The Luas Green Line in Dublin remains out of service on Thursday morning following a major power outage.
In a statement, Luas customer service said engineers have identified the fault lies within a “critical low-voltage safety system known as the 48-volt system”.
“This is not the overhead power system that powers the trams. Rather, it is part of the safety network that links substations to the central control room and allows power to be safely controlled and monitored across the line,” it said.
“In simple terms, this safety system is designed to shut down power to the overhead lines in the event of an emergency. The system is currently detecting a fault condition and, for safety reasons, will not permit the power to be fully restored until that condition is resolved.
“As a result, services on the Green Line remain suspended while repair work continues.”
It added that multiple Luas technicians are working to resolve the issue and restore power.
The problem emerged on Wednesday when services were also out of action for most of the day, causing disruption for thousands of commuters and other users.
The Green Line links Boombridge on Dublin’s north side to Brides Glen, near Cherrywood, in the south, crossing the city centre.
Luas tickets are being accepted on Dublin Bus during the outage and Red Line services are running as normal.