A
transmission line is a set of wires, called conductors, that carries electric
power from generating plants to the substations that deliver power to
customers. At a generating plant, electric power is "stepped up"
to several thousand volts by a transformer and delivered to the transmission
line. At numerous substations on the transmission system, transformers
step down the power to a lower voltage and deliver it to distribution
lines. Distribution lines carry power to farms, homes and businesses.
The
type of transmission structures used for any project is determined by
the characteristics of the transmission line's route, including terrain
and existing infrastructure. The diagrams pictured here show typical transmission
towers.
The Super Highway
+/-400 kV DC and 500 kV
The ±400
kV and 500 kV transmission lines are the super highways in the Great River
Energy system. Some 1,000 megawatts of electricity can flow across Great
River Energy’s ±400 kV transmission line that runs 435 miles
from Coal Creek Station, in central North Dakota, to Minnesota. Only electricity
generated at Coal Creek Station and then converted into DC at the plant’s
converter station can flow across the HVDC, or high-voltage direct current,
line. More than 1,600 lattice steel towers carry the HVDC transmission line
across both states. Once in Minnesota, the DC power is converted to back
to alternating current (AC) power and sent along the local transmission
systems for use in Minnesota homes and businesses. Great River Energy also
operates 70 miles of 500 kV transmission lines.
The 345 kV
and 230 kV systems provide the backbone of a transmission system. These
transmission lines are the main connection for reliability purposes between
Great River Energy’s service area and the region’s bulk power
systems. They also provide connections from the DC line and Great River
Energy’s other large generating facilities. By operating transmission
lines at such a high voltage, line losses and voltage drops can be minimized
while the lines deliver large amounts of energy to customers throughout
the system.
The 161 kV
and 115 kV system is the workhorse of the transmission system. It is responsible
for transmitting power from the larger transmission system and generation
facility throughout the entire service territory. 161 kV and 115 kV transmission
lines are the main arteries for electricity, carrying it to and from every
geographical area Great River Energy serves. Some large industrial customers
are served directly from the 115 kV transmission system. Great River Energy
currently operates approximately 30 miles of 161 kV transmission lines and
300 miles of 115 kV transmission lines, connecting more than 60 substations.
Transmission
Nominal Voltage: 161 kV
Type: Single Pole
Typical Tower Height: 70-95 feet
Typical Right-of-Way Width: 100-150 feet
Transmission
Nominal Voltage: 115 kV
Type: Single Pole
Typical Tower Height: 55-80 feet
Typical Right-of-Way Width: 90-130 feet
Secondary Roads 69 kV through 23 kV
The 69 kV
through 23 kV systems transmit power to the distribution substations throughout
the Great River Energy system. These lines also provide connection to some
of the more remote and sparsely populated areas in the Great River Energy
service territory. Many of the smaller rural industrial and larger commercial
customers of Great River Energy’s member cooperatives receive their
power directly from these systems. Great River Energy operates nearly 3,000
miles of 69 kV line or less.
Transmission
Nominal Voltage: 69 kV
Type: Single Pole
Typical Tower Height: 50-70 feet
Typical Right-of-Way Width: 70-100 feet
