NERC PRC-024-4 (no-trip) limits
Low-voltage boundary, High-voltage boundary 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 — an envelope that stops where its published chart stops. Every envelope here is a protection-setting no-trip boundary, not a ride-through performance duty — they are different obligations.
What is the low-voltage boundary for NERC PRC-024-4 (no-trip)?
The plant must not trip for any voltage that stays on or above this envelope. The envelope holds 0 pu from t = 0 to 150 ms; then 0.45 pu from 150 ms to 300 ms; then 0.65 pu from 300 ms to 2 s; then 0.75 pu from 2 s to 3 s; then 0.9 pu from 3 s, plotted to 4 s.
A no-trip boundary: protection must not operate inside this envelope. The envelope stops where the published chart stops; the code states no end time.
Applies to BES generating resources; relay no-trip settings (GO duty)
| From | To | Voltage | Between the points |
|---|---|---|---|
| 0 | 150 ms | 0 pu | Held flat |
| 150 ms | 300 ms | 0.45 pu | Held flat |
| 300 ms | 2 s | 0.65 pu | Held flat |
| 2 s | 3 s | 0.75 pu | Held flat |
| 3 s | plotted to 4 s | 0.9 pu | Held flat |
The clause this came from
NERC PRC-024-4, Attachment 2 'Voltage No-Trip Boundaries – Eastern, Western, and ERCOT Interconnections', Table 5 'Voltage Boundary Data Points' (p.16) and Figure 5 callout. Identical table appears in PRC-024-3 (p.10, 'Voltage Boundary Data Points'), so the correction holds under either edition.
What is the high-voltage boundary for NERC PRC-024-4 (no-trip)?
The plant must not trip for any voltage that stays on or below this envelope. The envelope holds 1.2 pu from t = 0 to 200 ms; then 1.175 pu from 200 ms to 500 ms; then 1.15 pu from 500 ms to 1 s; then 1.1 pu from 1 s onward — the last band the envelope defines, with no stated end time.
A no-trip boundary: protection must not operate inside this envelope. Every breakpoint is stated in the clause cited below.
Applies to BES generating resources; relay no-trip settings (GO duty)
| From | To | Voltage | Between the points |
|---|---|---|---|
| 0 | 200 ms | 1.2 pu | Held flat |
| 200 ms | 500 ms | 1.175 pu | Held flat |
| 500 ms | 1 s | 1.15 pu | Held flat |
| 1 s | no stated end | 1.1 pu | Held flat |
The clause this came from
NERC PRC-024-4 Section A.1 Title, A.4 Applicability 4.2.1–4.2.3, Requirement R2, and Attachment 2 Table 5 (p.16).
Who does NERC PRC-024-4 (no-trip) bind, and since when?
BES generating resources; relay no-trip settings (GO duty). No date of effect is published here — grid codes are reissued, so check the current issue before relying on it.
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-024-4 (no-trip). That is a gap on this site, not a statement that NERC PRC-024-4 (no-trip) 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 this page answers about NERC PRC-024-4 (no-trip)
- Does NERC PRC-024-4 (no-trip) require ride-through, or only that the plant does not trip?
- Every envelope here is a protection-setting no-trip boundary, not a ride-through performance duty — they are different obligations. Protection must not operate inside the envelopes plotted on this page.
- Are the numbers on this page taken from NERC PRC-024-4 (no-trip) 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 an envelope that stops where its published chart stops. The clause each curve came from is quoted under it.
- Which events are charted for NERC PRC-024-4 (no-trip)?
- NERC PRC-024-4 (no-trip) is charted here with 2 envelopes — low-voltage boundary, high-voltage boundary (LVRT, HVRT). No frequency envelope is charted here — check NERC PRC-024-4 (no-trip) itself before concluding it sets none.
No-trip limits, 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 (ERCOT), 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