Frequency swings caused island-wide power outage

LIHU‘E — All 35,091 members of Kaua‘i Island Utility Cooperative were affected by a power outage late last month, with the first power restorations beginning 18 minutes after the outage occurred.

The outage was due to frequency swings on the power grid, according to KIUC Chief of Operations Brad Rockwell.

Frequency refers to the amount of electricity running through a power grid. Most U.S. grids run on a frequency of 60 cycles per second (60 hertz). Deviations in that pattern can cause problems for electrical equipment assigned to the power grid.

Rockwell explained the April outage happened when the KIUC grid was operating at 100% renewable energy. When that happens, it is slightly more susceptible to problems. The work that KIUC has done over the past few years to enable 100% renewable operation helps KIUC to overcome these problems without any customer impact most of the time.

“For this particular outage, the system began experiencing severe frequency swings, possibly due to renewable generators being out of sync,” Rockwell said.

“Attempts to stabilize were unsuccessful, and the grid eventually went black. Although we are still diagnosing the incident, we’ve already made adjustments that will better alert us should similar conditions occur so we can stabilize and avoid loss of power.”

According to Rockwell, frequency is a unit of measurement that electric utilities use to monitor the stability of systems. Utilities maintain the frequency of their electric system within narrow ranges, and make adjustments to ensure that frequency doesn’t reach a level which can damage equipment. “Frequency swings” refers to movement of frequency within the operating range.

“If system frequency moves to the outer ranges of the acceptable band, our system will disconnect customers and our generators will shut down,” he said.

Rockwell said the protection devices began to operate at 1:38 p.m., and all customers were without power at 1:45 p.m.

“Approximately 50% of customers were restored within 45 minutes, and all members were restored within one hour and nine minutes of the outage occurring,” Rockwell said.

Rockwell noted that the outage was very different from the one in 2019, which was caused by an electrical fault at one of KIUC’s conventional (oil-powered) generators.

“This outage had nothing to do with our conventional generators and, in fact, this equipment was instrumental in restoring power quickly,” Rockwell said.

“Fortunately, KIUC has a robust data infrastructure and access to highly-detailed information about what was occurring on the grid when the outage occurred. This allows us to diagnose what happens and make necessary adjustments so that we can prevent a similar occurrence in the future.”

Rockwell said KIUC’s grid is unlike any other grid in the world because it runs for multiple hours a day at 100% renewable generation. KIUC has operated the grid at 100% renewable for thousands of hours over the past 18 months. The shift to using 100% renewable energy has has resulted in tens of millions of gallons of fuel that are no longer shipped to the island every year. Additionally, that fuel is no longer burned, and the emissions no longer go into the air.

And reliability, according to the statistics, is usually pretty good.

Kaua‘i had the best electric reliability in the state for three of the last five years, with 2020 being the best ever since the entity became a co-op in 2002.

“That being said, there will be issues to be addressed and lessons to be learned along the way,” Rockwell said.

“The fact that our power-generation team was able to bring the grid from completely black to full output in just over an hour is an incredible accomplishment, and a testament to their technical skill, resourcefulness and commitment to our members. While there are inevitable growing pains with shifting to 100% renewable energy, we must recognize the significant benefits it provides for Kaua‘i.”

Some of those growing pains include the fact that the electrical grid has become dominated by inverter-based resources like solar and batteries as opposed to conventional generators, which operate with rotating equipment such as turbines, or KIUC’s generators at Port Allen currently running on diesel.

“Inverter-based resources respond differently to frequency changes than conventional units, and our grid operations are continually adjusting to reflect the different equipment mix supplying the island,” he said.


Stephanie Shinno, education and business reporter, can be reached at 245-0424 or

  1. nobody May 16, 2021 6:47 am Reply

    Feel like you want to go green energy? Just plug in to KIUC. What an amazing team we are lucky to have.

  2. Rev Dr Malama May 16, 2021 7:16 am Reply

    Basically the article suggests that to much power was generated without dumping the excess into batteries or other means of dealing with the infrastructure crisis…. also, no mention of the down powerlines on Hulemalu Rd from tree falls.
    Powering recycling plants and dry methods for sewage processing would be a no brainer for our environment!!!!
    Malama O Moana…. Protect our Ocean!!!!!

  3. randy kansas May 16, 2021 8:55 am Reply

    Just wait until all of our cars are electric and bitcoin becomes main stream, we will not have any electricity at all around here ha ha

  4. Renewable May 16, 2021 10:47 am Reply

    The article states that KIUC has been running on renewable energy for 18 months but prior articles written said that KIUC plans to be operating 100 percent on renewable energy in 2035-2050.

    So what’s going on? Where is the savings from the volatile fossil fuels?

    Why does TGI hide this article on a Sunday when most people don’t read the paper or articles? Oh wait did I just answer my own question?

    KIUC hustles harder than Pete Rose.

  5. Ned May 16, 2021 6:40 pm Reply

    Thank you for the explanation!

  6. Mailman Mike May 17, 2021 10:14 am Reply

    I don’t believe you can power Kauai with 100% renewable energy. No matter how much you charge for electricity. ha ha

  7. Jjjames May 17, 2021 11:46 am Reply

    It’s nice that KIUC “..has a robust data infrastructure and access to highly detailed information about what was occurring on the grid when the outage occurred”. So why does it take 17 days for us “members” of this co-op to find out from a newspaper what happened?

  8. Mailman Mike May 17, 2021 7:47 pm Reply

    Again. I can’t believe this island can operate with 100% renewable energy.

  9. RGLadder37 May 17, 2021 10:36 pm Reply

    The electricity on Kauai required is not continuous 24 hours like Las Vegas, Nevada. They run on nuclear reactors or nuclear fission taking place to generate the electricity for the city. And those 24 hours neon lights throughout the city. On Kauai it needs only residential and hospital to be at 24 hours. Not the business. This island is lucky that they do not use nuclear reactors to generate the electricity. Solar is being considered an acceptable choice.

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