Inmates at Wooroloo Prison Farm have set a number of small fires during a power outage at the facility, north-east of Perth.
The WA Department of Justice says the fires were lit away from buildings on Wednesday night but were quickly extinguished by staff.
There were no injuries and no damage and power to the perimeter security systems was not impacted by the outage.
Electricity supplies were restored to the entire facility by midnight.
The department said prisoners who took part in the incident would have their security rating upgraded and would be moved to a higher security jail.