Timely Maintenance Maintains Value and Ensures Reliability
Prudent, properly planned maintenance is essential. There are a number of recent examples (Transpower) where infrastructure assets have been allowed to deteriorate through the postponement or avoidance of expenditure to the ultimate detriment of customers. We are adamant our network customers will not be placed in such a position. The management and maintenance of all our assets is governed by a 10 year Asset Management Plan that is available to view on our website (www.marlboroughlines.co.nz).
Over the year the Company spent $6.775m on maintenance which compares with $6.651m for the previous year.
Minimising Faults
From our perspective – and that of our customers – it is preferable that we undertake line maintenance and trim trees at a time of our choosing rather than having to repair consequential damage under storm conditions.
Our proactive approach not only provides increased reliability to our customers, it is also very cost effective.
Aside from continuous inspection we also utilise a number of measures to improve reliability.
We use thermo-vision equipment to scan transmission lines and substations to identify any joints exhibiting elevated temperatures.
We have continued to retrofit long length, non-standard possum guards which have proven very successful in eliminating momentary faults. All poles on 33kV lines and 11kV lines in forestry and bush areas, together with those in the Marlborough Sounds, have been fitted with special guards – in excess of 12,100 new guards have now been retrofitted. This has markedly reduced the number of supply interruptions at night and also reduced the potential fire risk.
Similarly, the retrofitting of plastic bird spikes on metal cross-arms in bird prone areas continues to be effective and line bark catches (developed within the Company) are valuable in preventing Blue Gum bark flashing over the insulators.
These measures, along with the installation of remotely operated circuit breakers, sectionalisers and the Supervisory Control and Data Acquisition (SCADA) – a system which includes in excess of 71 automatic phone-in devices, also developed within the Company – ensure that our customers enjoy maximum reliability.
The reality is, that our remote lines are radial and traverse difficult routes over rugged terrain so duplication of the lines is totally impracticable in terms of cost and access. Therefore we do our best to ensure all our lines are properly constructed, maintained and kept free from interference at all times.
The cost of tree clearance is a significant ongoing cost particularly in the Marlborough Sounds where growth is rampant and not only lines but access tracks must be kept clear. The Electricity (Hazards from Trees) Regulations 2003, require the Company to meet the full cost of the first cut or trim on trees identified as potential hazards. Costs for tree work totalled $1.156m last year compared with $1.429m for the previous year. The Company's GPS system proved a particularly valuable tool in track and vegetation control and for identifying property boundaries in areas where land ownership can alter without any discernible change.
Having taken all reasonable measures to prevent faults from occurring, the Company seeks to minimise outage time when faults do occur. Typically for the Marlborough Sounds and other remote locations the most cost effective first response is by helicopter, provided, of course, the weather is conducive to flying. When that is not the case we have to revert to boat and motorbikes, and in a number of instances the only way to gain access to our lines is by foot. Under these circumstances, regrettably outage times can increase, but it is worth knowing that around 20% of our customers are supplied from approximately 80% of our lines. Hence in most instances, the majority of our customers are unaffected.
In every instance, our response is assisted by good surveillance systems, including the virtual real-time NIWA satellite lightning tracking system which identifies the areas that need to be targeted after a lightning storm. Aside from minimising outage time this system is invaluable for customers who are absent from their properties; were it not for our surveillance their electricity supply could be discontinued and the contents of their freezers ruined.
We will continue to ensure that we make full use of emerging technologies (such as phone-in alerts and GPS) to identify and pre-empt problems on our network.
Overall, considering the background of our unique terrain and operating environment, our network reliability is good – particularly when faults caused by external sources such as cars and diggers are eliminated from the statistics and the impact of our remote lines are taken into account.
We take seriously the loss, or potential loss, of supply to customers during routine work. Wherever appropriate we use ‘live line' techniques or a large mobile generator to either eliminate or minimise disruption to supply. Regrettably though, some work cannot be undertaken live and this results in lost time shutdowns.
The average time lost by customers due to planned outages was 96.75 minutes for the year. This figure is higher than our target of 90 minutes and reflects the increased number of new connections, capacity upgrades and old asset replacements carried out during the year.
The total time lost in unplanned outages was higher than our target of 120 minutes, but at 153 minutes, it was lower than the 163.8 minutes recorded for the previous year. If faults due to the consequences of extreme storm events during a week of exceptional rain and winds at the end of July and early August 2008 are removed, then the fault record decreases to 97.61 minutes. This combined fault and planned result of 194.36 minutes is well below the combined target of 210 minutes. The adjusted level is lower than all combined values since 2000.
