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Entergy Mississippi powers life in Winona after tornado destroys substation

Oct 13, 2023

Insights > Entergy Mississippi powers life in Winona after tornado destroys substation


Before power makes it down distribution lines and into homes, a substation is required to transform voltage to a usable level for safe delivery throughout a community. But in Winona, Mississippi, the substation that usually powers the town was destroyed when catastrophic weather swept through the area last week. Luckily, the brilliant technology of a mobile substation will serve Winona while crews rebuild the permanent substation.

On March 24, violent winds spun across Entergy's northern territory, with extensive damage in Winona, Rolling Fork and Silver City, causing power outages for 15,398 customers. An EF-3 tornado passed through the Winona substation on Highway 51, twisting 40-foot steel towers to the ground and causing damage to power transformers, controls, and critical protective equipment. In addition to structural damage inside the substation, the weather event also significantly hit protective equipment, five transmission line structures, and about 40 distribution poles which are used to deliver power to customers. All the destruction combined leaves no through path from transmission to distribution, meaning the substation is off the grid.

"In my 20-year career, this is the first time I’ve seen destruction of this magnitude at a substation," said John Stevens, senior manager, grid at Entergy Mississippi. Stevens predicts it will take months to complete all the necessary repairs and get the station back in usage.

A mobile substation is an innovative and safe solution for emergency power needs. It's able to transfer power from a high transmission level to a lower distribution level, just like a permanent substation. As part of our storm hardening efforts, Entergy Mississippi has four mobile substations ready to deploy when severe weather compromises our substations. Repairing a substation can sometimes be lengthy. So, we use the customized piece of mobile equipment to get power back to customers as quickly and safely as possible.

The equipment is built and delivered on an 18-wheeler style trailer. These units are on average around 80 feet long and 125,000 pounds, requiring crews to lay matting to support the weight while it's on site. It's decked with a power transformer and protection equipment that allows crews to pull in a trailer, make connections, build transmission lines, match voltages to the distribution system and serve customers. These units are not like generators that can just be plugged in to work. It usually takes a day or two to install, but the devastation in Winona has caused the process to take a bit longer.

"It's an engineering masterpiece to see one of these units installed. We must involve support from our engineers, substation support groups, field testers, distribution linemen, transmission linemen and operation center dispatchers, to name a few. It's a huge team effort from an organization perspective and each individual role serves a purpose," Stevens said.

About 50 trained professionals are on site supporting the mobile substation installation, repairing the substation, and clearing damaged equipment. After the twisted steel is removed from the site, it will be sent to a recycling facility. Another 60 to 70 crew members are working outside the station to replace poles and distribution lines that will carry the power to the customer.

Stevens says this storm response is unique because only one or two transformers typically fail in a year, and they typically are not during a storm. This means the teams can isolate the failed device and make the connection to the mobile substation unit quickly. Crews brought a mobile substation to the Openwood station in Vicksburg last year after a power transformer failed and had power restored to the customers in the area in approximately 24 hours. Having this mobile unit installed allowed more time to plan the replacement of the failed device.

A mobile substation allowed Entergy Mississippi to safely restore power to customers in Winona Tuesday night, just a few days after the tornado destroyed the substation. It will continue to support the community while the major restoration process continues.

03/29/2023 Power on wheels