SER vs FR vs DDR

SER vs. FR vs. DDR: The Event Data Your IBR Program Actually Needs (PRC-028-1 + ERCOT NOGRR 255)

When an inverter blinks, the grid notices. The difference between a clean audit trail and a week of guesswork comes down to three recordings: SER, FR, and DDR. Think of them as the plant’s timeline, high-speed replay, and fitness tracker. Used together, they explain what happened, why it happened, and how your system settled afterward—exactly what NERC PRC-028-1 and ERCOT’s NOGRR 255 are pushing toward.

Three recordings, three questions

• SER (Sequence of Events Recording): The time-stamped log of breaker operations, trips, alarms, and logic states.
  
  Question answered: What operated—and in what order?
  
  
• FR (Fault Recording): High-speed analog waveforms and digital bits captured around a trigger (shared as COMTRADE in most cases).
  
  Question answered: What happened electrically—in detail?
  
  
• DDR (Dynamic Disturbance Recording): Continuous or near-continuous measurements at synchrophasor rates to show plant and system behavior during and after a disturbance.
  
  Question answered: How did the plant and grid respond over time?
  

Together, these datasets connect event data analysis, IBR modeling, and NERC compliance automation in one loop.

What PRC-028-1 actually asks for (in plain English)

PRC-028-1 is the IBR-focused disturbance data rule for Generator Owners. The essentials:

SER (R1)

• Breaker status at the main power transformer (MPT) high side, collector bus breakers, and shunt reactive devices.
  
  
• For new IBR units, capture unit-level states on disturbance: fault codes, fault alarms, and ride-through mode status (voltage and frequency). Legacy units: “if capable.”
  

FR (R2–R3)

• Measure at the MPT high side, collector feeder breakers, and shunt dynamic reactive devices.
  
  
• Record V, I (including residual/neutral), and 3-phase P/Q where specified.
  
  
• Minimum quality: ≥64 samples/cycle, ≥2 cycles pre-trigger, ≥2.0 s total per record, with triggers for residual current and voltage/frequency excursions.
  

DDR (R4–R5)

• Continuous channels at the MPT: one phase-to-neutral (or positive-sequence) voltage, matching current (or positive-sequence), 3-phase P/Q, and frequency.
  
  
• Performance: input ≥960 samples/second, output ≥60 samples/second.
  

Time sync, formats, and delivery (R6–R8)

• Synchronize to UTC: ±1 ms for most devices, ±100 ms at the IBR-unit level.
  
  
• Retrievability: keep at least 20 calendar days of data accessible.
  
  
• Delivery: provide within 15 calendar days of request.
  
  
• Formats: SER in CSV; FR/DDR in CSV or COMTRADE; file names follow COMNAME.
  
  
• Outages: restore recording within ≤90 days, or file and execute a corrective plan.
  

Quick note for ERCOT teams: what NOGRR 255 changes

ERCOT’s NOGRR 255 raises the floor on time synchronization and recording performance for IBR facilities:

• Clocking: engineer to microsecond-class UTC accuracy across SER/FR/PMU devices.
  
  
• Continuous data: provide PMU-quality synchrophasors (~60 frames/second with ≥960 sps inputs).
  
  
• Fault recording: standardize ≥64 samples/cycle for new/updated devices and apply explicit triggers (undervoltage/overvoltage, frequency, residual currents, ROCOF).
  
  
• Data logistics: stage a rolling 20-day store and be prepared for fast turnaround on ERCOT requests.
  

Net effect: PRC-028-1 and NOGRR 255 aim for the same outcome—auditable, high-resolution evidence of IBR behavior—with ERCOT layering on tighter clocks and PMU-grade streams.

The “minimum viable” setup for an IBR plant

• Where to instrument
  
  
  • POI / MPT high side: FR + DDR; SER on breakers
    
    
  • Collector feeders: FR at feeder breakers; SER for operations
    
    
  • Shunt dynamic reactive devices: FR for V/I and reactive power; SER for steps/trips
    
    
  • IBR units: SER for fault codes, alarms, and ride-through modes on event
    
    
• How to configure
  
  
  • Triggers: residual/neutral overcurrent, over/undervoltage, over/underfrequency, plus IBR trip/ride-through flags into SER
    
    
  • Rates: FR ≥64 s/cycle; DDR/PMU ≥960 sps input and ~60 fps output
    
    
  • Time sync: GPS/IRIG-B/IEEE-1588 to meet PRC-028-1 tolerances—and microsecond-class for ERCOT sites
    
    
  • File discipline: CSV for SER; COMTRADE or CSV for FR/DDR; COMNAME naming; keep 20 days online
    

Pitfalls that derail audits (and how to prevent them)

• Clocks that don’t agree: implement monitored time-sync with alarms; document accuracy by device class.
  
  
• FR records too short or too slow: set and verify 64 s/cycle and ≥2.0 s per record with ≥2 cycles pre-trigger.
  
  
• No IBR-unit SER signals: map fault codes/alarms/ride-through modes into SER on disturbance.
  
  
• Inconsistent formats and filenames: standardize CSV/COMTRADE outputs and COMNAME naming to speed reviews.
  

Why this matters for modeling and verification

• FR reveals ride-through and current-limit behavior at sub-cycle resolution.
  
  
• DDR/PMU shows plant and grid dynamics for model benchmarking (e.g., PSCAD/PSS®E).
  
  
• SER ties actions and protections to the measured response.
  
  Combined, they create the evidence loop needed for IBR modeling, event data analysis, and a modern compliance platform.
  

How GridStrong makes it routine

• Pre-built templates for PRC-028-1 and NOGRR 255—rates, channels, triggers, time-sync, and COMNAME naming baked in.
  
  
• Unified ingestion of SER/FR/DDR/PMU with automated UTC alignment and format validation.
  
  
• Event-to-model loop: compare FR/DDR against plant models, flag mismatches, log corrective actions, and update compliance artifacts.
  
  
• Retrieval on demand: keep 20-day stores online and generate submission-ready bundles for ERCOT, TP/PC/TO/BA/RC/RE/NERC.
  

Talk to an Expert to operationalize SER/FR/DDR for PRC-028-1 and NOGRR 255—and connect event data to model validation with GridStrong’s compliance platform.