Feb 2013
Electricity Distribution
Stay Rod Testing
Feb 2013
Northern Powergrid
Chris Goodhand, Innovation Manager (01977 605641)
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Innovation Funding Incentive
High Voltage Technology
The GB electricity distribution industry continues to use a stay wire, (anchor) rod and wood block combination to provide stability for Overhead Line (OHL) supports.

Stay wires and rods will, depending on a number of circumstances, degrade over their lifetime, typically 30 - 40 years. Failure of either can lead to failure of the support, which in turn can lead to a cascade failure of the line.

Currently the only reliable means of assessing the condition of entire rods is through excavation, but this is expensive and not always practical. Therefore once a defective stay wire has been identified Northern Powergrid need to be sure of the integrity of the stay rod, otherwise that will be replaced at the same time.

This is therefore extremely limiting and potentially restrictive to maintaining an active condition assessment profile of the stays and anchor assembly, as well as adding unnecessary costs to any replacement programme.

The project is a collaborative project to investigate the use of a Non Intrusive (NI) instrument for testing the condition of in situ OHL stay rods. EDM International Inc has developed an instrument that uses a magnetostrictive sensor. This is attached to the stay rod above ground level and provides a profile relating to the degree of corrosion in the rod below ground. The test instrument is to be used on a number of stay rods in GB and the results independently evaluated by EA Technology by recovering a sample of rods and testing in a laboratory to establish the accuracy of the test instrument (under predetermined, representative conditions).