Working Group C4.32 “Understanding of geomagnetic storm environment for high voltage power grids”.

Technical boffins throughout CIGRE Australia are probably aware that the Solar Orbiter spacecraft successfully launched on Sunday 9 February from Cape Canaveral in Florida.  The mission goal is to study our closest star up close, particularly over the Polar Regions, so that we can better understand the physics, which drives the sun’s sometimes-temperamental behaviour.  One intended outcome of the research is to improve modelling and prediction of ‘space weather’ which is likely to deliver positive outcomes for earth’s communication and power systems.  Relevance to CIGRE you might ask? After several years of effort, CIGRE Working Group C4.32 has just published its Technical Brochure 780, which is titled “Understanding of geomagnetic storm environment for high voltage power grids” and which highlights the significant risks these events can place on power systems.  Dr William Radasky from the United States convened the WG, which included Australian members Robert Adams and Andrew Halley (who has produced this article).  This article also refers to an Australian paper to be presented at the CIGRE 2020 Paris Session entitled, “Monitoring and Modelling of Geomagnetically Induced Currents Across the Australian National Electricity Market”. 

The Technical Brochure (TB) covers a broad range of material, including the basic physics of geomagnetic disturbances (GMD), the sun’s solar cycle, how geomagnetically induced currents (GIC) occur and their impacts on power system equipment, the types of magnetic field disturbances that can occur, prediction of storm events, modelling and measurement of GIC, and mitigation options to lessen potential impacts on equipment and power systems more generally.  Large storm events from 1989 onward have been reviewed and available data analysed to provide practical examples of the various analysis and measurement concepts presented within the TB.

For those not familiar with GMDs and the resulting impacts, the main risks stem from the potential saturation of large power transformers which can lead to overheating and the injection of significant harmonics into the network.  Excessive hot spot temperatures can damage transformers which are expensive, long lead time items.  Additional reactive power consumption can reduce voltage controllability and in the extreme case, contribute to an increased risk of voltage collapse.  Elevated harmonics can cause spurious operation of protection relays, which can further weaken already stressed networks by incorrectly disconnecting ‘healthy’ equipment.

Examples of the above are discussed in the TB including the solar storm of 13 March 1989, which resulted in a blackout of the power system in Quebec, Canada.  While Australia has generally been considered less vulnerable, equipment damage has been reported from New Zealand and South Africa.  It is therefore prudent for all power system operators to understand the level of risk within their network and develop appropriate countermeasures for deployment when (and if) necessary.

The contents of the TB will hopefully prove to be a useful reference for not only power system operators, including generation and transmission businesses, but also equipment manufacturers, academia and any other institutions tasked with assessing the significance of GMDs and the implications of expected GICs when storm events are forecast.

The impacts of space weather from an Australian context have been further examined in a C4 paper recently submitted to the Paris 2020 Session.  Paper C4-114, which was led by Greg Hesse from Powerlink and contributed to by a number of other key organisations, is titled “Monitoring and Modelling of Geomagnetically Induced Currents Across the Australian National Electricity Market”.  The paper provides an excellent summary of efforts to measure and simulate GICs across the eastern seaboard of Australia, including Tasmania, and presents results coming from analysis of several solar storm events occurring from 2003 to 2015.  While the modelling to date has demonstrated good correlation between measured and simulated GICs, some significant differences in predicted GIC magnitudes are still to be resolved.  For those interested, the paper will become available later in 2020 as part of the Paris Session.

So next time you are fortunate enough to see the Aurora Australis in the southern skies, or are even more fortunate to be in the northern hemisphere to see the Aurora Borealis, stop and think about what might be going in the power system at the same time!  The side effects are very real and continue to be a very interesting consideration for our industry, even in Australia.

The TB is free for members and 270€ for non-members and can be DOWNLOADED from e-cigre HERE