Non-intrusive Tower Foundation Assessment

Maintaining the integrity of a steel tower overhead line is vital to ensuring reliability of the electricity transmission and distribution network, with a key component of the steel tower overhead line network being the concrete foundation.

Traditionally, tower foundations can be excavated to allow inspections to take place, however, this method can be disruptive, time-consuming and expensive.

The value of non-intrusive techniques is to provide general information on the state of foundations and identify individual towers within a group which are most likely to have suffered significant steel corrosion and/or below ground concrete damage.

Business Benefits

• Cost-effectively prioritise the tower foundation inspections
• Significantly reduce the number of excavation inspections
• Identifying the towers at most risk of significant corrosion damage in the future
• Concentrate limited resources on the most relevant towers
• Increased confidence in the overall condition of the tower foundations for a given route.

Assessment Methods

EA Technology has developed a selection of assessment methods that allow a certain degree of flexibility, which is essential due to the significant variation in foundation types across a typical operator’s network. Different inspection methods can be selected depending upon the outcomes required. The individual inspection methods are as follows:

• Visual inspections
• Corrosion Current and Voltage Potential
• Transient Dynamic Response and Time Echo Response
• Soil Resistivity
• Soil Chemistry
• Redox Potential

Summary

The results of the inspections and measurements recorded can be combined and used to estimate the likelihood and rate of future corrosion, and therefore present recommendations regarding the need for excavations and/or refurbishment.

Condition ratings can then be applied to each tower leg in order to prioritise for excavation or remedial work, should it be required. All results are presented as colour-coded ‘traffic lights’, together with a photographic record of tower muffs to make it quick and easy to identify towers that are at risk.