The S-PRO 4000 relay provides real-time processing of voltage and current signals with sub-harmonic monitoring at 1 Hz intervals between 5 Hz and 25 Hz (5 Hz, 6 Hz, 7 Hz… 23 Hz, 24 Hz and 25 Hz). It protects the grid from sub-harmonic oscillations at the point-of-common-coupling every one second, with additional user-configurable delays. Like all ERLPhase relays, the S-PRO is easy-to-use with intuitive settings and analysis software.
"The S-PRO was installed at a wind farm substation in Trimont, Minnesota, to detect sub-harmonic oscillations occurring at adjacent wind farms connected to the series compensated line," said Pratap Mysore, consulting engineer at Xcel Energy. "In tests so far, the unit has performed well and the relay has been designed well to detect and protect against sustained harmonics from the wind turbines."