* 300,000 bpd plant back to normal on Friday
* Brief upset occurred with other plant in region down
CALGARY, Alberta Aug 12 Irving Oil Ltd's New Brunswick refinery, Canada's largest, had a brief operational upset on Thursday, but operations were back to normal on Friday, a spokeswoman said.
"We had a minor upset briefly yesterday. But there are no production problems at our refinery. It's normal operations here and business as usual," Irving spokeswoman Carolyn Van der Veen said in an email.
The Saint John, New Brunswick, refinery has a capacity of 300,000 barrels a day. It is a major supplier of fuels in the U.S. Northeast.
Word of the outage set energy traders on edge as it coincided with a planned shutdown at an Atlantic Canadian plant, Imperial Oil Ltd's (IMO.TO) 82,000 barrel a day refinery in Dartmouth, Nova Scotia. (Reporting by Jeffrey Jones; editing by Janet Guttsman)