In order to ensure uninterrupted electric service to customers, utility companies must have backup systems. The fastest and most efficient means of accomplishing this is a mobile substation.
When Unitil Energy Systems in New Hampshire needed a new mobile substation it discovered that buying the unit would cost between $1.5 and $2.5 million with up to a two-year delivery. In hopes of reducing costs and time, Skip Zogopoulos, Unitil’s design and standards specialist, suggested the company explore the feasibility of building it themselves. Since these substations are most commonly used in emergencies, its biggest problem would be keeping the total weight under 99,000 lbs. (44,905 kg) so that it could be moved quickly from place to place without the need for special “oversize load” permits.
Unitil’s first step was to determine the weight of the individual components of the substation plus the tractor that would pull it. These were “set” weights. The only remaining place to trim weight was in the flatbed trailer that would carry the equipment.
Rogers Brothers Corporation and E.W. Sleeper, Rogers’s dealer in New Hampshire, worked with Unitil to custom design and build a trailer that would provide the necessary strength and durability within the required weight limits. Aluminum wheels on each of the three axles saved significant weight. Scalloped steel in the trailer frame (holes cut in the I-beams) saved another couple hundred pounds. As a result of these adaptations, the substation’s completed weight was 97,000 lbs. (44,000 kg), well within the limits.
“The trailer and its features are working out better than we expected,” said Skip Zogopoulos. “Our builder, Brad Reed of I.C. Reed & Sons Inc., suggested that the trailer have air ride suspension. The oil-filled equipment in the substation requires us to get the trailer as close to level as possible. The process has turned out to be much easier on this trailer than on our other mobiles without air ride suspension.”
“Even with the custom design on the trailer, we were able to bring the project in at between 50 and 75 percent under the quotes we received. The project was completed in 10 months, saving over a year of time. I commend both Rogers and E.W. Sleeper for doing such a great job and coming in on time and on budget.”
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