Temporary Earthing Newsletter - Issue 6
August 2008
The Temporary Earthing Newsletter is issued periodically to update the electricity supply industry on progress with research, testing and guidance on temporary earthing and the creation of equipotential zones. The Newsletter is prepared for the EEA by the Safety Strategy & Policy Group (SS&P Group).
EEA Safety Workshop
The annual EEA Safety Workshop is scheduled for late October. Date and venue details will be confirmed in the near future by EEA bulletin, and will be available on the EEA website.
The workshop will include updates on temporary earthing and the creation of equipotential zones for work on poles, and implementation progress and updates on the Guide to Work on De-Energized Distribution Overhead Lines.
Guide to Work on De-Energised Distribution Overhead Lines
The Guide to Work on De-Energised Distribution Overhead Lines has just been reviewed and re-published as Issue 3, and is available on the EEA website.
When Issue 2 of the Guide was published in January this year, it was limited to poles carrying conductors up to 33 kV only, with a note that guidance on poles carrying conductors at greater than 33 kV would be provided at a later date.
Issue 3 of the Guide includes guidance on poles carrying conductors at greater than 33 kV. It has been determined that coach screws provide a satisfactory solution for poles carrying all distribution voltages, but that there are circumstances when a downlead should be considered to enhance the effectiveness of the equipotential zone. In particular, where there is an elevated risk of relivening a downlead should be added in addition to the two coach screws. Guidance on the fitting of the downlead is provided in the Guide.
Particular issues are identified with downleads and discussed in the Guide. The Guide identifies that the fitting of downleads must take into account issues of feeding them through other in-service conductor sets, and careful consideration needs to be given to any decision to leave the downleads in-situ, e.g. the risks to live work and the possibility that the downlead may subsequently be used for equipment earthing.
The Guide is now complete and no further work on it is planned until it is next due for review. This completes the undertaking given to the Coroner inquiring into the Arahura fatality, at which the EEA undertook to, amongst other actions, carry out research, review it’s guidance material, and provide relevant information. The EEA also wrote to all CEO’s in September 2007 describing the actions which the EEA had taken, and the actions required of all companies working on lines, including implementation of the Guide.
The SS&P Group expects that asset owners and contracting companies will by now be well advanced with implementing the requirements of the Guide. The SS&P Group will continue to monitor implementation.
Guide to Work on De-Energised Distribution Overhead Lines Educational Resource
The EEA has prepared an educational visual presentation to convey principles and practices contained in the Guide. This resource can be used by trainers and others competent in the material, to familiarise field personnel and others with this subject. The visual presentation, current for Issue 3 of the Guide, will be available for purchase as a CD package. The CD Package will comprise:
- Issue 3 of the Guide (added to the CD for convenience, but primarily available at the EEA web site as a free download guide);
- Visual Presentation – Presenter Guidelines & Notes
- Visual Presentation in PowerPoint;
- Visual Presentation Handouts;
- Frequently Asked Questions;
- Comment & Feedback Form.
The PowerPoint visual presentation contains navigable contents that enable flexible delivery, whether specific Guide topics or the entire Guide content, depending on the need. The visual presentation includes, for example, coverage of equipotential zone principles, and a description of the Arahura accident electrical configuration.
The visual presentation CD is currently being designed and the contents compiled for CD reproduction. It is expected to be published between the end of August to mid September 2008.
Concrete Poles
The Guide identifies that concrete poles without integral earthing or an equipment earthing system cannot be included in the equipotential zone and need to be treated as partially conductive. The SS&P Group is pleased to see that some manufacturers are now providing concrete poles with integral earthing and fully endorses this development.
The SS&P Group is also aware of some research being carried out into the means by which existing concrete poles can be included in an equipotential zone. The SS&P Group is monitoring this work and will evaluate the results when they are made available.
Safety Award
The 2008 Workplace Safety Award was won by Connetics for their entry 'Responding to the Equipotential Zone Challenge' which showed a proactive approach to reducing the risks of harm from accidental relivening of overhead lines in the worksite.
The Connetics entry detailed simple steps to improve understanding and awareness of the safety issues and process, equipment, and procedures to minimise the impact of accidental relivening of overhead distribution lines.
Review of SM-EI Part 3
Work is presently being carried out on a review of SM-EI Part 3. The review specifically includes Part 6 on earthing, which will be reviewed to take account of the latest requirements for work on conductors. A consultation draft of the reviewed Part 3 is expected to be released in September and publication is expected before the end of the year.
Field Practices
The SS&P Group reinforces the priority which must be given to hazard identification, both at the work planning stage and when at the worksite. Temporary earthing and equipotential bonding is a necessary hazard control, but the focus must be on means to prevent inadvertent livening from occurring from any source including over or under passing live conductors and adjacent live conductors on the same structures.