An aging U.S. energy grid is subject to outages — planned and unplanned — due to maintenance, overloads and severe weather.
Additionally, the national substation system is undergoing one of the largest overhauls of the last 100 years as utilities modernize the grid to integrate renewables and other technologies. This means more frequent outages due to upgrade projects.
For support during planned outages, utilities often turn to equipment providers for temporary substation solutions. These allow utilities to reserve their existing fleet for emergent events. Substation solutions can either be fixed or mobile. Mobile substations are self-contained trailer- or skid-mounted units or containers complete with all the elements of a permanent substation, such as power transformers, switchgear, protection and control panels, disconnect switches and diesel generators if needed.
When deciding what temporary substation provider to choose, consider these factors:
Available sizes. United Rentals’ equipment ranges from 5 to 25 mega volt amps, with multiple power ratings ranging up to 138 kilo volt amps and many different delta to wye and wye to delta configurations. Access to a broad range of components enables the company to customize the most effective solution for the situation. "With our strategic partners and engineering capability, we can support multiple different voltages or configurations," said Eric Bateman, regional product development manager with United Rentals.
Flexibility and scalability of the offerings. Flexibility and scalability on the part of a provider may be important depending on one’s needs — for instance, if you need multiple voltage configurations. "Let’s say the utility has five or six different substation voltages in their system," Bateman said. "Rather than spending $3 million on each one of those mobile subs to fleet a backup for everything, United Rentals has the capability to put a voltage regulator on the lower side to allow a multiple tap."
The available tract. Compact tracts require a space-efficient substation. United Rentals can offload the equipment, put it on a pad mount or keep it on trailers, for example, to fit the available space.
Will it need a permit? Heavy haul equipment must be rated for DOT and over-theroad standards and meet weight and dimension restrictions. Some mobile substations will need a special permit. Alternatively, the provider may choose to transport a mobile transformer separately from other equipment.
How is it tested? The components should be tested prior to delivery as well as during commissioning. The provider should loadtest the system with a false load onsite. "Some companies just have the equipment and drop it off," Bateman noted.
Does the company understand isolation and grounding? Safety is a primary consideration. "We make sure our electrical distribution equipment is properly grounded so that in the event of an electrical fault, people are safe," Bateman said. In addition, the temporary system needs to be isolated from the permanent substation. "An independent ground gridding plan that isolates the temporary sub is a safety benefit for the workers, and we take that into consideration. Not every company does," Bateman added.
The provider should also understand arc-flash calculations, potential imbalances and impedances in the line — and high-side and low-side protection, both on the fused or breaker side and on the regulated and nonregulated side.
As utilities struggle to meet the demands of an ever-evolving grid and network, the right temporary equipment provider can be a game changer, especially when it comes to longer-term outage work.
United Rentals specializes in providing customized solutions to boost productivity, streamline scheduling and optimize performance for all sectors of the power industry, whether plant operations, transmission and distribution, substations or renewables. With decades of experience working with some of the largest power providers in North America, its experienced power team stands ready for a planned outage or unforeseen event.
For more information, visit unitedrentals.com.
