Tva Response To Geomagnetic Storm May 10-13, 2024
In order to better understand the power system impacts of geomagnetic disturbances (GMD), the Tennessee Valley Authority (TVA) has developed a network of monitors in cooperation with the Electric Power Research Institute (EPRI). The network includes devices to measure geomagnetically induced current (GIC) in the neutrals of several 500kV power transformers, along with a network of twelve magnetometers geographically dispersed around the TVA system.
TVA made use of the data provided by these devices during the GMD events of May 10-13, 2024.
The Space Weather Prediction Center began issuing alerts for a significant geomagnetic disturbance on the morning of May 10, 2024. TVA began noticing effects 5/10/2024 at about 10:00AM system time (15:00UTC), and began accessing data from all available devices.
The highest GICs measured were over 40Adc (compared against an action threshold of 225Adc).
TVA also monitored for system harmonics, but noted only a slight increase in system harmonics.
No equipment issues were reported or observed. No capacitor banks tripped due to harmonics. There were no observed increases in the reactive losses in any power transformer.
Besides monitoring, TVA also has partnered with EPRI to install a neutral blocking device (NBD) at a substation located in the northwest corner of the TVA system. The device is connected in the 500kV neutral of the three-phase power transformer at that station and consists of a capacitor that is normally bypassed. The control for this device inserts a capacitor in the neutral if the measured DC current is greater than 5 amperes is measured for longer than five seconds. The control will bypass the capacitor after measuring less than 5 volts DC across the capacitor for longer than one hour. TVA performed studies to evaluate the impact of the device should a ground fault occur near the station when the capacitor is in service (capacitively grounded neutral).
For this GMD, the NBD inserted 12 times from 5/10/2024@12:05 system time to 5/12/2024@23:39 system time. Longest insertion time was a little over 2 hours (5/10/2024 from 13:58:21 to 16:00:39 system time). TVA evaluated the GIC measured at adjacent and nearby transmission sites during the times the NBD was in-service and determined the effects were minimal.