HVDC Transmission System

For a high level overview of this and other Manitoba Hydro projects see Hydroelectric Development in Northern Manitoba.

Background
As of 2015, a significant amount of the province’s electricity is produced by five hydroelectric generating stations located on the Nelson River in northern Manitoba. The electricity generated must travel over a long distance to southern Manitoba where most of the electricity demand is located. It is more efficient and economical to transmit electricity over such long distances as Direct Current (DC) than Alternating Current (AC) (see Background on the planning of the HVdc Transmission). A high percentage of the existing generation is connected to two northern converter stations which convert the AC electricity coming from the generating stations to DC electricity for transmission to southern Manitoba. Once there, the DC electricity is converted back to AC electricity. The southern converter station then uses transformers to step down the voltage for distribution to customers.

Location
Bipoles I and II transmission lines follow a 556 mi (895 km) route from the Town of Gillam southward through the Interlake region. Bipole I has its northern terminus at the Radisson Converter Station (CS) near the Town of Gillam. Bipole II extends another 26 mi (42 km) northeast to the Henday Converter Station (CS). The southern terminus of both transmission lines is the Dorsey Converter Station (CS), northwest of the City of Winnipeg.

Components
Components of the existing HVdc transmission system are:


 * Bipoles I and II (±500kV HVdc transmission lines);
 * Radisson Converter Station; and
 * Henday Converter Station.

Bipoles I and II
The HVdc transmission lines are a set of bipolar transmission systems called Bipole I and Bipole II. The term bipole refers to a positive (+) pole and a negative (−) pole on each Bipole transmission line. Each pole is further comprised of two 1.5 inches (4 cm) diameter conductors that are supported by steel transmission towers as shown in Photos 1 and 2.

Bipoles I and II deliver over 70% of the generating capacity from the Nelson River in northern Manitoba to southern Manitoba.





Bipoles I and II Project Data

 * Length of lines:
 * Bipole I: 556 mi (895 km)
 * Bipole II: 582 mil (937 km)
 * Towers:
 * Quantity: 4,103
 * Height: 111 ft (33.8 m) to 155 ft (47.2 m)
 * Average height: 125 ft (38 m)
 * Distance between towers: 1,400 ft (427 m) to 1,600 ft (488 m)
 * Right-of-way: width 449 ft (137 m)
 * Distance between lines I and II: 245 ft (74.7) m
 * Clearing: 41.7 mi2 (108 km2)

Radisson Converter Station
An aerial view of the Radisson CS is shown in Photo 3. The Radisson CS is the northern terminus of Bipole I and is located 1.2 mi (2 km) south of the Kettle Generating Station (GS) and about 460 mi (740 km) north of the City of Winnipeg by air (Map 1). It converts the AC electricity produced at the nearby Kettle GS and Long Spruce GS on the Nelson River to DC electricity for transmission south to the Dorsey CS. The Dorsey CS converts the power back to AC electricity then uses transformers to step down the voltage for distribution to customers.





Radisson Principal Structures
AC switchyard: The electricity produced at the Kettle GS and one-half of that produced at Long Spruce GS enters Radisson CS at its 138 kV switchyard. The switchyard which contains the high voltage breakers, disconnect switches, and AC filters directs the incoming AC power to the converter transformers.

Converter transformer area: The converter transformer changes the AC voltage to the required voltage level for the DC conversion equipment.

Valve halls: At the heart of the converter process are the converter valves, which are located in the valve halls within the converter building which also contains the maintenance shops, the control, mechanical, and electrical rooms.

HVDC switchyard: Electricity converted to DC leaves Radisson CS from the HVDC switchyard and is transmitted south to Dorsey CS. This switchyard contains the necessary switches for isolation or connection of the poles from and to the DC transmission lines.

Henday Converter Station
The Henday CS (Photo 4; Map 2) is the northern terminus for Bipole II. It is located next to the Limestone GS and is 26 mi (42 km) northeast of the Radisson CS.





Henday Principal Structures
AC switchyard: All of the electricity produced at the Limestone GS and one half of that produced at the Long Spruce GS enters Henday CS through its 230 kV switchyard, where the incoming AC electricity is directed to converter transformers.

Converter transformer area: The converter transformer changes the AC voltage to the required voltage level for the DC conversion equipment.

Valve Halls: The actual conversion process takes place in the valve halls. They are located in the converter building, which also contains the maintenance shops, the control, mechanical, and electrical rooms.

HVDC switchyard: Electricity converted from AC to DC at Henday CS is transmitted south to Dorsey CS via the DC transmission line. The switchyard contains the necessary switches to shut off the current if Bipole II is not working, or to switch the current over to Bipole I, if enough room is available to carry the current.

Radisson Converter Station
Main access to the region during construction was by the Hudson Bay Railway line (now HBR; Canadian Pacific Railway (CNR) at the time) which had a rail station and siding at the Town of Gillam. A 0.6 mi (1 km) rail spur was added near the Kettle GS site to the Radisson CS site as part of construction. A new 4.4 mi (7 km) permanent gravel road was built from the Town of Gillam to the Kettle GS site and the Radisson CS site to link these projects to the community. The Town of Gillam was not connected to the provincial road network until after completion of the projects. The community has had a permanent airstrip since 1967, which was used as required during construction.

Henday Converter Station
Access to the site was by a 14 mi (23 km) extension of the permanent gravel access road at the Long Spruce GS and a 1.5 mi (2.5 km) rail spur from the Hudson Bay Railway line (now HBR; CNR at the time) to the Henday site. The access road was not connected to the provincial road network until just after completion of the converter station.

Bipole I
Construction on Bipole I started in 1968 and was completed in 1971. Routing of the line included large tracks of muskeg country, providing difficulties for construction. For economic reasons, construction of the line had to be undertaken during winter months when the ground was frozen to allow for the passage of heavy equipment.

Radisson Converter Station
Construction on the Radisson CS began in 1967 and was completed in 1977. The converter station was not ready when the first units at the Kettle GS were commissioned in the fall of 1970 so the DC line was used to transmit AC power to the south until early 1971 when the Radisson CS began operation. After 1978 the Radisson CS began converting power for half of the Long Spruce GS.

Bipole II
The Bipole II transmission line was previously constructed along with the Bipole I transmission line as far north as the Radisson CS. Construction of the 26 mi (42 km) extension of the Bipole II transmission line to the new Henday CS started in 1977. The first stage of Bipole II was complete in 1978 and the second stage was completed in 1985. In 1992 a 6 mi (9 km) Bipole II back-up loop originating at the Henday CS was constructed.

Henday Converter Station
Construction started in 1970. It began transforming power from the Long Spruce GS in 1978 and from the Limestone GS in 1990.

Bipole I & II
Various temporary mobile construction camps and access trails on or adjacent to the transmission line right-of-ways were used for the construction of Bipoles I and II.

Radisson Convertor Station
The temporary construction camp for the Kettle GS was used for the Radisson CS. Work areas were established near the Radisson CS site. The workforce commuted from the Kettle GS camp to the Radisson CS site on a daily basis and lived there for several weeks at a time and travelled to their homes during their days off. A 79 mi (127 km) 138 kV transmission line was built from the Kelsey GS to the Radisson CS site to provide construction power for both the Radisson CS and the Kettle GS. To achieve this, short tie-ins from the line provided electrical power to the Kettle GS construction site and nearby Town of Gillam, which was about to undergo a major expansion.

Henday Convertor Station
No on site construction camp was created as the workforce commuted from the Long Spruce GS construction camp. A 21.5 mi (34.6 km) extension of the 138 kV transmission line (KN36) called the Kettle Station Tap to the Limestone GS was built from the Kettle GS to the Henday Construction power station to provide construction power for both the Henday CS and ultimately for the Limestone GS.

Operations
Access: The Provincial Road (PR) 280 to the Long Spruce area was constructed at the end of construction of the Long Spruce GS. It connected with the existing permanent roads used for construction of the Kettle GS, the Long Spruce GS, the Radisson CS and the Henday CS to become part of the provincial road network as seen today. PR 280 now goes to the Town of Gillam and the segment from the Long Spruce GS turnoff to the Limestone GS/Henday CS area is now designated as PR 290.

Communication System: An essential component of the HVdc transmission line system is a complex high-performance communications system that is used to protect and control the HVdc Transmission System. Prior to 2004, the communication system consisted of two microwave systems each linking the Radisson and Henday converter stations in the north to the Dorsey CS in southern Manitoba. This dual route microwave system was operated to protect and control the HVdc Transmission System and other facilities in the north, such as the Grand Rapids, Jenpeg, and Kelsey generating stations.

One of the microwave systems follows a route through Manitoba’s Interlake corridor while the other was located on the east side of Lake Winnipeg. In October 2004, Manitoba Hydro replaced the east of Lake Winnipeg microwave system with a new fibre optic cable system installed in the Interlake corridor. This new fibre optic cable works alongside the remaining Interlake digital microwave system, providing enhanced reliable communications for all major substations and generating stations along the 653 mi (1,050 km) route as well as facilitating voice and data communications at district offices and other Manitoba Hydro facilities.

Rehabilitation
Radisson Converter Station: The former construction waste disposal ground was investigated in early 2001, with a subsurface drilling investigation (Phase II Environmental Site Assessment) conducted later in 2001 and into 2002. Groundwater monitoring and sampling has been conducted on an annual basis since 2002.