This joint New Zealand-United Kingdom project aims to investigate the risk posed by Geomagnetically Induced Currents (GIC) to New Zealand’s South Island electrical transmission network. GIC in New Zealand’s electrical network are caused by space weather storms. During very large space weather storms GIC can cause significant damage to electrical transformers. As an example, after the event of 6 November 2001 a Dunedin transformer was written off due to the impact of a large storm that caused multiple alarms across Transpower’s South Island network.
In this talk we will present analysis of Transpower New Zealand Ltd’s 17 years of GIC measurements made at up to 62 transformers. We have found a strong correlation between the GIC magnitude and the rate of change of the horizontal component of the magnetic field at Eyrewell, as expected from theory.
We will also present our model to calculate GIC in the South Island. Our goal for the model is to explore the impact of extreme space weather storms and to evaluate mitigation protocols to reduce these impacts. New Zealand’s geomagnetic latitude and island setting mean that we are able to use modelling approaches which have been successfully applied in the past for the United Kingdom. Going beyond the substation level models that have been used previously, we have included every transformer within each substation in our South Island network model. The model and observations show strong spatial variation in GIC, even within substations. As we will validate our model against the extensive Transpower observations, this will be a valuable confirmation of the modelling approaches used by the wider international community as well as contributing to the security of New Zealand’s power supply.