Scotland Region Temporary Instruction – SICAT OLE variant Isolation Earthing Temporary Instruction
Instruction dates – 27th of August 2021 until further notice
BACKGROUND
Network Rail and the SICAT OLE equipment manufacturer are currently investigating a high impedance component affecting the earthing of the following electrical sections:
- EG5 and 6 (subsections EG5J, M and N and EG6A and A1 only)
- EB1-5
- EK1 (subsections A and Q only)
- EL1 and 2 (subsections EL2A and EL1D only)
- MH2
- MH1G only
ACTION TO BE TAKEN
The below applies to all earthing locations within the detailed affected sections and limits:
- Short portable earths to be erected as per NR/L3/ELP/29987
- One supplementary long portable earth to be applied between the traction return rail and the catenary wire (not the contact wire) on each affected electrical section at all earthing locations.
POINTS FOR CONSIDERATION
- There is no requirement to apply supplementary long portable earths on the return conductor.
- Care must be taken to apply the long portable earths to the traction return rail. There are more than two lines in some areas affected by this instruction, and not all of these will have a structure to rail bond. The Authorised Person/Nominated Person may have to walk to the nearest track to track bond to identify the traction return rail and follow this back to the earthing location.
- It may not be possible to tie all long portable earths back to prevent them fouling the running line. Nominated Persons must consider the passing of any Trains/OTM/OTP through the isolation and how this is managed.
- Alternative mitigation methods may be acceptable with agreement from the Electrification and Plant Maintenance Engineer.
