Tesoro Corp. said multiple power failures at the Kapolei refinery prompted the plant to shut units for maintenance and run others at reduced rates.

“The local power utility has confirmed that the grid is suffering from some instability due to bad weather,” Tina Barbee, a Tesoro spokeswoman at the company’s headquarters in San Antonio, said in an e-mail.

The plant shut some process units for work and is operating other units at lower rates, she said. The company reported an equipment failure at 12:05 p.m. Tuesday following a “power dip” at the refinery, according to a filing with the National Response Center.

The Kapolei refinery can process 95,000 barrels of feedstock a day, according to data compiled by Bloomberg. The company is “assessing inventories to make any adjustments to deliveries as needed,” Barbee said.