UK BP/SE/NSI 24

1. UK BP/SE/NSI 24 Colin Hepton Keadby 400kV Substation

2. Scope Approaching and Working on Earth Systems (and associated conductive parts). Incorporates TGN(T) 114 - Replacement of stolen Earth Tape. Additional Procedures for work on Railway Operator Connections.

3. Definitions • Earth Bond - Bonds for purpose of providing Earth Continuity on Earth Connections. • Approved Earth Bond and Pole - Detailed in TGN(T) 114 and are used to make/break connections in Main Earth Systems. Not rated for System Fault. • Main Earth System - Arrangement of interconnected buried or surface conductors providing an electrical connection to True Earth, which are intended to carry HV fault current. • Other Earth System - Earth Conductors which are part of the system but which are not part of the Main Earth System. • Intact System - Any Earth System in which there are no breaks in the Earth Conductors. • Inadequate System - Any Earth System in which there are breaks in the Earth Conductors. • Poor Weather Conditions - Lightning, Snow Storms, Heavy or persistent rain, fog or mist.

4. Dangers • Differences in Potential (including Step, Touch and Transferred - steady and fault) across the Earth System in which parts are incomplete, segregated or without continuity. • Flying Debris due to faults on equipment that is inadequately Earthed. • Rise of Earth Potential from Earth Faults on adjacent systems currents which flow in Earth Systems.

5. General Principles to avoid Danger. • Any part of the Earth System must be considered to be an Electrical Conductor • Work must be carried out by a Competent Person under an appropriate Safety Document • Disconnect associated equipment from sources of electrical energy which could give rise to danger • Bonding across before making or breaking any Earth System connections • Insulated Working • Ensure that remote earths are not introduced which could be at a different potential to local earth

6. Approaching and Working (1) • No restriction when approaching intact Earth Systems. • For Inadequate Earth Systems: • Concrete Structures • >10m where there is risk of system fault • >1m where there is no risk of system fault • In an emergency <10m is permissible, but >1m must be upheld.

7. Approaching and Working (2) • For Inadequate Earth Systems • Metallic Structures • <1m approach is prohibited • Same for Surge Arrestors and Cable Sealing Ends (where they are independently earthed) • Buried Earth Tape • <1m SAP must perform a RA and identify precautions to avoid Danger

8. Approaching and Working (3) • Working on Main Earth Systems • Make/Break connections can only be made after they have been bridged using a connection of equivalent current carrying capacity, unless RA indicates no significant hazard • Other Earth Systems • Requirement for RA applies, any Earth Bond must be appropriate for duty.

9. Limitations • NSI 24 not suitable for: • Attachment to copper braided/multistranded conductors. • Repair/connection/disconnection to tape between substation and terminal towers

10. Application of Earth Bonds to Main Earth Systems • Application/Removal should not occur where there is an increased risk of a System fault. • Only Approved Earth Bonds and Poles should be used. • One end should be connected to an intact Earth System. Approach <1m can be made to do this, but the Earth Bond should be between person and connection point. • Earth Bonds should not be relied upon for t>2 months.

11. Application of Earth Bonds to Other Earth Systems • RA and control measures identify the Earth Bond to be used and its application. • Order of application and removal should also be made clear.

12. Testing • Testing of Earth Systems should be made in accordance with a Method Statement and RA. • Flowchart for use when making RA.

13. THAT’S ALL FOLKS!