ERCOT’s GMD Vulnerability Assessment Requirements: How to Respond

On February 21, 2025, ERCOT issued a directive requiring all Transmission Service Providers (TSPs) and Resource Entities with points of interconnection (POIs) above 60 kV to conduct a Geomagnetic Disturbance (GMD) Vulnerability Assessment. This initiative represents a critical step in enhancing grid resilience against solar-induced phenomena that, while infrequent, can have widespread and severe impacts on transmission systems. 

GMDs occur when charged particles from solar flares interact with the Earth’s magnetic field, inducing electric fields across the ground. These geoelectric fields can create geomagnetically induced currents (GICs) in large-scale conductive infrastructure, including high-voltage transmission lines and transformers. GICs introduce quasi-direct currents into the AC grid, which can cause abnormal transformer operation, voltage instability, and most critically, malfunction of protection and control systems. 

ERCOT’s assessment is designed to proactively identify system elements – transformers, shunt devices, and lines – that could be inadvertently disconnected due to protection operations during GMD events. The study requires location-specific analysis of GIC susceptibility, considering factors such as conductor orientation, line length, grounding configuration, and regional geomagnetic profiles. 

We are actively supporting utilities and developers across ERCOT with GMD vulnerability studies. Our approach includes: 

• Site-Specific GIC Calculations: Using ERCOT’s provided steady-state cases and regional geophysical data, we model GIC flow across each identified asset. 
• Protection System Review: We analyze existing relays, protection schemes, and operational settings to evaluate the risk of disconnection under both Benchmark and Supplemental GMD scenarios. 
• ERCOT RFI Template Compliance: We complete and submit the required documentation for Category A/B events in line with ERCOT’s specifications. 

With a compliance deadline of May 31, 2025, time is of the essence. We provide deep expertise in electromagnetic disturbance assessments and protection system modeling. If your team needs support, we are ready to help you meet the ERCOT requirements with confidence and technical rigor. 

Let’s protect the grid – together. 

Meet with our experts

Schedule time online using Microsoft Bookings. Click here to schedule 30-minutes with our experts.