Session 7 - GICs: Ground system hazards from geomagnetically induced currents – research, developments, services, and operations.

Mark Clilverd (British Antarctic Survey, UK), Craig Rodger (Univ. of Otago, NZ)
Tuesday 19/11, 09:00-10:30
Elisabeth

Geomagnetically induced currents (GIC) in ground systems are one of the better recognised hazards that can result from large geomagnetic storms, appearing in many national risk registers. Coupling via processes in the ionosphere, an example of GIC is the hazard to electrical transmission networks as a consequence of damage to power network transformers at high, mid and even comparatively low geomagnetic latitudes. Another example of the hazard is through induced currents in long-distance pipeline structures, with changes in protective offset voltage biases and increased potential for corrosion. However, understanding the origin of the hazard, and providing alerts to operators is challenging, due to the complexity of the physical linkages involved. The measurement, modelling, prediction and mitigation of the effects of Space Weather on the ground, such as unwanted geomagnetically induced currents in power systems, pipelines, and railway networks are required by the industries affected.

In this session we particularly encourage submissions which identify end user requirements and experience, together with new developments in space weather operations or services including underpinning research, best practice in transitioning research to operations, and verification activities. We also would like to hear from those involved in developing early warning of ground-level geomagnetic disturbances from solar wind measurements, members of industry, and from those involved in the modelling of the magnetosphere during geomagnetic storms with a regard to understanding the processes involved in the generation of ground-level and near-Earth disturbances. We also welcome general contributions that advance GIC research and applications of research.

Talks
Tuesday November 19, 09:00 - 10:30, Elisabeth

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Talks : Time schedule

Tuesday November 19, 09:00 - 10:30, Elisabeth

09:00	Geomagnetically Induced Currents (GICs): The Role of Space Weather Services	Singer, H et al.	Invited Oral
	H.J. Singer[1], C. Balch[1], M. Cash[1], R. Steenburgh[1], W. Murtagh[1], G. Millward[2], E. Camporeale[2], G. Toth[3], and Z. Huang[3]
	1] NOAA Space Weather Prediction Center, [2] University of Colorado, Cooperative Institute for Research in Environmental Sciences (CIRES), [3] University of Michigan, Climate and Space Sciences and Engineering
	Since the Carrington event of 1859, it has been well-known that geomagnetically induced currents (GICs) on long-line conductors are a societal concern. In 1859, an extreme geomagnetic storm interfered with telegraph communications, while today, in modern times, the concern is mostly about electric power grids. Our society relies on the continuous and reliable availability of electric service for a multitude of interconnected services such as banking, refrigeration, health, water delivery, manufacturing, transportation and national security. For these reasons, it is essential that we are able to predict extreme geomagnetic disturbances, understand geomagnetic storm impacts on power grids, and other similar technologies, and be prepared to react to and recover from large geomagnetic storms. In this presentation, we will describe the history and motivation for providing space weather services for GIC conditions, including recent policy and planning in the United States related to the National Space Weather Strategy and Action Plan. We will describe the solar, geomagnetic and geoelectric observations and models, planned and in use, to support space weather affected customers, as well as the challenges for improving space weather services. Most importantly, we will discuss the “middleman” role of the space weather service provider, such as the NOAA’s Space Weather Prediction Center, and the benefits of our work as a link between the research community that develops new understanding and tools, and the end user, or power grid operator, that utilizes the provided services.
09:30	Modelling GICs in Sweden – verification and extreme event analysis	Rosenqvist, L et al.	Invited Oral
	Lisa Rosenqvist[1], Tim Fristedt[2], Andrew P. Dimmock[3], Daniel Welling[4], Maxim Smirnov[5], Emiliya Yordanova[3]
	[1] Swedish Research Defence Agency (FOI), [2] Multiconsult, [3] Swedish Institute of Space Physics, [4], University of Texas at Arlington, [5] Luleå Technical University
	A proof-of-concept modelling capability that incorporates a detailed 3-D structure of Earth’s electrical conductivity in a GIC estimation procedure has been developed (GIC-SMAP) and verified based on GIC measurements in northern Sweden. However, 3-D modelling show that southern Sweden is exposed to stronger electric fields due to a combined effect of a low crustal conductivity and the influence of the surrounding coast effect. Earlier studies have also shown that the Swedish power grid is especially vulnerable to GICs in the southern parts. This study utilizes GIC measurements conducted in collaboration with Svenska Kraftnät on a power line at the west coast of southern Sweden to verify the GIC-SMAP modelling framework in this region. After verification the model is used to quantify the hazard of severe GICs in this particular transmission line by applying historic recordings of strong geomagnetic disturbances to the GIC-SMAP modelling framework. To quantify a worst case scenario we also calculate the GIC based on modelled magnetic disturbances by the Space Weather Modelling Framework (SWMF) based on hypothetical extreme CME conditions. The current state-of-the art prediction capability of GICs is evaluated by comparing the GICs estimated based on observed magnetic disturbances during the St. Patrick storm in March 2015 to the predicted GIC based on modelled magnetic disturbances with SWMF. The key points are the following. The observed and estimated GIC based on the GIC-SMAP procedure in the transmission line in southern Sweden are in excellent agreement. The estimated GICs at the location of the transmission line during historical geomagnetic disturbances exceed 100 A only for one of the 13 storm intervals, however, it is highly dependent on the magnetic latitude of the observations. The maximum GIC during the storm commencement estimated based on a hypothetical extreme CME exceeds 400 A but depends highly on the MLT sector. Although SWMF does capture parts of the rapid, high magnitude localized magnetic disturbance over Scandinavia during the St. Patrick storm it underestimates the maximum GIC by more than a factor two for high latitudes.
10:00	Transpower measurements of GIC in New Zealand	Rodger, C et al.	Invited Oral
	Craig J. Rodger[1], Michael Dalzell[2],
	[1] University of Otago, Dunedin, New Zealand, [2] Transpower NZ Ltd, Wellington, New Zealand.
	Transpower New Zealand Limited is responsible for electric power transmission in New Zealand. They have archived near-continuous measurements of DC current in transformer neutrals in the New Zealand electrical network at multiple South Island locations for nearly two decades - providing a dataset including Geomagnetically Induced Currents (GIC). From 2001 onwards up to 58 individual transformers from up to 17 substations have been simultaneously monitored. In the last decade, there has been growing evidence of Geomagnetically Induced Current (GIC) impacts at low and mid-latitudes, including the United Kingdom, South Africa, New Zealand, Brazil, China, and Japan. Work undertaken in South Africa has demonstrated increased transformer problems after large geomagnetic storms resulting in transformer deterioration and eventual failure. The New Zealand Transpower measurements provide an unusually long and spatially detailed dataset of such GIC conditions. For example, at 1:52 UT on 6 November 2001 Transpower received alarms from its transformers spread across the South Island. Simultaneously voltage control equipment for Christchurch city tripped, along with a transformer partially feeding Dunedin city. A single-phase unit of the Dunedin city transformer failed within one minute of the GIC onset time and was subsequently written off. We will focus on the primary questions Transpower has asked Space Weather researchers which are needed to develop a business case to prepare for extreme geomagnetic storms. Our talk will also describe the operational aspects of monitoring the effects of geomagnetically induced currents in power systems including what to measure, how, and why. Operational mitigation options that could be implemented for large GIC events occurring in New Zealand will be discussed.

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