Aurora Energy is introducing pole reinforcement technology in selective cases to reduce the risk and extend the life of wooden power poles across its Dunedin, Central Otago and Queenstown Lakes area networks. Pole reinforcement is a proven and effective alternative to replacing the pole, that allows the upgrade to be done quickly and, in most cases, without the inconvenience to our customers of turning the power off.
Pole reinforcement is one of a number of methods used to remove the risk of poles
Aurora Energy and its contractors have a number of methods at their disposal to remove the risk of identified poles as part of Aurora Energy’s Fast Track Pole programme from repair to complete replacement. These options include:
- Replacement of the old pole with a new one
- Making repairs
- Reinforcement of the pole
- Retest the pole using an independently verified testing method and where assessed as sound, update its condition assessment.
As well as providing a proven and effective alternative to replacing the pole, reinforcement also allows the upgrade to be done quickly and, in most cases, without the inconvenience to our customers of turning the power off. Inspectors may also reassess the pole’s condition using a verified testing method, then either replace or repair the pole or update the condition as merited.
The Fast Track pole programme is well advanced, by the end July 2017 1,600 of the 2,910 poles due for remediation had been completed. With up to 20 crews working throughout the region we remain on track to complete the remaining poles by the end of year. We expect of the 2,910 poles, about 900 will be reinforced, the remainder will be replaced, repaired or reassessed.
Pole nailing reinforcement is a common practice and conforms with Australia/New Zealand standards
Pole nailing reinforcement is common practice in a number of countries including Australia, has been used in New Zealand for several years.
The technology Aurora Energy selected was developed in the United States and has been in use in the industry for over 50 years. The process meets the Australia/New Zealand standard and includes an engineer assessing and confirming the upgraded strength of each individual pole as part of the reinforcement. Prior to its introduction, Aurora Energy carried out a risk assessment and evaluation including external advice and review.
Pole reinforcement is a recognised and approved method under both the Australia/New Zealand standard AS/NZS 7000: Overhead line design – Detailed procedures and the Electricity Engineers’ Association of New Zealand’s Guide to Work on Poles and Pole Structures (August 2016).
Aurora Energy has brought in specialist resource
Aurora Energy has brought in Australian pole reinforcement company Logsys Power Services, specialists at evaluating poles strength and suitability for restoration. Logsys uses Osmose trussing systems which are engineered for safety and reliability and have been thoroughly and independently tested and proven throughout their 50-year history.
How pole reinforcement works
The system restores a wooden pole back to its original below ground strength. It involves installation of a steel truss which is driven to between 1.5 metres’ to 1.8 metres’ depth next to the pole and secured with metal banding. The size of the truss depends on the height, location and loading of the pole being reinforced. The system can extend the life of the power pole by between 20-30 years.
Only a fraction of Aurora Energy poles are selected for pole reinforcement. Before nailing, each pole is assessed to determine if it is suitable for this form of mitigation. The assessment requires a number of technical, safety and practical parameters to be checked. Only then is nailing confirmed as a suitable option.
Questions
1. Does pole nailing reinforcement weaken foundation supports?
Where wooden poles have a below-ground support, the truss is installed to avoid it. If the truss cannot be installed without damage to the support, the pole will be not be nailed, and replaced instead. If the support is undetected and damaged in the course of nailing, the pole will be replaced instead.
2. Does the pole nailing reinforcement process affect adjacent poles?
The specialist equipment used to drive the truss beside the pole results in minimal vibration to the pole, overhead conductors (power lines) or neighbouring poles – about the same effect as a light to moderate breeze.
3. Why reinforce below ground?
All wooden poles deteriorate as they age. Over time wooden poles rot just below the ground where oxygen and water are both present. The pole butt deep in the ground and the portion of the pole well above ground remain sound for years after the decay starts at ground level. Pole reinforcement substitutes the decayed portion of the pole with a steel reinforcement that restores the strength across the decayed section of the pole, extending its serviceable life.
4. Are reinforced poles safe to climb?
Yes, reinforced poles can be safely climbed by trained lines workers, but under Electricity Engineers’ Association safety guidelines, line workers must check every pole before they climb or work on it. The same guidelines include pole nailing as a recognised and approved method for reinforcing wooden poles. Aurora Energy has requested all contractors working on its network review their pre-climb work practices to ensure they have a robust process in place for reinforced poles as well as other pole types.
5. How do ground conditions affect pole reinforcement?
Soil types vary significantly around New Zealand and within Aurora Energy’s network. The type of soil has a significant bearing how much load a pole can support safely, before it sinks into the ground or starts to lean over. The Australian/New Zealand standard provides guidance on how to factor various soil types into the design of overhead power lines and is applied in the same manner for wooden poles, reinforced wooden poles and concrete poles.