State owned enterprise Transpower owns and operates New Zealand’s national electricity transmission system. The system includes substations, high voltage cables, transformers and overhead lines for transmitting high voltage electricity from power stations to distribution (lines) companies.
The electricity grid
New Zealand’s electricity grid is an AC transmission system, with a DC connection from the southern South Island at Benmore Station on the Waitaki River, across Cook Strait by undersea cable to the southern end of the North Island. This type of transmission is called a high voltage direct current (HVDC) system.
Transpower transmits most of New Zealand’s electrical energy using high capacity, high voltage transmission lines to regional distribution companies. It also supplies electricity directly to some large industrial companies.
Coordinating the grid
As the national grid’s System Operator, Transpower also provides a network coordination service. It schedules the generation of all power stations, monitors interconnected networks, ensures that reliability, voltage and frequency targets are met, and manages grid emergencies.
The Electricity Authority manages a service provider contract with Transpower to ensure effective grid management. As System Operator, Transpower is responsible for the real-time operation of the electricity system.
Under the Electricity Industry Act 2010, the System Operator is also required to provide information and provide forecasts on the security of supply, and to manage supply emergencies.