. Repairs took 20 hours.