Open letter to Hanmer customers

On behalf of MainPower, I would like to apologise for the impact the unplanned electricity outage on 12 August had on some Hanmer Springs residents.

It was never our intention for Hanmer Springs to go without electricity for this duration. As communicated prior, we had critical network maintenance we needed to complete to allow us to address possible failure points of electricity supply to the region. This had been scheduled for earlier in the year however the impact of Covid-19 resulted in us having to delay.

We sought feedback from customers in the Culverden, Mouse Point and Hanmer Springs areas as well as electricity retailers and Fonterra (on behalf of dairy farmers in the region), and looked into a number of

options, including:

  • Moving the outage to later in the year. This was not deemed feasible as the irrigation load on the network is too high to be managed with generation.
  • Moving the outage to next year. This was not feasible due to the criticality of the work needing to be completed.
  • Increasing generation to enable the work to be carried out with minimal disruption to customers. This was the preferred option and was in line with the feedback we had received from customers and industry representatives. The lower load on the network at this time of year made generation feasible compared with other times of the year.

MainPower engaged an experienced subcontractor to provide generation to cover the scheduled maintenance from 11-13 August 2020. This obviously came at a substantial cost to MainPower, however we believed this was acceptable as we wanted to lessen any impact on our customers. We used a reputable subcontractor who we have worked in the past and is a global player in the generation services market.

The subcontractor was responsible for the generation for the full works period. Four generators were supplied to ensure there was more than enough electricity to manage the load of Hanmer Springs at this time of year and allow us to carry out our work safely. These four generators were connected to two of their transformers to allow all of Hanmer Springs to be supplied with electricity.

Unfortunately, one of the transformers experienced a major failure that could not be fixed, this meant two of the generators could not operate. The remaining two generators and transformer were not able to supply enough electricity for all of Hanmer Springs, this is why electricity was only able to be restored to parts of the central business area. We searched for another transformer all over Canterbury including asking other lines companies in the South Island, however we were unable to source one and have it installed before the end of the day.

This incident is classified as a network fault, it was beyond MainPower’s control. At the point when the generators and transformer failed, we had already commenced the critical work. On its failure and the understanding that it could not be readily fixed by the subcontractor, we decided to cease the remaining planned maintenance and focussed our team on finishing to allow us to reconnect Hanmer Springs as quickly as possible.

MainPower is in the process of addressing this with the subcontractor in relation to the issues experienced and is investigating what caused this failure. We are incredibly disappointed by this situation and that our customers feel let down by MainPower and our subcontractor.

It is necessary for MainPower to complete network maintenance on the network as required to maintain reliability and safety. While we cannot guarantee electricity is supplied 100% of the time, we try to minimise the impact on our customers where possible. Unfortunately, even with appropriate plans in place for this work, we failed to achieve this and for that we apologise.


Andy Lester

Chief Executive