Mitton Consulting has provided the EEA with a proposed testing programme for earthing solutions for work on poles which has been approved by the SSPG.  Mitton Consulting is also carrying out earthing arrangement tests on poles for Transpower prior to commencing the testing for the EEA. Testing for Transpower has commenced, and testing for the EEA is scheduled to commence by late August.

The primary objective of the tests is to identify a practical means of establishing an effective equipotential zone at pole worksites.  Specific objectives are:

1.     Testing specific potential solutions for temporary earthing and creation of equipotential zones.
2.     Confirming the degree to which the tested solutions will provide worker safety in a range of conditions likely to be encountered in NZ, either by themselves or in combination with another tested solution.
3.     Gauging the practicality of the tested solutions.

1.     Cluster mounts.
2.     Earth stake driven against the base of the pole for existing poles, and butt wrapping of new poles.
3.     Spiking of the pole (at approximately 1.5m above ground level).

The annual EEA Safety Workshop is being held from 12-13 October at the Kingsgate Hotel in Hamilton.  At the workshop it is hoped to provide an overview of the test results, depending on the results (or some of them) being at a stage where they can be conclusively presented. 

Target Dates and Planned Dissemination of the Earthing Guide

•     Field tests complete by end of September.
•     Analysis of results, and approval by the SSPG, by late November.
•     Preparation of revised draft guide for temporary earthing by end of January 2007.
•     Industry workshops in February 2007.
•     Finalisation of guide for temporary earthing by end of March 2007.

The SSPG is currently undertaking a review of the temporary earthing requirements for mobile plant working in the vicinity of live conductors.  Advice on temporary earthing for mobile plant in switchyards is reasonably well catered for, but advice on mobile plant near conductors other than in switchyards isn't.  Examples of such use include tree trimming and use of cranes.  The term 'near' means within 4m of live conductors.

Advice is being prepared recommending the use of conductive mats bonded to the mobile plant, and the use of temporary earths for mobile plant.

The SSPG is preparing an overview of temporary earthing practices and requirements for distribution overhead lines, to ensure that the principles for temporary earthing are documented.  The intent is that the overview will be made available to the industry when it is completed as a means of explaining the background to temporary earthing practices, and to ensure that necessary guidance and training materials are provided.

The SSPG reminds the industry that the Notice to Industry (Work on Overhead Conductors) published in September 2005 is still its latest and most relevant guide on temporary earthing.  

The SSPG also reinforces the priority which must be given to hazard identification.  Temporary earthing and equipotential bonding is a necessary hazard control, but workparties must focus 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.