BY KIM ASBILL PHOTOS BY ROBERT CLARK Investing in resiliency New transmission projects will ensure the reliability of SCE&G s electrical system. 14 INSIGHTS SUMMER 2015
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As you cross over the Ravenel Bridge from Charleston into Mount Pleasant, a long row of strong steel electric transmission structures stands alongside Johnnie Dodds Boulevard, stretching to the I-526 interchange. Thousands of people pass by these structures every day without much thought about them. But in reality, the power carried by this transmission line has a positive effect on the quality of their daily lives. The new transmission line in Mount Pleasant is part of a major effort by SCE&G to enhance the resiliency and reliability of the electric system in its South Carolina service territory. Over the next five years, SCE&G has 39 planned transmission projects each greater than $2 million. Some projects require additional transmission capacity to support system load growth. Other projects are necessary to interconnect the transmission system with V.C. Summer Units 2 and 3, the company s new nuclear plants now under construction. SCE&G s transmission work is always planned with the customer in mind, according to Lee Xanthakos, vice president of electric transmission for SCE&G. Everything we do has a purpose and undergoes a thorough evaluation to prove that the ultimate solution is in the best long-term interest of the customer and the company, he said. SCE&G s Transmission Planning Group plans the electrical transmission system by balancing load forecasts with expectations for customer demand. The demand forecast is developed by the Resource Planning Group. This ensures that the plan for the transmission system is developed on the same basis as the generation system plan, said Clay Young, manager of transmission planning for SCE&G. Young said power generation is forecast to grow at about 1.4 percent per year while demand is expected to grow at about 1.8 percent per year in SCE&G s service territory. One of the main reasons for rebuilding a transmission line is to increase the amount of electrical power that can be transmitted through its conductors, added Jerry Lindler, general manager of electric transmission for SCE&G. SCE&G is required to meet Federal Energy Regulatory Commission (FERC) guidelines for system reliability. Once we make the decision to upgrade a transmission line, it must be built to the current national requirements for clearance and strength of the line, said Cory Touard, manager of transmission siting. Right now, SCE&G is rebuilding a number of existing transmission lines to make room for required new lines in the same right-of-way. This avoids acquiring additional right-of-way from landowners. We often bundle or add additional conductors to existing 115kV lines to expand capacity for growth and reliability, Touard said. The bundling allows for increased capacity at the same voltage. To maintain reliability to meet customer demand, SCE&G s electrical system needs to have resiliency, according to Xanthakos. He defines resiliency as the system s ability to keep going under difficult conditions. In the case of electric transmission, difficult conditions are usually a result of damage to the transmission system from storms, including fallen trees from high winds or ice accumulation, he said. In either case, having some downed power lines is practically inevitable, so the transmission system is built to withstand such a beating and keep going. Young agrees. The North American Electric Reliability Corporation (NERC) discusses resiliency in terms of the ability of the bulk power system to withstand and recover from severe-impact events, 16 INSIGHTS SUMMER 2015
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Young said, adding that those could include weather-related events or a coordinated physical attack, cyber attack or geomagnetic disturbance. Touard explains that outages will still occur, but the investments in resiliency are designed to make recovery times quicker and far less likely in the first place. Resiliency also helps SCE&G maintain reliability while keeping up with demand, even on the hottest South Carolina days when everything is running at full capacity. System Control monitors our service area s power consumption on a real-time basis and sends electronic signals to our power plants directing them to increase or decrease generation based on customer demand, said Xanthakos. For SCE&G customers in coastal communities, the transmission system upgrade has an important added benefit. After Hurricane Hugo in 1989, the National Electrical Safety Code (NESC) increased wind load standards for transmission structures to improve reliability during storms. NESC serves as the authority on safety requirements for power, telephone, cable television and railroad signal systems. To meet NESC requirements, SCE&G is in the process of replacing older, wooden poles with stronger steel poles. The older wooden structures can fail under additional stresses from wind or ice, said Lindler. Whenever a transmission line is rebuilt, we must follow current NESC wind and ice loading requirements. The new steel structures are stronger and can withstand higher wind speeds, even up to 130 miles per hour. This will mean fewer and shorter outages. While underground transmission is discussed as a solution to power outages during storms, Touard said underground lines do not immunize the system from extreme weather events such as hurricanes. Less than one percent of all of SCE&G s transmission lines are underground, and these lines cost significantly more than comparable overhead lines. Underground facilities have support equipment that is above ground, Touard said. This equipment can also be damaged by severe weather. Aside from the cost differential, undergrounding does not solve the reliability issue. Xanthakos added, Reliability is important because modern society relies on electricity for virtually every basic need. We realize that and work hard to minimize the risk of long-term uncontrolled outages. Additionally, I believe our employees want to do a good job and are proud of our service record. Having a reliable system is a testament to their hard work. Hurricane Hugo hit the South Carolina coast in 1989 as a category 4 storm. After Hugo, wind load standards for transmission structures were increased. Older wooden poles are being replaced with stronger steel poles. SUMMER 2015 INSIGHTS 19