Transpower says it achieved two New Zealand firsts the past year with the implementation of its demand response programme and the commissioning of the largest mobile substation in Australasia.

The six-month demand response programme involved eight participants who registered to provide 134 MW of load for curtailment, more than the 100 MW targeted and equivalent to the winter power demand of New Plymouth.

Curtailment was called on 20 times, with no participants missing an event due to lack of notification. The largest call, of 175 MW, was an unplanned event during the HVDC Pole 3 test programme. A shortfall of generation that day required a quick response.

Transpower says the success of the programme was due to the Demand Response Management System (DRMS) it developed with Alstom Grid.

The grid operator says earlier studies had shown a simpler mechanism was needed to lower the threshold for firms wanting to participate in such programmes.

The DRMS is a simple computer-based open system that doesn’t require any significant investment by end-users and is easy to operate.

The demand response operator initiates an event, with emails and web service feeds then sending the relevant information out to participants. Coordination with the system operator and local lines companies is then conducted with agreed procedures, including phone calls and emails.

Transpower says the DRMS was key to aggregating the multiple smaller commercial loads necessary to keep demand response economic. The system was future-proofed to ensure that ultimately residential customers could also be accommodated.


Transpower’s other big innovation was the 113-tonne mobile substation it put on the road last year.

The 40-metre, two trailer unit is the largest in New Zealand and possibly Australasia. It is capable of doing all the jobs of a normal substation while also being road and ferry compliant and able to access any one of Transpower’s 14 single-unit grid sites.

Transpower says the driving motivation for the project was to minimise the cost and disruption faced by communities served by those ‘n’ sites. The sites have only a single point of supply and once a year face a day without power and the disruption to business and tourism that results from annual maintenance requirements.

Transpower says the two main innovations within the project were in the construction of the transformer and the switchgear.

It was necessary to keep the weight and dimensions of the transformer to a minimum, meaning electric stress and temperature gradients had to be pushed higher than normal. This was achieved through the use of synthetic insulation, stress control structures and new plug-in bushings used for the first time at 110 kV.

High-voltage switchgear was also needed to connect the transformer to the incoming overhead line in a cost-effective manner. This involved reducing the height, designing new moveable operating mechanisms and producing a technique to enable the equipment to go from a stowed to an in-service position.

The substation also has built-in satellite and duplicate cellphone and fleetlink communication options to work from sites where communication networks aren’t available.

Transpower says the mobile substation provides a higher level of service to smaller communities that cannot afford the investment in duplicated transmission assets. It is also available for unforeseen events and improves safety during maintenance by reducing the time pressure on workers and providing them with greater flexibility.


Transpower used the two initiatives – demand response and deployment of the mobile substation – during a four-month programme at Tekapo earlier this year.

The closure of the Tekapo A & B power stations for maintenance meant that supply in the region was limited during periods of high summer demand.

Transpower used the shutdown to complete a seven-day upgrade and maintenance programme. Deploying the substation limited the loss of supply to eight hours, while the use of demand response helped the local lines company manage peak loads during the period.

The Innovation in Energy Award category is sponsored by Gentrack