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Corrosion caused Longboat power issues during Idalia, FPL says

During Hurricane Idalia, 20 underground transformers failed and left 400 Longboat Key residents without power for 15 hours.

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The results are in from Florida Power & Light's investigation of underground transformers on Longboat Key: Accelerated corrosion within the transformers caused outages during Hurricane Idalia’s storm surge. 

On Jan. 26, West Coast Area Manager of External Affairs Devaney Iglesias with FPL sent Town Manager Howard Tipton a letter updating the town on the results of the investigation that began in September

After the storm, it was estimated that 20 underground transformers had failed, which left about 400 Longboat Key FPL customers without power. Power was restored within 15 hours, according to FPL representatives.

In the letter, Iglesias said several transformers were identified to have “severely corroded hardware” after Hurricane Idalia’s storm surge. This led to the forensic investigation, which was conducted at FPL’s lab, the Reliability Assurance Center.

The report states that the X1 secondary stud on the affected transformers showed significant material loss and, in some cases, was completely corroded. Those transformers had been in service for less than six months.

X1 stud that has corroded away
Courtesy image

It goes on to state that the accelerated corrosion was caused by electrolysis. The transformers were still energized when flooding occurred, and the conditions allowed for an “accelerated galvanic reaction between the copper studs and the stainless-steel components.” 

Iglesias’s letter said FPL will continue working with manufacturers using lessons learned to explore potential improvements in materials and practices.

“While no electrical system is stormproof, FPL is committed to continue improving the resiliency of our grid,” Iglesias said in the letter. “We will use lessons learned from previous storms, including this one, to help reduce the potential for outages associated with future extreme weather events and try to help enhance year-round reliability.” 

Single-phase transformers like this are smaller and simpler than the larger, commercial-use transformers that are currently on back order.
Photo by Carter Weinhofer

A potential mitigation plan for the transformers was also mentioned.

Transformers mounted on 24-inch concrete pads on flooded streets did not experience the same issues, according to the letter. This method of raising the transformers could be a viable way to mitigate future flooding failures. 

Whatever the next steps are, the town is still focused on getting the undergrounding project completed. 

“As discussed with FPL, whatever changes they deem necessary for failing transformers in surge events will not impede the undergrounding project,” Tipton said in an email to commissioners and town staff. “The completion of the undergrounding continues to be the number one priority.” 



Carter Weinhofer

Carter Weinhofer is the Longboat Key news reporter for the Observer. Originally from a small town in Pennsylvania, he moved to St. Petersburg to attend Eckerd College until graduating in 2023. During his entire undergraduate career, he worked at the student newspaper, The Current, holding positions from science reporter to editor-in-chief.

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