The monster electrical equipment will crawl at 12mph as it makes its way from Tilbury Docks in Essex to West Weybridge substation in Surrey.
The 56 mile journey will take so long as the equipment will be transported on a specialist vehicle which is more than 68 metres long and 5.3mph.
The journey starts at 7pm on Friday August 17 and ends at 4pm on Sunday, August 19. It includes includes a 26 hour stop at Clacket Services from Saturday at 4am, so it can finish the route on Sunday when there is less traffic on the road.
National Grid has sent letters to residents warning of potential chaos.
It has even had to trim hedges to make sure there is enough space to move the transformer through, with local roads also making up some of the route.
The 143 tonne lorry needs to divert off the motorway as soon as it crosses the Queen Elizabeth bridge to snake through local roads due to a weight restriction between junctions 1A and 2 of the M25.
The transformer will be used to deliver electricity to the south of England.
Most of National Grid’s substations were built between the Fifties and Seventies and equipment such as transformers need to be replaced to keep them working efficiently.
New transformers are also installed to connect new sources of generation or when demand for electricity is growing.
Aleksandra Zefirova, National Grid Project Engineer said: “Our network operates smoothly, safely and efficiently over 99.9999% of the time – a statistic we’re very proud of. Millions of people rely on us to supply their electricity without interruption, day in, day out and so it’s important that we keep our substations and the equipment in them working efficiently.”
The transformer’s route will be:
- From Tilbury Docks on the A109 north until it meets the A13.
- West along the A13 to the A1306.
- A1306 until the junction of the A282, towards the QEII bridge on the Dartford Crossing.
- Exit the at junction 1A and go along the A206, B255 and A2 before rejoining the M25 at junction 2.
- Exit M25 at Clackett Services between junction 5 and 6 for 26 hour break.
- Rejoin M25 until junction 11 and onto the A320 south.
- Turn to the A245 and B385 Woodham Lane.
- Turn into Pinewood Grove, then left into Parkside and into the substation.
Anyone with information about the delivery can call the National Grid hotline on 0800 019 3235 between 9am and 5.30pm or email email@example.com.