ERCOT (NOG 2.9.1) ride-through requirements
Low-voltage ride-through, High-voltage ride-through for the United States. Every breakpoint below is read from the code itself, and where a point was taken off a published figure rather than stated in the clause, the section under that chart says so — a breakpoint computed from the clause.
What is the low-voltage ride-through envelope for ERCOT (NOG 2.9.1)?
The plant must ride through for any voltage that stays on or above this envelope. The envelope holds 0 pu from t = 0 to 320 ms; then ramps linearly from 0.095625 pu at 320 ms to 0.25 pu at 594.444 ms; then 0.25 pu from 594.444 ms to 1.2 s; then 0.5 pu from 1.2 s to 3 s; then 0.7 pu from 3 s to 6 s; then 0.9 pu from 6 s onward — the last band the envelope defines, with no stated end time. Correction: the vertices plotted here are computed from the clause’s line rather than read from it, so these times and voltages appear in no clause.
The clause states this boundary as a line; the plotted breakpoints are computed from it, not read from it.
Applies to Transmission-connected IBRs: PVGRs and ESR IBRs (ERCOT)
| From | To | Voltage | Between the points |
|---|---|---|---|
| 0 | 320 ms | 0 pu | Held flat |
| 320 ms | 594.444 ms | 0.095625 → 0.25 pu | Ramps linearly |
| 594.444 ms | 1.2 s | 0.25 pu | Held flat |
| 1.2 s | 3 s | 0.5 pu | Held flat |
| 3 s | 6 s | 0.7 pu | Held flat |
| 6 s | no stated end | 0.9 pu | Held flat |
The clause this came from
ERCOT Nodal Operating Guides, Section 2.9.1.1 'Preferred Voltage Ride-Through Requirements for Transmission-Connected Inverter-Based Resources (IBRs)', paragraph (1), Table B: Applicable to PhotoVoltaic Generation Resources (PVGRs) and ESR IBRs, plus the following paragraph defining the sub-0.25 pu straight-line function ('0.15 seconds at zero voltage and 1.75 seconds at 0.9 p.u. voltage'). Source: February 1, 2026 ERCOT Nodal Operating Guide PDF (body dated DECEMBER 5, 2025), sheet pp. 52-54. The code defines a linear recovery ramp; the vertices are read from the clause and the chart draws the segment between them.
On this row that last sentence does not hold. The clause states the line; the vertices plotted here are its intersections with the staircase, computed rather than read, so treat those exact vertices as derived.
What is the high-voltage ride-through envelope for ERCOT (NOG 2.9.1)?
The plant must ride through for any voltage that stays on or below this envelope. The envelope holds 1.2 pu from t = 0 to 1 s; then 1.1 pu from 1 s onward — the last band the envelope defines, with no stated end time.
Every breakpoint is stated in the clause cited below.
Applies to Transmission-connected IBRs: PVGRs and ESR IBRs (ERCOT)
| From | To | Voltage | Between the points |
|---|---|---|---|
| 0 | 1 s | 1.2 pu | Held flat |
| 1 s | no stated end | 1.1 pu | Held flat |
The clause this came from
ERCOT Nodal Operating Guides Section 2.9.1(1)(a)/(b) (applicability by SGIA date, no MW threshold); Section 2.9.1.1(1) Tables A and B high-voltage rows (1.10<V<=1.20 -> 1.0 s; V>1.20 may ride-through or trip); Section 2.9.1.2(1) Table A (1.175<V<=1.2 -> 0.2 s; 1.15<V<=1.175 -> 0.5 s; 1.10<V<=1.15 -> 1.0 s). sheets pp. 50-55.
Operating requirements beyond the envelopes.
The envelopes above are what ERCOT (NOG 2.9.1) demands during a disturbance. The rows below are the same regime’s operating and fault-response requirements — reactive capability, frequency response, continuous operating range, ramp rate, RoCoF withstand and fault-current injection — each researched from the document its own row cites, separately from the plotted corpus. Every row carries its clause and a verbatim quote, so you can check it the same way.
| Requirement | What the code states | Clause |
|---|---|---|
| Voltage Support Service reactive capability (rectangular Q profile) Reactive capability | Power factor <= 0.95 over-excited (lagging) and <= 0.95 under-excited (leading), both determined at maximum net power and measured at the POIB; capability required at ALL MW levels (rectangle shape), and for ESRs when charging or discharging. Lagging capability applies for Voltage Set Points 0.95-1.04 pu; leading for 1.0-1.05 pu Binds all Generation Resources and Energy Storage Resources connected to Transmission Facilities with gross unit rating >20 MVA (or aggregating >20 MVA at the same Point of Interconnection Bus) that supply power to the ERCOT Transmission Grid; ESR charging-side exemption only for pre-16-Dec-2019 ESRs with an ERCOT-confirmed attestation. | Nodal Protocols Section 3.15, Voltage Support, paragraphs (2), (4)(a), (4)(b), (4)(e) |
The clause this row citesNodal Protocols Section 3.15, Voltage Support, paragraphs (2), (4)(a), (4)(b), (4)(e) — “ An over-excited (lagging or producing) power factor capability of 0.95 or less determined at the unit's maximum net power to be supplied to the ERCOT Transmission Grid and for any Voltage Set Point from 0.95 per unit to 1.04 per unit, as measured at the POIB; … An under-excited (leading or absorbing) power factor capability of 0.95 or less, determined at the unit's maximum net power to be supplied to the ERCOT Transmission Grid and for any Voltage Set Point from 1.0 per unit to 1.05 per unit, as measured at the POIB; … This Reactive Power profile is depicted graphically as a rectangle. … For ESRs, the Reactive Power capability shall be available at all MW levels, when charging or discharging, and may be met through a combination of the ESR's CURL, and/or dynamic VAr-capable devices. ” (ERCOT Nodal Protocols, accessed 2026-07-28) | ||
| Governor droop and deadband limits for ESRs (NOG) Frequency response | Droop <= 5% for ESRs (4% for combined-cycle combustion turbines); frequency deadband <= +/-0.017 Hz for ESRs and other non-mechanical-governor units (+/-0.034 Hz for steam/hydro turbines with mechanical governors; +/-0.036 Hz for Controllable Load Resources) Binds every Generation Resource and ESR connected to the ERCOT System — a Governor (frequency-responsive control) must be in service whenever connected (NOG 2.2.7(1)); steam turbines of combined-cycle plants, SOTGs and SOTSGs are excepted from the tables. The combined-cycle, mechanical-governor and Controllable Load Resource comparison figures are cited from the remaining rows of Tables 1 and 2 but are not carried in the quoted text. | Nodal Operating Guides Section 2.2.7, Turbine Speed Governors, paragraph (3), Table 1 and Table 2 |
The clause this row citesNodal Operating Guides Section 2.2.7, Turbine Speed Governors, paragraph (3), Table 1 and Table 2 — “ Generation Resources and ESRs, except steam turbines of Combined Cycle Generation Resources, Settlement Only Transmission Generators (SOTGs), and Settlement Only Transmission Self-Generators (SOTSGs) shall have Governor droop characteristics and Governor Dead-Band settings no greater than those shown below in Table 1, Maximum Governor Dead-Band Settings, and Table 2, Maximum Governor Droop Settings … All Other Generating Units/Generating Facilities/ESRs +/- 0.017 Hz … All Other Generating Units/Generating Facilities/ESRs/CLRs 5% ” (ERCOT Nodal Operating Guides, August 1, 2026, accessed 2026-08-10) | ||
| BAL-001-TRE-2 R6 governor settings (regional reliability standard) Frequency response | Governor deadband <= +/-0.017 Hz (all generating units/facilities except steam and hydro turbines with mechanical governors, which get +/-0.034 Hz); droop <= 5% (4% for combined-cycle combustion turbines) Binds each Generator Owner in the ERCOT Interconnection (NERC/Texas RE regional standard); Table 6.2 lists Variable Renewable (Non-Hydro) at 5% — ESRs are not named here, but ERCOT NOG 2.2.7 Tables 1-2 apply the same limits expressly to ESRs. The +/-0.034 Hz deadband for steam and hydro turbines with mechanical governors is cited from the remaining Table 6.1 row but is not carried in the quoted text. | BAL-001-TRE-2, Requirement R6, 6.1 Table 6.1 Governor Deadband Settings and 6.2 Table 6.2 Governor Droop Settings |
The clause this row citesBAL-001-TRE-2, Requirement R6, 6.1 Table 6.1 Governor Deadband Settings and 6.2 Table 6.2 Governor Droop Settings — “ Each Generator Owner shall set its Governor parameters as follows: 6.1. Limit Governor deadbands within those listed in Table 6.1, unless directed otherwise by the Balancing Authority. … All Other Generating Units/Generating Facilities* +/- 0.017 Hz … 6.2. Limit Governor droop settings such that they do not exceed those listed in Table 6.2 … Hydro 5% Combustion Turbine (Simple Cycle and Single-Shaft Combined Cycle) 5% Combustion Turbine (Combined Cycle) 4% Steam Turbine* 5% Diesel 5% DC Tie Providing Ancillary Services 5% Variable Renewable (Non-Hydro) 5% ” (BAL-001-TRE-2 — Primary Frequency Response in the ERCOT Region, accessed 2026-07-28) | ||
| PFR performance ratio and measurement windows Frequency response | >= 0.75 twelve-month rolling-average initial AND sustained Primary Frequency Response performance (actual/expected ratio); initial response measured 20-52 s after the Frequency Measurable Event starts, sustained response measured 46-60 s after t(0) BAL-001-TRE-2 R9/R10 bind each Generator Owner per generating unit/facility based on participation in at least eight FMEs; ERCOT NOG 2.2.8(1) applies the identical 0.75 initial and sustained requirement expressly to ESRs (with charge/discharge headroom exclusions). | BAL-001-TRE-2, Requirements R9 and R10 and Section A, Introduction, 6. Background; see also Nodal Operating Guides Section 2.2.8(1) |
The clause this row citesBAL-001-TRE-2, Requirements R9 and R10 and Section A, Introduction, 6. Background; see also Nodal Operating Guides Section 2.2.8(1) — “ The initial PFR performance (R9) measures the actual response compared to the expected response in the period from 20 to 52 seconds after an FME starts. The sustained PFR performance (R10) measures the best actual response between 46 and 60 seconds after t(0) compared to the expected response based on the system frequency at a point 46 seconds after t(0). … R10. Each Generator Owner shall meet a minimum 12-month rolling average sustained Primary Frequency Response performance of 0.75 on each generating unit/generating facility, based on participation in at least eight FMEs. ” (BAL-001-TRE-2 — Primary Frequency Response in the ERCOT Region, accessed 2026-07-28) | ||
| Continuous frequency band 58.8-61.2 Hz at the POIB Continuous operating range | Continuous operation band 58.8 Hz ≤ f ≤ 61.2 Hz (table row 'Minimum Ride-Through Time: continuous'). Time-limited bands adjoin it: 61.2 < f ≤ 61.6 Hz and 58.4 ≤ f < 58.8 Hz for 540 s; 61.6 < f ≤ 61.8 Hz and 57.0 ≤ f < 58.4 Hz for 299 s; beyond 61.8/57.0 Hz the Resource may ride through or trip. Binds all IBRs (including inverter-based ESRs), Type 1 WGRs and Type 2 WGRs connected to the ERCOT Transmission Grid, measured at the Resource's Point of Interconnection Bus (POIB). The parent §2.6.2 is titled 'Frequency Ride-Through Requirements for Generation Resources and Energy Storage Resources', so storage is bound explicitly. Note: ERCOT states the continuous band inside its frequency ride-through table - there is no separate steady-state frequency-range clause in the NOG. Provenance: the band figures are transcribed from the ride-through table the quote introduces, not from its running text. | Nodal Operating Guide §2.6.2.1(1), frequency ride-through table (Section 2 dated August 1, 2026; combined-PDF p.69) |
The clause this row citesNodal Operating Guide §2.6.2.1(1), frequency ride-through table (Section 2 dated August 1, 2026; combined-PDF p.69) — “ This Section applies to all IBRs, Type 1 WGRs and Type 2 WGRs connected to the ERCOT Transmission Grid. Such Resources shall ride through the frequency conditions at the Resource’s Point of Interconnection Bus (POIB) specified in the following table: ” (ERCOT Nodal Operating Guides, August 1, 2026, accessed 2026-08-08) | ||
| Continuous voltage band 0.90-1.10 pu at the POIB (ESR IBR table) Continuous operating range | Continuous operation voltage band 0.90 ≤ V ≤ 1.10 pu (RMS, p.u. of nominal) at the POIB, per Table B applicable to PVGRs and ESR IBRs (table row 'Minimum Ride-Through Time: continuous'). Binds transmission-connected IBRs subject to §2.9.1.1 (Preferred VRT: SGIA executed on/after 1-Aug-2024 or qualifying modifications); legacy IBRs under §2.9.1.2 Table A carry the same 0.90 ≤ V ≤ 1.10 continuous row (PDF p.95). Storage is bound explicitly: Table B is titled 'Applicable to PhotoVoltaic Generation Resources (PVGRs) and ESR IBRs'. As with frequency, ERCOT expresses the continuous voltage band inside its ride-through tables; the NOG has no separate steady-state voltage-range clause for resources. Provenance: the band figures are transcribed from Table B, which the quote introduces, not from its running text. | Nodal Operating Guide §2.9.1.1(1), Table B: Applicable to PhotoVoltaic Generation Resources (PVGRs) and ESR IBRs (Section 2 dated August 1, 2026; combined-PDF p.92) |
The clause this row citesNodal Operating Guide §2.9.1.1(1), Table B: Applicable to PhotoVoltaic Generation Resources (PVGRs) and ESR IBRs (Section 2 dated August 1, 2026; combined-PDF p.92) — “ All IBRs subject to this Section shall ride through the root-mean-square voltage conditions in Table A: Applicable to WGR IBRs, or Table B: Applicable to PhotoVoltaic Generation Resources (PVGRs) and ESR IBRs, below, as applicable, as measured at the IBR’s POIB: ” (ERCOT Nodal Operating Guides, August 1, 2026, accessed 2026-08-08) | ||
| Ramp-rate limit on deployments — wind/solar IRRs only; no ESR limit stated Ramp rate | Wind/solar IRRs only: <= 20% per minute of registered nameplate MW when responding to or released from an ERCOT deployment (compliance metric: >= 90% of eligible one-minute intervals with average ramp <= 25% of nameplate). ESRs carry no stated numeric ramp limit Binds Intermittent Renewable Resources (wind/solar) with an SGIA signed on/after 1 Jan 2009, and pre-2009 IRRs that control output other than by turbine stoppage; standalone ESRs carry NO stated numeric limit (their Normal/Emergency Ramp Rate curves are QSE-registered resource parameters); bracketed Section 6.5.7.11 extends the same limit to DC-Coupled Resources only upon system implementation of NPRR1029. The 90%/25% compliance metric is stated in the following paragraph of Section 6.5.7.10, cited but not quoted. | Nodal Protocols Section 6.5.7.10, IRR Ramp Rate Limitations, paragraph (1) |
The clause this row citesNodal Protocols Section 6.5.7.10, IRR Ramp Rate Limitations, paragraph (1) — “ Each IRR that is part of a Standard Generation Interconnection Agreement (SGIA) signed on or after January 1, 2009 shall limit its ramp rate to 20% per minute of its nameplate rating (MWs) as registered with ERCOT when responding to or released from an ERCOT deployment. ” (ERCOT Nodal Protocols, accessed 2026-07-28) | ||
| No RoCoF-based tripping or power reduction; IEEE 2800-2022 §7 incorporated for new IBRs RoCoF withstand | No numeric RoCoF withstand limit (Hz/s) is stated in the Nodal Operating Guide. Instead: (1) an IBR shall not use rate-of-change-of-frequency (or phase angle jump) measurement quantities as a basis for reducing power output or tripping offline during fault conditions and recovery within the ride-through profiles; (2) IBRs with an SGIA executed on or after 1-Aug-2024 shall meet or exceed IEEE 2800-2022 sections 5, 7 (Response to TS abnormal conditions) and 9. Binds transmission-connected IBRs, which include inverter-based Energy Storage Resources (the parent Section 2.9 is titled for 'Generation Resources and Energy Storage Resources' and §2.9.1.1(1) Table B is expressly 'Applicable to PhotoVoltaic Generation Resources (PVGRs) and ESR IBRs'). Applies at the Point of Interconnection Bus (POIB). The IEEE 2800-2022 incorporation applies to IBRs with SGIAs on/after 1-Aug-2024 or qualifying modifications; older IBRs implementing modifications complying with §2.9.1.2 before 1-Jan-2028 are excepted (§2.9.1(4)). | Nodal Operating Guide §2.9.1.1(7) (Section 2 dated August 1, 2026; combined-PDF p.93) + Nodal Operating Guide §2.9.1(2) (Section 2 dated August 1, 2026; combined-PDF p.90) |
The clauses this row citesNodal Operating Guide §2.9.1.1(7) (Section 2 dated August 1, 2026; combined-PDF p.93) — “ An IBR shall not use phase angle jump or rate-of-change-of-frequency measurement quantities as a basis for reducing power output or tripping offline during fault conditions and subsequent recovery to a steady-state operating point within the ride-through profiles specified in paragraph (1) above. ” (ERCOT Nodal Operating Guides, August 1, 2026, accessed 2026-08-08) Nodal Operating Guide §2.9.1(2) (Section 2 dated August 1, 2026; combined-PDF p.90) — “ An IBR with an SGIA executed on or after August 1, 2024 or that implements a modification, as described in paragraph (1)(c) of Planning Guide Section 5.2.1 for which a GIM was initiated on or after August 1, 2024, shall meet or exceed the capability and performance requirements in the following sections of Institute of Electrical and Electronics Engineers (IEEE) 2800-2022, Standard for Interconnection and Interoperability of Inverter-Based Resources (IBRs) Interconnecting with Associated Transmission Electric Power Systems (“IEEE 2800-2022 standard”), including any intra-standard cross references or definitions, unless otherwise clarified, modified, or exempted in the Protocols, these Operating Guides, or the Planning Guide: (a) Section 5, Reactive power-voltage control requirements within the continuous operation region; (b) Section 7, Response to TS abnormal conditions; and (c) Section 9, Protection. ” (ERCOT Nodal Operating Guides, August 1, 2026, accessed 2026-08-08) | ||
| Current injection during voltage ride-through; reactive-current prioritization relative to POIB voltage change Fault-current injection | No reduction of active current injection is permitted during voltage conditions requiring ride-through — the IBR shall inject electric current (except for primary-energy availability, frequency response, or as allowed in the paragraph). Outside the continuous operating voltage range the IBR continues delivering pre-disturbance active current unless reduction is needed for voltage support; any active-current reduction to prioritize reactive current shall be relative to the voltage change at the POIB. No numeric injection gain (k-factor, % current per % voltage) or response time for the injection is stated; ESRs charging must reduce or cease consumption to aid voltage recovery. Quote 1 binds transmission-connected IBRs under §2.9.1.1 (Preferred VRT); §2.9.1.2(4) (PDF p.95) imposes near-identical wording on legacy IBRs. Storage applicability: ESR IBRs are within IBR scope (Table B naming), and quote 2 (§2.9(3)) binds each Generation Resource and ESR directly, including an explicit charging-mode obligation - a storage-specific overlay. Later text in the same §2.9.1.1(4) paragraph (PDF p.93) adds that the IBR shall return to its pre-disturbance real power level no more than one second after POIB voltage recovers to normal operating range. | Nodal Operating Guide §2.9.1.1(4) (Section 2 dated August 1, 2026; combined-PDF p.93) + Nodal Operating Guide §2.9(3) (Section 2 dated August 1, 2026; combined-PDF p.89) |
The clauses this row citesNodal Operating Guide §2.9.1.1(4) (Section 2 dated August 1, 2026; combined-PDF p.93) — “ An IBR shall inject electric current when required to ride-through voltage conditions. Except when caused by reductions associated with intermittent primary energy source availability (e.g., wind speed or solar irradiance), an IBR shall not reduce active current injection during voltage conditions requiring ride-through unless allowed in this paragraph or to provide appropriate frequency response. When the POIB voltage is outside the continuous operating voltage range, an IBR shall continue to deliver pre-disturbance active current unless reduction is needed to allow for voltage support or otherwise specified by ERCOT or the interconnecting TSP. Any necessary reductions in active current to prioritize reactive current shall be relative to the voltage change at the POIB. ” (ERCOT Nodal Operating Guides, August 1, 2026, accessed 2026-08-08) Nodal Operating Guide §2.9(3) (Section 2 dated August 1, 2026; combined-PDF p.89) — “ During operating conditions listed in paragraph (1) above, each Generation Resource and ESR subject to paragraph (1) shall not, during and following a transient voltage disturbance, cease providing real or reactive current except to the extent needed to provide frequency support or aid in voltage recovery. Each ESR, if consuming active power from the ERCOT System when operating in the charging mode, shall reduce or cease power consumption as necessary to aid in voltage recovery during and following transient voltage disturbances. ” (ERCOT Nodal Operating Guides, August 1, 2026, accessed 2026-08-08) | ||
Who does ERCOT (NOG 2.9.1) bind, and since when?
Transmission-connected IBRs: PVGRs and ESR IBRs (ERCOT). Binds resources whose SGIA was executed on or after 1 Aug 2024.
These figures are a reading aid, not legal advice. Grid codes are reissued: verify against the current edition before you design to them.
Curve data last checked against the code on — 66 standards, 130 envelopes, published by bess.engineer under CC BY 4.0.
Questions this page answers about ERCOT (NOG 2.9.1)
- Does ERCOT (NOG 2.9.1) require ride-through, or only that the plant does not trip?
- Ride-through, for the envelopes on this page — that is what each of them is. It is not everything ERCOT (NOG 2.9.1) contains: the clauses quoted under the charts also address when the plant may or must trip. The requirement sentence under each chart says which side of the curve is the compliant one.
- Are the numbers on this page taken from ERCOT (NOG 2.9.1) itself?
- Every breakpoint is read from the code, and where a point was taken off a published figure rather than stated in the clause, the section under that chart says so — on this page that includes a breakpoint computed from the clause. The clause each curve came from is quoted under it.
- Which events are charted for ERCOT (NOG 2.9.1)?
- ERCOT (NOG 2.9.1) is charted here with 2 envelopes — low-voltage ride-through, high-voltage ride-through (LVRT, HVRT). No frequency envelope is charted here — check ERCOT (NOG 2.9.1) itself before concluding it sets none.
Ride-through, in context.
An envelope is a compliance boundary; understanding why it exists is a different question. The ride-through and grid-forming entries cover the engineering, and the Engineering Foundations course builds it from the physics up.
Also for the United States: NERC PRC-029-1 (IBR), NERC PRC-029-1 (Table 1: AC-connected wind IBR), Transient overvoltage (IEEE 2800 TOV), California Rule 21, ERCOT (NOG 2.6.2.1), ERCOT (NOG 2.9.1.2 legacy), and 5 more