Eighteen-year-old Ericsson equipment is being replaced with equipment and applications from Damovo which were originally designed for stock exchanges.
Because telephone contact is essential to ensure that workers are not harmed by wrongly-timed switching of high-voltage electrical equipment, calls are routed and tagged according to type and priority, with details of the caller appearing on the dealer board.
Paul Guest, Damovo's account manager for the National Grid, said, "It is absolutely mission-critical. Controllers need to be in contact with substations over maintenance and other issues and, for example, cannot switch on when there is a human being in the area."
He added that the switching equipment is IP-enabled but at this point it was felt better to stick with PSTN technology because it was tried and tested.
Guest said the challenge was to devise a system which gave the same type of prioritisation of calls as the original Central Electricity Generating Board specification, while also being upgradeable to work with IP and computer telephony integration applications in future.
The network will serve three regional control rooms, eight switching centres and interface with nearly 300 substations.