PMG Transmission Line Q & A

What is being proposed? The proposed project will include converting the existing 69-kV transmission lines connecting the Hennepin, Arbor Lake, Cedar Island, Bass Lake and Plymouth substations to 115-kV transmission lines. New 115-kV transmission lines would be extended to the major transmission substations at Elm Creek and Parkers Lake.

The total proposed project would involve about 14 miles of transmission line -- two-thirds of which would follow existing transmission line corridors and use existing rights-of-way. This recommendation would provide long-term reliable service, enabling continued growth in the area for the next 30 years.

Convert approximately 2.25 miles of existing Xcel Energy 115-kV line to 115-kV double-circuit line from the Elm Creek Substation to the 69-kV line located near Zachary Lane. This portion of the project would utilize an existing Xcel Energy 115-kV transmission line.
Rebuild 0.5 mile of 69-kV line to 115-kV line to the Hennepin Substation, using the existing 69-kV transmission corridor.
Convert and rebuild approximately 7 miles of existing 69-kV line to 115-kV line from the end of the Elm Creek double-circuit line to the Plymouth Substation, using the existing 69-kV line corridor.
Build approximately 4.25 miles of new 115-kV line from the Plymouth Substation to the Parkers Lake Substation along the I-494 corridor.

How long will the solution last? This recommendation would provide long-term reliable service, enabling continued growth in the area for the next 30 years.

What will happen if nothing is done? By 2004, the system will not be compliant with NERC rules that require the system be capable of carrying 100 percent of the electric load when one line is out of service. The North American Electric Reliability Council (NERC) is a voluntary organization that promotes bulk electric system reliability and security. As a result, some of the area's electric load would have to be shed, or turned off, during the hottest summer days in the event a nearby transmission system failed.

What type of transmission structures will be used? The transmission structures used for this project will be determined by the characteristics of the final route, including terrain and existing infrastructure. The appearance of individual structures will vary with the final route and design but in general the structures will be a single wood pole with horizontal insulators. Some locations may require larger steel poles.

How tall will the poles be? The height will be vary with the final design once the route is determined but in general the structures will be 15 to 20 feet taller than the existing poles.

Will the total number of lines on each pole change? No. Presently, there are one or two lines with several wires depending on location of the pole. The transmission line consists of the four top wires (3 phase and 1 shield wire). The distribution line, which consists of four wires (3 phase and 1 neutral), is underneath the transmission line. In some cases, telephone or cable TV lines are below the distribution line on the pole.

Will the poles go in the same place? The location of poles will be determined during the detailed design phase of the project. Pole location may change because the typical space between poles on a 115kV line is greater than on a 69kV line. There may be some ability to shift poles slightly (about 10 feet) before construction.

Were other options reviewed? Great River Energy reviewed possible options, including upgrading the existing 69-kV transmission system. This alternative would have to be completed very soon and would only provide a relatively short-term solution for the area's growing energy needs. An upgraded 69-kV transmission system would still require the use of larger poles and wires, similar to the ones that would be used for a 115-kV transmission project.

What is the downside of the proposed alternative? The existing structures need to be removed and replaced with new poles. This will require some construction in people's yards. Other options could also require replacing poles and wires.

Will my yard be damaged during construction? Although we try to keep construction damage to a minimum, some may occur. Any damage will be repaired.

Will the new line follow the same route? The route for the new line will be determined by the Minnesota Environmental Quality Board (EQB). The preferred route would follow the existing line. Some new sections of route will be required on the north end along Hwy. 610 and also south of Schmidt Lake Road.

How was the corridor selected? The corridor is defined by the two end points, the Parkers Lake and Elm Creek substations, and four distribution substations, Plymouth, Bass Lake, Cedar Island and Arbor Lakes. The line must connect to each of these locations. Possible routes between each of these are identified. The corridor, as determined by state rules, is 1.25 mile wide.

When acquiring new easements are the old ones vacated? Yes. New easements are obtained if the old easements are not adequate. Then the old easement would be released.

Will the line be noisier? Slightly but it will not be noticeable. The crackling or hissing noise around a line is caused by corona. Corona occurs when the voltage of the line exceeds the insulating capability of air. Corona is higher on misty days because the air has a lower insulating ability when wet.

Will the new line cause radio or television interference? Radio or TV interference is a function of the signal strength and transmission line induced noise. Noise with respect to interference is typically caused by loose hardware on the pole. This is easily corrected by tightening the loose part.

Why can't you use the towers along 494? Those towers are owned by Xcel Energy and were designed specifically for the wires currently on them. They are not strong enough to support additional wires, or conductors. We would still need to get the line to the existing substations, which would be very difficult. Currently there are three 69 kV transmission sources serving the area.

Why are two 115 kV sources better than three 69 kV sources? The new 115 kV line would connect directly to the 345 kV transmission system at Elm Creek and Parkers Lake. The 345kV system connects directly to generating plants and is the most reliable system in this area. This direct connection results in a shorter path between source and load, therefore a lower probability of problems. The existing 69kV system is supplied by a combination of 69kV and 115kV sources. Higher voltage lines also have design characteristics that are better able to withstand lightning strikes, ice or other weather disturbances. In general, the higher the voltage the more reliable the system.

How old are the substations the new line will connect to? Elm Creek was built in the mid-1990s, Parkers Lake about 1970. Substations have an almost infinite life span; equipment is replaced if it no longer operates as needed.

Will the substation in my neighborhood change? The substation footprint will stay the same although some equipment inside the fence will be changed. I live at a corner where the lines go west, south and east.

What will happen at that location (Bass Lake Tap location)? If the route of the new transmission line follows the existing 69 kV corridor, then the switch and line to the west will be retired and the lines to the east and south will be rebuilt.

What about conservation? Wright-Hennepin Electric has successfully implemented conservation and load management programs that have helped postpone the need for this transmission project. Cycled air-conditioner and interruptible water heater programs are two examples of successful programs that have trimmed electric demand in the area. Although the number of customers enrolled in these programs continues to grow, the number of new electric customers in the area will outpace the programs' impact resulting in electric demand that causes the need for this project.

Could distributed generation handle the area's growth? Distributed generation is the small-scale production of power at or near the site where power is used, thereby limiting a customer¹s reliance on the bulk power grid. Distributed generation can be a very important component of a utility's electric power portfolio. However, the growth in the Plymouth-Maple Grove area is so significant that distributed generation is not a reasonable long-term solution or viable replacement for an upgraded transmission line in meeting future electricity needs.

Who will benefit from the transmission improvements? A 115 kV transmission system would improve the area's electric reliability benefiting customers of Wright-Hennepin Electric. In addition, the project will improve the reliability for many area Xcel Energy customers.

When will the line be built? Great River Energy has started the permitting process, which consists of filing a certificate of need with the Minnesota Public Utilities Commission and applying for environmental and routing permits from the Minnesota Environmental Quality Board. Routing and land acquisition will follow. The project is tentatively scheduled for completion by late 2006.

Will the new line be safe? Every effort is made to ensure safety in construction, operation and maintenance of transmission lines. Great River Energy's practices meet or exceed standards set by recognized electric national safety codes and safety codes adopted by local governing units. Lines and line structures are designed to withstand extreme weather conditions. Protective devices at the source of the lines stop the flow of electricity under abnormal operating conditions.

What about EMF? Electric and magnetic fields (EMF) are created by any wire conducting electricity, including transmission lines, household appliances and business equipment. These fields are strongest close to the source (wires) and rapidly diminish as you move away from the source. EMF levels from transmission lines diminish rapidly with distance.

EMF is a function of the amount of current or amps that flow on the line, and therefore EMF varies hour to hour. With the same circumstances the EMF levels from the new 115 kV line will be about two-thirds that of the existing 69 kV line.

For more information about EMF, contact the Environmental Health Division, Minnesota Dept. of Health at 651-215-0699 or visit their EMF website. The National Institute of Environmental Health Sciences provides another helpful website.

List of additional EMF resources

Why not build the transmission line underground? Constructing long-distance, high-voltage transmission lines underground is feasible but not practical because of electrical losses, reliability and cost factors. Locating and repairing line failures also takes longer on underground systems. The reactive losses of the cable are substantially higher than overhead lines. Installation requires lengthy disruptive construction techniques. Design concerns such as ampacity and heat dissipation are frequent limitations. Underground systems are justified primarily in heavily populated downtown urban centers, where right-of-way is severely limited for overhead lines.

Can I view a copy of the presentation from Great River Energy's December 3 open house? Yes, click on this link to view a PDF file of the presentation.