Just a few days ago, a reliable but anonymous source shared with me telemetry data from the day of the blackout, covering thousands of solar inverters deployed across Spain. Yesterday evening, the Spanish government released its official report on the blackout. In this post I present a detailed analysis of the telemetry data to understand how inverter-based resources may be linked to the voltage oscillations. This analysis offers a cyber-physical perspective that has not yet been publicly explored, and remains under investigation, according to the official report (p. 84-87) I would like to mention that yesterday morning, many hours before the official report was published, I informed INCIBE of my intention to publish this research. I believe this heads-up was the right thing to do. Watch out, a long read ahead. Introduction The following summary may be helpful for those looking to catch up on this complex scenario. Week 1 : Introduction to the Spanish transmission ne...