As a result of a fault on the HVDC system which transfers electricity from the South Island to the North Island this
morning Transpower called a grid emergency.
The grid emergency allowed the System Operator to work with lines companies to remove controllable load like hot water
systems until the fault was able to be resolved. Hot water systems are switched on and off regularly during winter and
New Zealanders will not have noticed any impact.
Transpower CEO Alison Andrew said that Transpower worked quickly to maintain system security during the grid emergency.
“We have a grid emergency system in place for exactly this type of situation,” Ms Andrew said.
“Lines companies knew what was expected of them and they moved quickly to manage controllable load and reduce demand. No
consumers were disconnected and the system stayed stable throughout.”
She thanked New Zealanders who had taken action to be mindful of their power usage. “Fortunately we were able to resolve
the issue before we had to cut additional demand which would have resulted in some consumers being disconnected. We are
grateful to those New Zealanders who took action to reduce their usage.”
The HVDC is now fully operational and there is plenty of power available for the North Island.
Background
Transpower’s role
Transpower, as the electricity System Operator, is responsible for managing the real-time power system and operating the
wholesale electricity market. Transpower does not own or operate any electricity generation.
Hot water ripple control
Traditional hot water cylinders around the country have separate meters which allow local electricity lines companies to
turn them on and off. An average hot water cylinder contains approximately one day’s hot water usage and needs
approximately 3-4 hours of heating per day to recharge. This means if it is turned off for a short period you are
unlikely to see any impact on your hot water supply.
Every winter electricity lines company use hot water ripple control to manage load on the network to ensure it is not
overloaded, during network issues and during maintenance.