The fire on a cable bridge led to the widespread power cut
Engineers are still working to restore electricity to about 66,000 homes on the south-east London/Kent border.
Up to 100,000 properties in Erith, Orpington, Dartford, Bexleyheath and Crayford were left without power after a suspected vandal attack.
A fire on a cable bridge damaged four major electricity circuits on Monday.
EDF Energy worked throughout the night to restore power and set up generators but it anticipated some would be without power until Wednesday morning.
EDF is supplying electricity from its mobile generators in a rotation system giving customers access to supplies for up to three hours at a time.
On Tuesday the Highways Agency suspended all charges on the Dartford-Thurrock River Crossing to "reduce congestion".
"All safety systems on the crossing are unaffected by the power outage," it added.
The blaze took hold of a cable bridge over Dartford Creek at 1247 BST.
Locks on the security gates at both ends of the bridge had been broken.
Kent Police, which is investigating the fire, have deployed additional patrols as the repair work continues.
Ch Insp Peter Ayling said: "We have committed significant resources to investigate the cause of the incident and inquiries are ongoing.
"It unclear at this stage whether this was criminal damage to or attempted theft of high voltage cable."
An EDF Energy spokeswoman said: "We have managed to restore supplies to about a third of customers and will provide temporary supplies to more customers while we continue repairs.
"We continue to work on a full restoration of power supplies.
"However this is a complex and difficult situation and it is unlikely this will be completed before tomorrow morning."
Shops, banks and petrol stations have been hit
Darent Valley Hospital in Dartford was also affected by the power cut.
But a spokesman said there was sufficient power to run the whole hospital from a back-up generator.
A spokeswoman for Kent Police said: "Kent Police is working with partner agencies to ensure normal services are restored as quickly as possible and are investigating the circumstances leading up to the power failure."
A spokesman for Dartford Borough Council said there had been no disruption to essential services.
Kent Police said the power cut had affected several petrol stations and people were being urged to fill up their cars outside the affected areas.
EDF Energy's emergency helpline number is 0800 028 0247
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