When your power goes off without warning you probably want to know when it will come back on, rather than what caused the cut. But it’s very important to us to know where the problem is, as it affects how we can get your power back on.
Most customers use electricity at 230 volts. As electricity at this low voltage only travels a short way we have many local substations where the power comes in at a high voltage (usually 11,000 volts) and then reduces to the low voltage (230 volts) you use at home.
Faults can occur on both our high voltage and our low voltage network.
High Voltage faults
A high voltage fault can cut the power to several thousand customers over quite a large area. We generally know when high voltage faults occur because most send an automatic alarm to our control centre.
To restore power:
- We work outwards from the main substation, which often means that power is first restored to customers living nearer to the source
- We split the circuit into sections enabling us to switch the power back on in stages once each stage is checked
- We use your normal circuit or an alternative means of a connecting switch.
Our staff travel to site to investigate and work as quickly and safely as possible to restore power. We’re installing more remote-controlled switches to improve our service.
If we need to do more extensive work to repair a fault we may connect you to a mobile generator.
Low Voltage faults
Low voltage faults usually affect just a few customers in a small area. They often don’t affect everyone in the same area.
If you are the only customer to call us we will come to your home to check our electrical equipment. When you call our emergency number our agent will tell you that we make a charge if the problem turns out to be on your electrical installation.
There are three types of fault that can occur:
- A permanent short circuit requires us to repair the fault which might take several hours if it is difficult to find or a lot of excavation is necessary
- A permanent open circuit can often be bypassed so we can restore power from an alternative source and clear the problem later
- An intermittent short circuit is a temporary fault that can be cleared quickly but which might develop into a more serious fault