Electricity Asset Management Plan 2019-2029
109
Vector Limited://
The graph below shows an age profile for Vector’s poles.
Figure 4-18 Age Profile for Poles (excludes 110 kV poles)
Condition and Health The average age of poles in the Northern region is 37 years and in the Auckland region it is 11 years. Vector has poles that have gone well past 60 years and are still in good condition. A large number of Vector’s concrete poles are the ‘Vierendeel’ poles – these are prestressed concrete poles that can develop hairline cracks that allow water and air to enter and corrode the steel strands. Strategy The failure modes, planned inspections, testing regime and maintenance activities for poles, conductors, crossarms etc. are described in Vector standard ESM401 Maintenance of Overhead Lines for example; before any Vierendeel concrete pole is climbed it is inspected and if showing signs of stress, is not climbed unsupported. Where steel is visible in poles it is red tagged for replacement. Where such poles excessively lean they are replaced. If a crossarm requires replacement the pole is replaced. If such poles exist in a part of the network in which a conductor replacement will take place (as per the programme of works described in Section 5), Vierendeel poles will be replaced. All new poles in the distribution network are concrete poles and all new poles in rights of way to customer premises are composite poles. Our CBARM model for poles and crossarms is under development at the time of writing and is not yet available to inform and enhance our intervention programme. In the meantime our tagging and replacement of poles based on our inspection and maintenance regime continues. However, where we undertake a conductor replacement, project poles are inspected and strength indexes calculated and replaced under the project if required.
4.4.3 DISTRIBUTION FEEDERS HV UNDERGROUND Overview
Vector’s HV distribution underground cables are a mix of paper insulated lead covered (PILC) cables and XLPE cables. The larger portion of distribution cables are rated 11 kV but in high density load areas such as Auckland’s CBD and the Highbrook industrial area the distribution voltage is 22 kV. The bulk of underground cables are in suburban areas but there are small pockets of underground cables in subdivision in more rural areas, e.g. north of Kumeu.
Made with FlippingBook - professional solution for displaying marketing and sales documents online