Stop guessing what happens when your IBR trips

Are you certain your wind or solar farm is ready for the grid’s next major disturbance? The power system is changing fast, and inverter-based resources (IBRs) — solar, wind, and battery storage — are now front and center.

Events like the 2016 Blue Cut Fire disturbance in California, when a transmission fault led to the loss of roughly 1,200 MW of solar output, showed how little visibility the industry had into why IBRs trip. PRC-028-1, Disturbance Monitoring and Reporting Requirements for Inverter-Based Resources, is NERC’s answer. It took effect on April 1, 2025, and it requires Generator Owners to record what their IBR facilities do during a disturbance — and to hand that data over when asked.

Three kinds of data

The standard requires high-resolution data from critical points in the plant, such as the main power transformer and the collector feeder breakers. It asks for three distinct data sets, each answering a different question about an event:

  • Sequence of events recording (SER) — the security-camera footage. A time-stamped log of what opened and closed, and when, for the breakers associated with the main power transformer, collector buses, and reactive devices.
  • Fault recording (FR) — the triggered snapshot. When an event hits, voltage and current waveforms are captured at the high side of the main power transformer and on the collector feeder breakers, at a minimum of 64 samples per cycle.
  • Dynamic disturbance recording (DDR) — the system’s EKG. Continuous recording at each main power transformer, at least 60 times per second, to capture power swings and oscillations.

All three have to be time-synchronized to UTC: within ±1 millisecond for substation devices, and within ±100 milliseconds for the IBR units themselves. Without a common timebase, the records can’t be lined up against each other or against the rest of the grid.

When someone asks for the data

Recording isn’t enough. Your Transmission Operator, Reliability Coordinator, Planning Coordinator, Regional Entity, or NERC can request the data at any time. It must be retrievable for 20 calendar days after it was recorded, and it must be delivered within 15 calendar days of the request — SER as CSV, and fault records as CSV or COMTRADE. Without the data, a single event can become a compliance violation.

The countdown

For BES IBRs already in commercial operation, compliance phases in. Requirements R1 through R7 apply to 50% of a Generator Owner’s existing BES IBRs within three calendar years of the effective date — Texas RE puts that at December 31, 2028 — and to 100% by January 1, 2030. Facilities that enter commercial operation after the effective date have to comply from the start.

That sounds like plenty of time. It usually isn’t. For a typical utility-scale solar farm or battery energy storage system, full compliance means an engineering retrofit: new or reconfigured hardware, a communications architecture that can move the data, and coordination with the SCADA and protection systems already in place. Those projects need procurement, outages, and testing — and every Generator Owner is working against the same dates.

Centralizing the data with an RTAC

The good news: most sites already have intelligent electronic devices — relays and meters — that can produce much of this data. The challenge is centralizing it, time-synchronizing it, and turning it into one cohesive, compliant record you can deliver on request.

That’s where a substation automation controller such as the SEL-3555 Real-Time Automation Controller (RTAC) earns its place:

  • One place for the data. The RTAC aggregates records from the site’s relays and meters into one system, instead of leaving them scattered across a dozen devices.
  • A common clock. Paired with a satellite-synchronized clock, it keeps every record on the same UTC timebase.
  • Audit-ready output. It handles the data management, so when a request arrives the records can be pulled and delivered well inside the 15-day window.

The right architecture depends on what’s already installed. Some sites need little more than configuration and communications work; others need new recording devices. Either way, it pays to know which long before the deadline.

Start with an assessment

An ounce of prevention is worth a pound of cure. We help Generator Owners assess existing IBR sites against PRC-028-1 — what’s recorded today, what’s missing, and what it will take to close the gap — and then design, program, and commission the solution.

Sources: NERC PRC-028-1 · NERC implementation plan · Texas RE on PRC-028-1 compliance dates