NERC PRC-029-1 (IBR) ride-through requirements

Low-voltage ride-through, High-voltage ride-through, Frequency ride-through for the United States. Every breakpoint below is read from the code itself, and carries the clause it came from — so you can check it, not just cite it.

3Envelopes
LVRT · HVRT · FRTEvents
Transmission Connection level
LVRT

What is the low-voltage ride-through envelope for NERC PRC-029-1 (IBR)?

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 0.25 pu from 320 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.

Every breakpoint is stated in the clause cited below.

Applies to BES inverter-based resources; valid for RoCoF ≤ 5 Hz/s

NERC PRC-029-1 (IBR) — low-voltage ride-through envelopeNERC PRC-029-1 (IBR) low-voltage ride-through envelope. The plant must ride through for any voltage that stays on or above the line; below it, the envelope no longer applies. Logarithmic time axis from 0.01 s to 20 s; linear voltage axis in per-unit. The first band applies from the instant of the event (t = 0). The envelope holds 0 pu from t = 0 to 320 ms; then 0.25 pu from 320 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 (drawn as an open dashed tail).NERC PRC-029-1 (IBR) — low-voltage ride-through envelopenominal 1.00 pu0.010.11100.000.200.400.600.801.001.20Time from event start (s, log scale) · first band applies from t = 0Voltage (pu)0.9 puMUST RIDE THROUGHmust ride through on or above the lineopen — no stated end time
Low-voltage ride-through envelope for NERC PRC-029-1 (IBR). Time runs on a logarithmic axis. Scroll the chart sideways for the rest of the time axis →
Low-voltage ride-through breakpoints for NERC PRC-029-1 (IBR)
From To Voltage Between the points
0 320 ms 0 pu Held flat
320 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

NERC PRC-029-1, Attachment 1 'Voltage Ride-Through Criteria', Table 2 'Voltage Ride-through Requirements for All Other IBR' (p.12), with Boundary Details bullets 2(b) (PV+BESS → Table 2), 7 and 11 (p.13).

HVRT

What is the high-voltage ride-through envelope for NERC PRC-029-1 (IBR)?

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 to 30 min; then 1.05 pu from 30 min onward — the last band the envelope defines, with no stated end time.

The last band has no stated end time. The clause below states a continuous region — highlighted.

Applies to BES inverter-based resources; valid for RoCoF ≤ 5 Hz/s

NERC PRC-029-1 (IBR) — high-voltage ride-through envelopeNERC PRC-029-1 (IBR) high-voltage ride-through envelope. The plant must ride through for any voltage that stays on or below the line; above it, the envelope no longer applies. Logarithmic time axis from 0.1 s to 10000 s; linear voltage axis in per-unit. The first band applies from the instant of the event (t = 0). The envelope holds 1.2 pu from t = 0 to 1 s; then 1.1 pu from 1 s to 30 min; then 1.05 pu from 30 min onward — the last band the envelope defines, with no stated end time (drawn as an open dashed tail).NERC PRC-029-1 (IBR) — high-voltage ride-through envelopenominal 1.00 pu0.11101001000100000.951.001.051.101.151.201.25Time from event start (s, log scale) · first band applies from t = 0Voltage (pu)1.05 puMUST RIDE THROUGHmust ride through on or below the lineopen — no stated end time
High-voltage ride-through envelope for NERC PRC-029-1 (IBR). Time runs on a logarithmic axis. Scroll the chart sideways for the rest of the time axis →
High-voltage ride-through breakpoints for NERC PRC-029-1 (IBR)
From To Voltage Between the points
0 1 s 1.2 pu Held flat
1 s 30 min 1.1 pu Held flat
30 min no stated end 1.05 pu Held flat
The clause this came from

NERC PRC-029-1, Attachment 1, Table 2 'Voltage Ride-through Requirements for All Other IBR' (p.12), rows '>1.20 N/A', '>1.10 Mandatory Operation Region 1.0', '>1.05 Continuous Operation Region 1800'.

FRT

What is the frequency ride-through envelope for NERC PRC-029-1 (IBR)?

The plant must ride through between the upper and lower bands. The upper (over-frequency) band holds 61.8 Hz from t = 0 to 299 s; then 61.2 Hz from 299 s onward — the last band the envelope defines, with no stated end time. The lower (under-frequency) band holds 57 Hz from t = 0 to 299 s; then 58.8 Hz from 299 s onward — the last band the envelope defines, with no stated end time.

Every breakpoint is stated in the clause cited below.

Applies to BES inverter-based resources; valid for RoCoF ≤ 5 Hz/s

NERC PRC-029-1 (IBR) — frequency ride-through envelopeNERC PRC-029-1 (IBR) frequency ride-through envelope. The plant must ride through for any frequency that stays between the lower and upper bands. Logarithmic time axis from 10 s to 1000 s; linear frequency axis in hertz. The first band applies from the instant of the event (t = 0). upper (over-frequency) band: holds 61.8 Hz from t = 0 to 299 s; then 61.2 Hz from 299 s onward — the last band the envelope defines, with no stated end time (drawn as an open dashed tail). lower (under-frequency) band: holds 57 Hz from t = 0 to 299 s; then 58.8 Hz from 299 s onward — the last band the envelope defines, with no stated end time (drawn as an open dashed tail).NERC PRC-029-1 (IBR) — frequency ride-through envelopenominal 60 Hz10100100020502005005657585960616263Time from event start (s, log scale) · first band applies from t = 0Frequency (Hz)61.2 Hz58.8 HzMUST RIDE THROUGHUpper band (over-frequency)Lower band (under-frequency)must ride through between the bandsopen — no stated end time
Frequency ride-through envelope for NERC PRC-029-1 (IBR). Time runs on a logarithmic axis. Scroll the chart sideways for the rest of the time axis →

Upper limit

Frequency ride-through breakpoints for NERC PRC-029-1 (IBR) — Upper limit
From To Frequency Between the points
0 299 s 61.8 Hz Held flat
299 s no stated end 61.2 Hz Held flat

Lower limit

Frequency ride-through breakpoints for NERC PRC-029-1 (IBR) — Lower limit
From To Frequency Between the points
0 299 s 57 Hz Held flat
299 s no stated end 58.8 Hz Held flat
The clause this came from

NERC PRC-029-1, Attachment 2 'Frequency Ride-Through Criteria', Table 3 'Frequency Ride-through Capability Requirements' and Figure 1 'PRC-029 Frequency Ride-through Requirements' (p.14); Requirement R3 caps applicability at RoCoF ≤ 5 Hz/s.

Scope

Who does NERC PRC-029-1 (IBR) bind, and since when?

BES inverter-based resources; valid for RoCoF ≤ 5 Hz/s. Enforceable from 1 Oct 2026 (FERC Order No. 909).

These figures are a reading aid, not legal advice. Grid codes are reissued: verify against the current edition before you design to them.

Digitised operating parameters beyond ride-through — droop, reactive capability, operating ranges — are published for 36 of the 66 codes in this atlas, not yet for NERC PRC-029-1 (IBR). That is a gap on this site, not a statement that NERC PRC-029-1 (IBR) sets none — the atlas hub marks the codes that carry them.

Curve data last checked against the code on — 66 standards, 130 envelopes, published by bess.engineer under CC BY 4.0.

Questions

Questions this page answers about NERC PRC-029-1 (IBR)

Does NERC PRC-029-1 (IBR) require ride-through, or only that the plant does not trip?
Ride-through. Every envelope on this page is a performance duty the plant must meet, not a protection-setting no-trip boundary — they are different obligations. That is what these curves are; they are not everything NERC PRC-029-1 (IBR) contains. The requirement sentence under each chart says which side of the curve is the compliant one.
Are the numbers on this page taken from NERC PRC-029-1 (IBR) itself?
Yes. Every breakpoint is read from the code, and each envelope carries the clause it came from, quoted in full under its chart — so you can check the figure against the standard rather than cite it from this page.
Which events are charted for NERC PRC-029-1 (IBR)?
NERC PRC-029-1 (IBR) is charted here with 3 envelopes — low-voltage ride-through, high-voltage ride-through, frequency ride-through (LVRT, HVRT, FRT).
Related

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-024-4 (Western), ERCOT (NOG 2.6.2.1), ERCOT (NOG 2.9.1.2 legacy), ERCOT (NOG 2.9.1), IEEE 1547-2018 Cat III, IEEE 2800-2022, and 5 more

All 66 grid codes Open the chart