Basics of Transmission
Click to enlarge (PDF)
How the Transmission System Works
Electrical lines and facilities are a necessary part of the infrastructure within any community, just like roads, water and sewer facilities.
High-capacity transmission lines operate somewhat like interstate freeways that move large volumes of traffic. Lower-capacity distribution lines operate like streets that crisscross communities and neighborhoods.
When freeways get congested, everything slows down. In a similar way, transmission lines get congested and electricity cannot flow as reliably or economically from the source of generation to your home or business.
The transmission system helps move electricity from the source of generation to your home, farm or business. When electricity is generated it is relayed to a substation, where the voltage is increased and transferred to high-voltage transmission lines (typically 230 or 500 kilovolts).
These lines carry the electricity over long distances to a substation near your home or business. At those substations, the electricity is transferred to lower-voltage distribution lines. Transformers, frequently at the top of power poles, lower the voltage again to 120 to 240 volts before it enters a home.
Ensuring Reliability
More transmission capacity is needed to ensure the continued reliability of the entire electrical grid, which keeps power flowing to all Oregon homes, farms and businesses.
Although Oregon has seen significant growth in population and industry in the last 25 years, no major transmission projects have been built to reinforce the grid. As a result, the transmission system is nearing capacity.
When there is not adequate transmission capacity, lines become congested and reliability problems can occur. Congested lines are essentially clogged, leaving no room for additional electricity to flow to homes and businesses. This can require power generators, such as wind farms, to cut back on the energy they produce because there is not enough room on the lines to transport the electricity.
Reliability problems can occur if there are not enough transmission lines to deliver the power if a line goes down. This can result in power outages throughout the electric system. With the projected increase in Oregon’s population and electricity use, both congestion and reliability must be addressed.
According to a 2008 report by the Idaho National Laboratory: “If the top five planned transmission projects in the Pacific Northwest are not built, the region will lose out on $55 billion to $85 billion in economic activity and up to 60,000 jobs annually over the next 25 years.” The report identified PGE’s Cascade Crossing Transmission Project as one of the top five planned projects.
