Fluid filled cable hydraulics

Paper insulated oil filled power cables, with a service life of 60 years or more, remain in service around the world . The insulating oil within these cables must be maintained at a positive pressure for the cable system to operate reliably.

The cable’s oil pressure will change with changes due to ambient temperature and conductor heating when the cable is in service. Pressure accumulators (known as oil feed tanks) are installed on the cable system to maintain the oil pressure within acceptable service limits. The correct type and size of feed tank used and the oil feeding system pressure and alarm settings must to be determined when the length of the oil filled cable system changes, for example due to circuit diversions or insersions of soilid dielectric cables (such as XLPE).

CCI provide cable system hydraulic calculations hydraulic calculations for system owners, developers and mainteners of circuits containing oil filled cable systems.

Traction feeders for the UK rail network include a significant quantity of 33kV three core oil filled cable. In order to increase the power supply to the network the introduction of additional substations along rail routes requires that the oil filled cables be diverted into these substations. 33kV oil filled cables are no longer being manufactured and it is thus necessary to divert the cable circuits using soilid dielectric cable (XLPE) and transition joints. These circuits have included multiple oil sections, stop and feed joints, trifurcating joints, splitter joints and MIND tails. Such diversions often require new pressure settings and oil feed tank relocations.

CCI have provided revised calculations for numerous railway circuit diversions.

Our capability includes calculations for oil filled cable circuits from 25kV up to 525kV.