04/04/2024
Sample piece of 33000 Volt Oil Fillled Cable.
These cables were installed on the Southern Region AC Distribution Network from the early 1950's. The average cable length is around three miles, Substation to Substation.
The cables were pressurised with oil, which acts as an insulator having impregnated the paper insulation, and also a coolant. This sized cable was rated around 400 Amps.
As the cable heats up and cools down the oil expands and contracts, and is stored in tanks along the cable route. These oil tanks often resemble giant mushrooms.
There are pressure switches on the oil tanks which are remotely monitored in the ECR. On receipt of a Low Oil Pressure Alarm, arangerments are made for the cable to be pumped back to pressure, or switched out depending on the situation.
This type of cable is highly maintaince intensive, and has numerous environmental issues due to leaking oil.
A large proportion of these feeder cables have been replaced with XLPE.
There are still many around, but are being replaced with XLPE under a rolling program.