For years, during major maintenance outages at its 636-MW Smith Mountain pumped-storage project, American Electric Power (AEP) personnel struggled with poor visibility because of inadequate lighting. To solve the problem, the utility purchased portable light towers powered by generators and installed four 400-watt metal halide area lights on the inside top of the generator domes.
In the past, during maintenance outages, Smith Mountain personnel had to use flashlights, drop lights, or light stands. Extension cords had to be strung, which introduced tripping hazards. The inadequate lighting was especially difficult for the night shift.
Inside the generators, after the rotor was pulled, the utility traditionally mounted six mercury vapor street lights on aluminum pipes on top of the stator windings. The pipes had to be installed for each outage. The amount of labor and time required to set up the street lights was intensive. The lights had to be attached to the pipes and then mounted to existing upright supports. The lights could not be installed until partial disassembly was completed because the lights would be in the way of disassembly. Typically, two mechanics worked on this for one shift. Once the outage work was complete, the lights and the pipes on which the lights were mounted had to be removed.
The utility also brought in six sets of 500-watt quartz halogen tripod lights, purchased from local suppliers. These lights generated lots of heat. This heat, coupled with the lack of air flow and the residual heat from the unit being on line, made working conditions close to unbearable. Additionally, the lights could only be moved as far as the extension cord would reach.
At Smith Mountain, the generators are outside, not in an enclosed building. When personnel worked on the outside of the generators, they utilized existing fixed lighting, along with portable tripod lights. In addition, the plant’s gantry crane is equipped with four stationary metal halide task lights. As long as the crane was over the work area, lighting was greatly improved. However, once the crane was moved, the lighting went with it.
A more suitable solution was needed to improve overall operations.
In 2001, AEP decided to solve this ongoing problem. An upcoming scheduled outage for Unit 3 at Smith Mountain would require extensive night work in order to complete the job in the amount of time being allocated. AEP needed to find a way to do this night work effectively and safely.
An AEP electrical technician came up with the idea of using portable light towers powered by generators or shore power, similar to those used on highway projects, for the outside lighting. The utility purchased three 6-foot by 10-foot trailers from Power Manufacturing Inc., each with a telescoping light tower with two 1,000-watt metal halide lights. Cost was approximately $2,000 each. The masts of the towers are capable of rising to 21 feet. The trailers also have a compartment to add a portable generator. The generators are especially useful in remote locations where power is not readily available and also eliminates the need to use extension cords. When not in use, the trailers are stored in the warehouse at the Smith Mountain facility. These lights greatly aid outdoor night work.
This portable light tower with two 1,000-watt metal halide lights improves visibility for American Electric Power personnel during maintenance outages at the Smith Mountain pumped-storage project. Click here to enlarge image
The solution to providing lighting for the inside work took a little more thought. With a major outage planned for the fall of 2007, the time was right to come up with a cost-effective and labor-saving solution. AEP instrumentation and controls personnel recommended using four 400-watt metal halide area lights because of their long bulb life (15,000 to 20,000 hours) and their high quantity and quality of light. The lights are spaced evenly around the inside top of the dome of the generator air housing. The lights are of a self-contained WalPac design. The lights are plugged into a temporary 100-amp lighting panel using a 30-amp twist lock plug. The lights are installed in such a way that the dome can be removed by simply unplugging the lights. At the end of the outage, the lights are removed and stored for future outages.
When the time came to install the temporary dome lighting at the start of the outage, 1-inch beam clamps, obtained from a local electrical supplier, were used to secure the light fixtures to the inside top of the dome. AEP workers used 1 2/3-gauge service-, oil-, and water-resistant cable extension cords to “daisy chain” the lights together. On the last light, the workers wired in a long power cord with a 20-amp twist lock connector on the end. The twist lock was used to keep the connection secure and to ensure the lights were plugged into the proper receptacle.
To minimize overload on existing receptacles and to shorten extension cord lengths, we built temporary lighting panels with ground fault interrupter (GFI)-protected receptacles. These temporary lighting panels were wired into 60-amp, double-pole breakers in the plant’s existing lighting panels.
The cost of the fixtures was $250 each; supplies for the power cord were approximately $250. All materials were purchased from a local electrical supply house. The installation time required about 12 man-hours.
The results were immediate and positive. Personnel in these work areas were appreciative because of the near daylight conditions, the absence of shadowing, and the lack of heat the lights created in the area. Portable lights are still used to a certain extent because of dark pockets inside the generators. Overall, we have greatly improved our working conditions for minimal cost.
– By Donnie M. Williams, Plant Support Specialist, American Electric Power