ELECTRICITY DISTRIBUTOR National Grid Transco (NGT) has beefed up its transmission equipment checking system to head off a repeat of last year's mass blackouts in London and Birmingham.
It said this week that it had also boosted external communications to minimise disruption if there is a mass failure.
The moves are in response to criticism from power regulator Ofgem in a report published this week.
Ofgem said NGT did not breach its legal obligations and would not be fined, despite having made several mistakes.
But the regulator is to change NGT's licence so that the company will be automatically fined if there is a repeat blackout.
In London 500,000 people lost power for 37 minutes on 28 August when a substation shut down (NCE 4 September 2003).
The shutdown occurred after a voltage controlling shunt reactor ran low on oil.
Power was re-routed through a single substation in Wimbledon, but this overloaded a fuse causing it to shut down.
Investigators later discovered that a fuse triggering the shutdown was lower than the specified capacity.
A week after London, 200,000 customers in Birmingham lost power for 42 minutes when an engineer used the wrong diagram while carrying out work on a substation transformer.
This resulted in a mass power shutdown.
NGT has since checked 41,000 protection relays, 50,000 alarms and 560 multi function relays nationwide and made procedural changes.