Unexpected high-voltage electric discharge at Kihei substation triggers malfunction of transmission lines, causing widespread blackout.While some may have hoped that the power outage on Wednesday, April 2, was just a postponed April Fool’s Day prank, they soon discovered it was the real thing. Shortly after 1 p.m. on Wednesday afternoon, thousands of light bulbs, computer screens and coffee makers across Maui shut down for several hours. But as the power drained from the transmission lines carrying electricity to 30,000 households in South Maui, Upcountry, East Maui and parts of Central Maui, West Maui was unaffected by the blackout.
Power was restored to most areas by 5 p.m. that day, but some Upcountry residents were left in the dark until 8 p.m. While power to some areas was restored within two hours, some Central Maui and Upcountry residents waited much longer. Areas deemed as “critical infrastructure,” including Maui Memorial Medical Center, Kahului Airport and the Maui Police Department, were first on the list to regain power. But as the hours passed by, some local businesses, including Cold Stone Creamery in Kihei and Ono Gelato in Pa‘ia, were anxious to have power restored—as storeowners kept a wary eye on the inventory.
Maui Electric Company (MECO) officials quickly traced the origin of the blackout to its substation in Kihei, but the specific cause of the outage was not announced until Thursday.
According to MECO spokeswoman Kau‘i Awai-Dickson, the cause of the blackout was a “flashover” that originated at the Kihei substation. The flashover, or unexpected high-voltage electric discharge, triggered the 69,000-volt transmission lines to malfunction, causing two of the four generator units at the main power plant in Kahului to shut down. The Kahului power plant generates 37.6 megawatts of power, which accounts for an estimated 14 percent of the total capacity of 268 megawatts. While MECO technicians worked swiftly to restore power, Awai-Dickson explained the process took several hours in order to conduct an investigation “methodically, to keep the system stable.” Otherwise, she said, there would have been a risk of a sudden surge in demand, leading generators to shut down for a second time.
Some residents may have wondered why West Maui escaped the power failure. According to Awai-Dickson, West Maui was not affected by the outage because its transmission lines receive power from the Ma‘alaea power plant, not the Kahului power plant. While MECO provides service to nearly 60,000 customers on the islands of Maui, Moloka‘i and Lana‘i, its electric grids are compartmentalized. When you flip on a light switch, electricity is generated from a centrally-located power plant, or a power plant surrounded by major electrical load centers.
According to the U.S. Department of Energy (USDOE), a standard electric grid consists of two infrastructures: the high-voltage transmission systems, which carry electricity from the power plants and transmit it hundreds of miles away; and the lower-voltage distribution systems, which draw electricity from the transmission lines and distribute it to individual customers. The interface between the two infrastructures is the electrical substation, which contains transformers located along the distribution lines to “step down” voltage for household use. Substations, such as the one in Kihei, contain electrical switchgear and circuit breakers designed to protect the transmission system and transformers from potential electrical failures on the distribution lines. Circuit breakers are also located along the distribution lines to separate electrical problems, such as short circuits caused by downed power lines—or flashovers. However, the USDOE explained, a short circuit originating from a substation can cause a large-scale disruption in electric power supply, otherwise known as a blackout.
But as most of Maui’s power supply came to a screeching halt on Wednesday afternoon, many residents viewed it as an inconvenience—perhaps marginalized by prolonged water and power outages during last December’s Kona storm. Fortunately, no major injuries or incidents were reported on Wednesday. But the blackout served as yet another reminder for island residents to prepare for emergency situations. Simple precautions, such as keeping a reserve of flashlights, batteries, water and non-perishable foods, will ensure that when the lights go out, residents won’t be left powerless.