World War workings
A complex initiative to replace a post Second World War 33kV network is underway in the city of Plymouth.
The project involves renewing 48 kilometres of cable over 17 circuits and will be worked on by five jointing teams over the next four years.
Part of the 48km of excavations that will need to take place.
Project Engineer Gary Beasley, who is overseeing the scheme, said it is probably the area’s single largest project based on the amount of excavation work, its timescale and financial value.
“Our teams, working alongside contractors, have used a range of equipment including five tonne diggers and nine tonne dumper trucks to replace existing circuits with a mixture of varying-sized cable,” he explained.
“All the trenches are a metre deep, which means we can keep 900mm of ground above the cable and the ducts to reduce any risk of damage. Once this project is complete, Plymouth’s entire 33kV gas cable network will have been replaced.”
The use of gas cables over oil-filled cables was preferred in the immediate post-war era due to the topography of the area. The cables are nitrogen filled, to keep them cool, help insulate the joints and increase running capacity of the circuits.
While the work will greatly benefit the area’s network security, the project to date hasn’t been without its challenges, as Gary explained.
“The main consideration is that the bulk of our excavations are in roads in and around the city and so while they take place we’ve taken care to ensure we maintain good traffic movement with minimal disruption.
“We’ve also been liaising with local businesses to keep them informed and to minimise the impact of our work as much as possible, and we’ve also planned our schedule to match with university and school holidays.”
Planned outages which coincide with the installation of new cables as circuits are completed, are set to continue until 2020.
Gary explained: “The next stage of the project is to excavate a 700mm directional drill under the main, six-lane A38 which runs through the centre of Plymouth; it is planned to be completed by the middle of this year.
“We’re working closely with the local highways department and liaising with the city council and local councillors to keep them updated.”
Plymouth Linesman Matt Webster working on the gas cables.