ImageOn January 15, 2013, I presented a webcast on Energy Central titled, “Geomagnetic Disturbances and their Impacts on Power Transformers”. You can view the presentation here.

The presentation generated many questions from the audience that I did not have time to address. This blog post addresses a few of those questions. Stay tuned for more posts with more questions and answers.

Question: Some people are claiming that a Geomagnetic Disturbances (GMD) event can result in large scale transformer failures. From a manufacturer’s point of view, what is, realistically, the magnitude of the risk of large-scale transformer failure

Answer: The literature cites a few cases where transformer thermal damage has been attributed to Geomagnetically Induced Currents (GIC). These cases indicate that the transformers in question were removed from service after the GMD event.

However, no forced outage or failure of a transformer due to GIC current has occurred during a GMD event is known. Given this, a large scale transformer failure involving multiple units would require a storm of cataclysmic proportions and one where the duration of maximum GIC flow was unprecedented.  NOAA is currently developing a "1-in-100 year" storm scenario, which indicates that such a monumental storm is extremely unlikely.

Question: Aside from harmonics, are there effects of GIC on 3-phase current and voltage waveforms that would be visible through CTs or VTs?

Answer: In addition to harmonic distortion, waveform magnitude may be reduced due to increased var demands from GIC-caused transformer saturation.  If additional system var support is not added in anticipation of major GMD events, this lack is expected to lead to system voltage collapse.

Question: Were any lives lost during the Quebec 1989 event?  How much property and commercial loss?

Answer: Technical literature references equipment damage to the electric system. More complete information about the outage can be found in "HQ System Blackout of March 13, 1989:  System Response to Geomagnetic Disturbance", presented at EPRI Conference on GIC, November 8, 1989, San Francisco, California.

Question: Are there events outside North America that can be used for study and analysis and lessons?

Answer: Nordic GMD experience is extensive, due to high Northern latitudes. See 2012 report by Lund University, ("Risk Analysis of Geomagnetically Induced Currents in Power Systems", pg. 15 and Appendix) for a complete discussion. In particular, the Halloween storm of October 2003 had a localized Swedish 130 kV outage due to harmonics and relay mis-operation. Stefan Arnborg, Swedish National Grid (SNG) reported at the 2012 EISS Summit "no equipment damage reported during more than 60 years of GMD monitoring, negligible GMD cost experienced and for severe GMDs, SNG anticipates voltage collapse without equipment damage."