Historical Geomagnetic Disturbances and their Protection System Impacts

Several storms have caused adverse impacts on power systems due to high GIC levels. A review of the literature reveals numerous GMD events that have caused protection system trips that removed equipment from service or caused a loss of load since 1981. Not all the reports provided detailed causes of the relay trips but several events that have been reported with greater detail will be examined in depth. A higher level summary table can be found after this section.

1980 and 1981 Geomagnetic Storms

On the Minnesota Power system, a 500 kV line interconnected to Manitoba built in 1980 had three operations of the time-overcurrent protection scheme during its first year of operation. This was due to GIC induced harmonics caused the relay to operate on the negative and zero sequence currents due to harmonic distortion. The time backup sensitive ground fault relay misoperated on third harmonic currents. About 200 Amps of zero sequence current was seen on the third harmonic and 100 Amps of negative sequence current was seen on the fifth harmonic. The positive sequence line current also showed both a fundamental component and significant fourth harmonic distortion [1].

On the B.C. Hydro system, a 500 kV line tripped in April and May of 1981 due to an overcurrent relay operating because of even order harmonic distortion caused by GICs. The relay was designed to detect negative sequence current, and testing showed that higher harmonics could cause the relay to operate [1].

March 1989 Geomagnetic Storm

On March 13th, a GMD event blacked out the Hydro-Quebec system in Quebec, Canada. Second and fourth order harmonics currents generated by transformer half-cycle saturation caused the trip of numerous static var compensators (SVC) that ultimately led to the collapse of the Hydro-Quebec system. The SVCs all failed before operator action could be taken. They were followed by the loss of a 735 kV line leading to the loss of generation and further equipment [2].

At La Verendrye, there was significant second (16.7%) and fourth (4.6%) order harmonics due to transformer saturation which caused the SVC overvoltage protection to trip.

At Nemiscau – Albanel, three SVCs tripped due to capacitor unbalance protection, and two SVCs tripped due to resistor overload protection devices of the third harmonic filter branch. Again, there was significant second and fourth order harmonic distortion. Additionally, voltage and current distortion was in excess of protection device settings.

The effects of the GMD storm were also felt much further south than Canada. Several capacitor banks neutral unbalanced protection schemes misoperated due to excessive harmonics in the Dominion Energy Virginia system. The relays protecting the capacitor banks could not distinguish between the fundamental and other harmonics [3].  In Maine, capacitor banks tripped due to neutral overvoltage protection schemes being triggered. Some additional reactive device tripped due to neutral overcurrent protection and neutral unbalance protection schemes [4].

Two lines also tripped during the event. The Manitoba Hydro Radisson-Churchill line tripped due on a 50N relay. A Western Area Power Administration line tripped due to negative sequence relay operation.

March 1991 Geomagnetic Storm

From March 22nd – 24th, a GMD event tripped static compensators in Pennsylvania due to neutral unbalance protection. A capacitor bank in New York tripped on its neutral overcurrent protection which used an induction disk overvoltage relay [4].

July 2000 Geomagnetic Storm

On July 15th, 2000, the Tennessee Valley Authority lost 6 capacitor banks on their 161 kV system totaling 800 MVAR of capability. The event was preceded by a geomagnetic storm and the resulting transformer half-cycle saturation caused simultaneous trips of the capacitors zero sequence voltage supervised residual overcurrent (GE SFC) relay across several hundred miles [5].

November 2001 Geomagnetic Storm

On November 6th, 2001, a GMD event caused an SVC in Christchurch, New Zealand to trip. The SVCs negative sequence overcurrent relay was tripped and there was noticeable second harmonic currents in the waveforms [6].

Halloween Geomagnetic Storm of 2003

On October 29th to 31st, 2003, a solar storm known as the Halloween storm caused numerous protection system misoperations across Sweden. Many of these relay misoperations were traced back to low set residual overcurrent relays for lines and transformers. Of the relays that operated, 50% were second harmonic restrained residual overcurrent relays. Some of the low set independent residual overcurrent relays tripped due to increased residual current because of harmonic distortion on underground cables.

In Malmö, an outage was caused by a low set residual overcurrent relay on the 130 kV system which was sensitive to third harmonics. The operating value at the third harmonic was 37% of the fundamental frequency. The cable network and bus voltage distortions increased the residual current which caused the relay to trip.

The Swedish system uses a system of three high-set independent time directional overcurrent relays to protect against for earth faults. The relay with highest setting operates immediately, while the others have 0.4s time delay. In 1986 all low set residual overcurrent relays were replaced by time dependent time overcurrent relays with logarithmic characteristics and second harmonic restraints on the 400 kV and 220 kV system. However, on the 130 kV system the relays were not upgraded [3].

September 2017 Geomagnetic Storm

On September 8th, 2017, a GMD event caused a differential relay on a 420 kV to 69 kV transformer to trip in Tromsö, Norway. Measurements showed significant distortion on the high voltage side phase currents with each phase having a noticeable offset. The second harmonic was at 30% and the fifth harmonic was at 10% of the fundamental current respectively. The relays restraint quantities were not enough to prevent misoperation of the transformer differential relay [8].

May 2024 Geomagnetic Storm

On May 10th to 11th, 2024 one of the strongest solar storms in decades caused harmonic distortion that was suspected of tripping of equipment on the grid, including a of a 110 kV line, 138 kV capacitor bank, and triggered voltage oscillations from a solar plant and battery bank [9].

Sources

[1]    D. H. Boteler, T. Watanabe, R. M. Shier, R. E. Horita, “Characteristics of Geomagnetically Induced Currents in the B. C. Hydro 500 kV System.” IEEE Transactions on Power Apparatus and Systems, Vol. PAS-101, no. 6, pp. 1447–1456, June 1982.

[2]    “NERC 1989 Quebec Disturbance Report.” Available: https://www.nerc.com/pa/Stand/Geomagnetic%20Disturbance%20Resources%20DL/NERC_1989-Quebec-Disturbance_Report.pdf.

[3]    R. Sun, M. McVey, M. Lamb, R. M. Gardner, “Mitigating Geomagnetic Disturbances – A summary of Dominion Virginia Powers efforts,” IEEE Electrification Magazine, vol. 3, no.4, pp. 34-45, Dec. 2015.

[4]    Working Group K-11 of the Substation Protection Subcommittee of the Power System Relaying Committee, “The Effects of GIC on Protective Relaying,” IEEE Transactions on Power Delivery, vol. 11, no. 2, pp. 725-739, April 1996.

[5]   R. W. Patterson. (2001, May). “Mathcad Analysis of Davidson Capacitor Bank Misoperation”, Presented at Georgia Tech 2001 Fault and Disturbance Analysis Conference. [Online]. Available: http://relayman.org/papers/2001fault_conf_paper.pdf

[6]   J. Béland, K. Small, “Space Weather Effects on Power Transmission Systems: The Cases of Hydro-Québec and Transpower New Zealand Ltd,” in Effects of Space Weather on Technology Infrastructure, vol. 2, no. 2. New York: Kluwer Academic Publishers, 2004, ch. 15, pp 287-299.

[7]  A. Pulkkinen, S. Lindahl, A. Viljanen, R. Pirjola, “Geomagnetic storm of 29–31 October 2003: Geomagnetically induced currents and their relation to problems in the Swedish high-voltage power transmission system,” Space Weather, vol 3, no. 8, Aug. 2005.

[8]  D. Bejmert,K. Boehme, M. Kereit, W. Rebizant, “HV Transformer Protection and Stabilization under Geomagnetically Induced Currents” Energies, vol. 13, no. 18, Sept. 2020.

[9] NERC “May 2024 Geomagnetic Disturbance Event Review.” NERC Staff Report, January 2026. Available: https://www.nerc.com/globalassets/programs/rapa/gmd/reference-documents/may-2024-gmd-event-review.pdf