Transpower has called a grid emergency and is working with electricity lines companies to manage controllable load such as hot water systems.

It follows a fault on the HVDC cable which transfers electricity from the South Island to the North Island. As a result, it is calling on consumers to be mindful of their electricity use this morning.

Some power is still flowing across the cable but a second fault could suddenly stop the flow of electricity. The System Operator is proactively managing this risk to prevent the risk of cascade grid failure if that second fault were to happen.

Transpower General Manager Operations Dr Stephen Jay said that the System Operator is working electricity lines companies and large industrial customers connected directly to the grid to reduce demand.

He said that at this stage New Zealanders would not notice any impact as lines companies would largely be turning off controllable load like hot water systems. Hot water systems are switched on and off regularly during winter.

Dr Jay said that if the removal of controllable load was not enough to balance the power system, then Transpower will need to ask for additional demand to be cut until the power grid is secure, which may result in some consumers being disconnected.

“We ask New Zealanders to be mindful of their electricity use this morning to help us get through this situation and avoid power cuts,” he said.

Some examples of how you can help are:

• Delay putting on a load of washing, using the dryer or dishwasher

• Delay charging electronic devices and electric vehicles

• Turn off heaters and lights in rooms that you are not using

“It is an unseasonable cold day so please stay warm by continuing to heat the rooms you are using, but consider turning down the thermostat a degree or two.”

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.

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