Scope
Decommissioning of high-voltage oil-filled cable circuits across the National Grid transmission network in the United Kingdom. The scope covered cable sections up to 275kV. Project duration: 20 weeks per treated section from first injection to final verification, with prolongation because of outage window works from contractors.
Methodology
bionrec applied the four-phase ODB process. Phase 1 profiled each cable's oil chemistry and screened for PCBs to design the bacterial treatment plan. Phase 2 injected cultures selected for dielectric-oil biodegradation directly into the cable's oil channel through existing access points. Phase 3 ran the bacterial degradation over repeated injection cycles, with bio-surfactants releasing oil trapped in the paper insulation matrix. Phase 4 verified removal efficiency through post-treatment sampling before the cable was left safely in the ground.
Result
Cables were left safely in the ground. No excavation, no civil works, no hazardous-oil contamination risks. ISO 17025 lab verification and documentation covering removal efficiency was showing great results of 98,6% of oil removal from the paper matrix.
"(...) prove that the proposed technology can be applied for transmission, then the decommissioning time, excavation and other required civil work for fluid-filled cables could be reduced dramatically. This would in turn lead to significant reduction in disruption to the local communities and local traffics. The environmental risk for potential oil contamination is also much decreased."