figure 8. Swissgrid's public web page. One Day * 100% 0.01 0.5 Hz 50.2 50% 0.005 0.25 Hz 50 0% 0 0 Hz 49.8 18:00 1/6/2015 00:00 1/7/2015 06:00 12:00 figure 9. Power oscillation monitoring and modal analysis output (damping: green; frequency: brown; oscillation frequency: blue; and oscillation amplitude: yellow). 46 ieee power & energy magazine september/october 2015