Power outage figures from Waipa Networks confirm what Tamahere residents have long suspected – the area has more than three times as many outages as the rest of the Waipa network.
In the last year, Tamahere people experienced, on average, a high eight hours without power compared to around three hours for the network as a whole.
The figures have been revealed to Tamahere Forum after a power outage in late April that for some locals lasted six hours.
Waipa Networks customer services manager Kerry Watson, who provided the figures to Tamahere Forum, said the biggest cause of outages is the area’s many trees.
The lengthy outage in April was caused by an uncommon failure of isolation equipment in a cabinet in Birchwood Lane. And things like equipment failure, car accidents and bad weather did cause a percentage of outages in Tamahere each year.
But by far the most frequent cause was trees interfering with the lines, Watson said.
Tree owners have obligations to ensure that their trees do not interfere with the power network.
“We have particular difficulties in negotiating tree cutting in the Tamahere area as one of the reasons residents choose the area is the trees,” Watson said. “Tree owners are therefore reluctant to have them trimmed or to take responsibility for keeping them clear of our lines.
“However, due to the particular problems in this area we are increasing our tree liaison and trimming work in Tamahere,” he said.
Waipa Networks posted a brochure about trees and powerlines to all of its customers in April and had had a good response from tree owners. Click the following link for a copy of the tree brochure(PDF): Waipa Networks trees & powerlines
“We have already trimmed two sets of problem trees in the Tamahere area,” Watson said.
Waipa Networks was having a renewed focus on tree trimming, particularly in the Tamahere area, and hoped to see a significant reduction in the number of tree-related faults, Watson said.
What the figures show
One of the key indicators of the reliability of an electricity lines company is the System Average Interruption Duration Index (SAIDI). The figure is arrived at by adding up all the customer outage durations and dividing by the total number of customers supplied to give an outage figure in minutes per customer.
From April 2014 to March 2015 the Tamahere power feeder had a total of 896,694 customer minutes without power. There are 1850 customers supplied by that feeder and so 896,694 minutes divided by 1850 customers equals 484.7 outage minutes or around eight hours per customer over the 12 months.
However, overall on the Network, the outage figure was 172.10 minutes (around 2 hours 50 minutes) or around five fewer hours of outage than that experienced in Tamahere.
The 2014-2015 year was not unique. 2011-12 was also a bad year across the network but especially for Tamahere.
On the graphs, the outages in blue are faults caused by trees, whereas the items in red include things like equipment failure, car accidents, bad weather, and unknown causes but possibly trees also.