Grid stability |
What real grid events reveal about modern power system vulnerabilities
As recent events in the Iberian peninsula have shown, there remains a persistent gap between how power systems are planned and studied, and how they actually operate during disturbances. Understanding why this gap exists — and how to address it — is critical for grid security as the energy system transitions
Aditya Upadhye*
On 28 April 2025, it took just 27 seconds for the Iberian peninsula’s electrical system to collapse, leaving millions without power. At 12:32:57 CET, generation trips totalling approximately 2200 MW began in southern Spain. By 12:33:24 CET, the system had completely collapsed. The Spanish government report [1] and ENTSO-E Expert Panel investigation [2] found that voltage instability had been building throughout the morning, and that when the critical moment arrived, some generator disconnections occurred before voltage thresholds set by regulations had been exceeded. Whilst the official reports detail protection relay settings, frequency deviations, and system recovery timelines, they rarely capture a more fundamental challenge: the persistent gap between how power systems are expected to respond to disturbances and how they actually perform — and why this gap continues to surprise the industry. In this article, we will explore the existing challenges and the practical steps we can take to address them.
When regulation lags technology Three fundamental factors drive the widening gap between power system evolution and regulatory frameworks:
System complexity is outpacing our analytical approaches. Twenty years ago, grid disturbance analysis focused on a limited number of large synchronous generators with well-understood dynamic characteristics. Contemporary systems comprise thousands of distributed inverter- based resources, each with distinct control algorithms and response characteristics. The wide range of meteorological conditions, evolving load patterns (electric vehicles, data centres), and diverse market strategies deployed by participants significantly increase the complexities of operating bulk power systems in a stable and secure manner. Generator behaviour is becoming increasingly software defined. Modern power systems operate with reduced margins for error,
At point of connection
100 99 98 97 96
Active power phase total average (MW)
09:35:25 09:35:30 09:35:35 09:35:40 09:35:45 09:35:50 09:35:55 09:36:00 Date and time
-25 -30 -35 -40 -45 -50
Reactive power phase total average (MVAr)
09:35:25 09:35:30 09:35:35 09:35:40 09:35:45 09:35:50 09:35:55 09:36:00 Date and time
235 230 225 220 215 210
RMS phase V12 average (kV) RMS phase V23 average (kV) RMS phase V31 average (kV)
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Figure 1. Wind farm response during circuit breaker recloser operation. Source: VeriConneX
requiring every generator to perform precisely to specification. However, generator behaviour is now increasingly determined by software and firmware rather than only by physical characteristics. Software-defined generation can be reconfigured with a firmware update,
potentially changing grid support capabilities in a flash. Many grid codes still lack provisions for verifying that these critical settings remain compliant months or years after commissioning. The pace of deployment exceeds the pace of learning. Each generation of technology arrives
* Aditya Upadhye is managing director of VeriConneX and a director at GridWise Energy Solutions. He has over 20 years of power systems engineering the development of the COMET platform, Australia’s leading generator compliance monitoring solution, with over 2.5 GW of assets under management.
20 | November/December 2025|
www.modernpowersystems.com
Voltage (kV)
Reactive power (MVAr)
Active power (MW)
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