Feb 2013
Electricity Distribution
Stay Anchor Testing Using Magnetostrictive Sensor Measurements
Feb 2013
Electricity North West Limited
Electricity North West Innovation Team
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Innovation Funding Incentive
High Voltage Technology
Historically, GB has used and still continues to use a stay wire, anchor rod and wood block combination to provide stability for overhead line supports. Ideally the stay angle to the structure should be at 450 to the ground with the block buried in the ground to a depth 1.6m – 2.0m depending on the duty and angle of the stay. The rod is 2.5m in length and attached at the top to an adjustable head. The stay rod will, depending on a number of circumstances, degrade over its lifetime, typically 30-40 years, which can lead to failure of the rod and the stay combination. This presents an increase in safety risk to our staff and members of the public, in addition to the financial risk should the failure of the stay combination result in a support failure. Other than digging around the area of the stay rod, which is not necessarily practical, there is no recognised method of testing within the GB Power Industry to identify corrosion of the rod below ground. This is therefore extremely limiting and potentially restrictive to maintaining an active condition assessment profile of the stays and anchor assembly.
The objective is to provide recommendations as to how successful and/or practical the tests have been and whether there is scope to consider using this non-intrusive technique for routine inspection of stay rods in the future. The current time based approach to stay road anchor maintenance and replacement is time consuming and may be delivering the optimum results.