May 28, 2025|News

Reassessing TOV Risk: Why Developers Can’t Ignore the Hidden Impact of NOGRR-245

By Kevin Chen

As renewable penetration accelerates and inverter-based resources (IBRs) become foundational to grid operations, evolving interconnection standards are forcing developers to revisit long-standing design assumptions. Updates such as ERCOT’s NOGRR-245 and IEEE 2800 are redefining fault ride-through (FRT) expectations by requiring IBRs to remain connected for longer periods of time during abnormal grid conditions. While these extended ride-through windows enhance overall system stability, they also introduce a critical and often overlooked vulnerability: increased exposure to Temporary Overvoltage (TOV) conditions.

Unlike transient lightning surges, TOVs are sustained voltage rises triggered by events such as ground faults, load rejections, or switching operations. As IBRs remain online during these disturbances, they can inadvertently extend the duration of elevated voltage conditions. Surge arresters – designed to absorb brief overvoltage events – are now being subjected to prolonged energy absorption, leading to thermal stress, premature aging, and increased risk of failure. These issues are no longer theoretical; they are emerging in real-world projects.

The push for longer FRT durations is fundamentally reshaping protection coordination. While inverters may be built to withstand prolonged overvoltages, associated equipment often is not.

The industry can’t afford to treat surge protection as a static calculation. With FRT windows stretching beyond previous norms, updated TOV studies are no longer optional — they're essential. Without them, developers risk underestimating stress on key equipment, compromising both reliability and project bankability.

At EPE, we help clients navigate these emerging risks. Our TOV restudy services provide the technical foundation to optimize protection coordination, extend equipment life, and ensure regulatory alignment.

As IBR developers adapt to new grid codes, now is the time to ask: Is your system truly prepared for what NOGRR-245 demands? Even if you think it might be, contact a member of our team below to help ensure your project’s compliance.

Related Intelligence

About the Author

Kevin Chen

Kevin Chen serves as EPE’s Head of Advisory Services. For more than a decade, he has been instrumental in the planning and design of over 2 GWs of power plant generation capacity, encompassing development, estimation, pre-construction, engineering and design, construction, and post-energization phases. Recognized for delivering independent engineering solutions, Kevin specializes in steady-state designs and dynamic studies for wind farms, centralized and distributed solar stations, DC/AC coupled and stand-alone Battery Energy Storage Systems (BESS), and data centers.

He brings extensive expertise in areas such as collection system design, North American Electric Reliability Corporation (NERC) compliance studies, interconnection feasibility studies, Development Engineering, EPC specification development, technical due diligence, project finance, and solar production estimates. With more than four years in leadership roles at EPE, Kevin is a technical authority in Independent Engineering Services in Energy Projects.

Kevin is a Licensed Professional Engineer in California and Texas. He holds a Doctor of Philosophy in Electrical Engineering from the Colorado School of Mines, a Master of Business Administration from Johns Hopkins University, and a Master in Public Administration specializing in Infrastructure and Energy from the Harvard Kennedy School.

We're here to help.

When you partner with EPE, you get an experienced team dedicated to providing you with tailored solutions and expert guidance.

Please fill out the form to the right, and a member of our team will be in touch.

The push for longer FRT durations is fundamentally reshaping protection coordination. While inverters may be built to withstand prolonged overvoltages, associated equipment often is not.