Canada (Alberta AESO) ride-through requirements
Low-voltage ride-through, High-voltage ride-through, Frequency ride-through for Canada. 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.
What is the low-voltage ride-through envelope for Canada (Alberta AESO)?
The plant must ride through 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 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 Generating facilities on the Alberta transmission system (AIES)
| 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 | no stated end | 0.9 pu | Held flat |
The clause this came from
AESO ISO Rules Section 503.5 Voltage Ride-Through, Appendix 1 'Voltage Ride-Through Requirements', Low Voltage Ride-Through Duration table: '< 0.45 / 4 to 9 cycles', '< 0.65 / 0.30 seconds', '< 0.75 / 2.00 seconds', '< 0.90 / 3.00 seconds', '>= 0.90 / Continuous operation'; plus subsection 2(2)(c). Effective 2024-04-01.
What is the high-voltage ride-through envelope for Canada (Alberta AESO)?
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 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.
The last band has no stated end time. The clause below states a continuous region — highlighted.
Applies to Generating facilities on the Alberta transmission system (AIES)
| 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
AESO ISO Rules Section 503.5, Appendix 1, High Voltage Ride-Through Duration table: '>= 1.200 / Instantaneous trip', '>= 1.175 / 0.20 seconds', '>= 1.15 / 0.50 seconds', '>= 1.10 / 1.00 seconds', '< 1.10 / Continuous operation'. Also subsection 2(2)(a): continuous operation between 0.90 and 1.10 pu. Effective 2024-04-01.
What is the frequency ride-through envelope for Canada (Alberta AESO)?
The plant must ride through between the upper and lower bands. The upper (over-frequency) band holds 61.7 Hz from t = 0 to 30 s; then 61.6 Hz from 30 s to 3 min; then 60.6 Hz from 3 min onward — the last band the envelope defines, with no stated end time. The lower (under-frequency) band holds 57 Hz from t = 0 to 750 ms; then 57.3 Hz from 750 ms to 7.5 s; then 57.8 Hz from 7.5 s to 30 s; then 58.4 Hz from 30 s to 3 min; then 59.4 Hz from 3 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; check which band it covers, because it is not always the last one.
Applies to Generating facilities on the Alberta transmission system (AIES)
Upper limit
| From | To | Frequency | Between the points |
|---|---|---|---|
| 0 | 30 s | 61.7 Hz | Held flat |
| 30 s | 3 min | 61.6 Hz | Held flat |
| 3 min | no stated end | 60.6 Hz | Held flat |
Lower limit
| From | To | Frequency | Between the points |
|---|---|---|---|
| 0 | 750 ms | 57 Hz | Held flat |
| 750 ms | 7.5 s | 57.3 Hz | Held flat |
| 7.5 s | 30 s | 57.8 Hz | Held flat |
| 30 s | 3 min | 58.4 Hz | Held flat |
| 3 min | no stated end | 59.4 Hz | Held flat |
The clause this came from
AESO ISO Rules Section 503.6, Appendix 1 'Trip Settings for Off-Nominal Frequency Protective Relays': High - '>=61.7 Instantaneous trip', '>=61.6 / 30', '>=60.6 / 180', '<60.6 Continuous operation'; Low - '<=57.0 Instantaneous trip', '<=57.3 / 0.75', '<=57.8 / 7.5', '<=58.4 / 30', '<=59.4 / 180', '>59.4 Continuous operation'. Contrast IESO Market Rules Appendix 4.2 Issue 16.0 category 1 'Off-Nominal Frequency Operation'.
Operating requirements beyond the envelopes.
The envelopes above are what Canada (Alberta AESO) demands during a disturbance. The rows below are the same regime’s operating and fault-response requirements — reactive capability, frequency response, continuous operating range and ramp rate — 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 |
|---|---|---|
| PF 0.90 supplying / 0.95 absorbing dynamic reactive power Reactive capability | Minimum reactive power capability: 0.9 power factor supplying dynamic reactive power and 0.95 power factor absorbing dynamic reactive power; for an energy storage resource (or aggregated facility containing one) the capability basis is both maximum authorized real power and maximum authorized charging power, over the entire real power operating range. Binds the legal owner of a generating unit, aggregated facility, or energy storage resource directly connected to the transmission system (or to transmission facilities within the City of Medicine Hat), per Section 503.3 §1(a) — storage is bound explicitly, by name. The 1.00 per-unit voltage reference for the requirements is the RMS phase-to-phase voltage at the stator winding terminal (generating unit / synchronous ESR) or the collector bus (aggregated facility), per §2(1); the rule does not state a point-of-interconnection PF measurement point. §2(6) additionally requires that limiters not be set to reduce this capability, and §2(7) allows ISO-approved external dynamic reactive resources to make up a shortfall. | Section 503.3, subsection 2(3) + Section 503.3, subsection 2(4)(b) |
The clauses this row citesSection 503.3, subsection 2(3) — “ The legal owner of a generating unit, aggregated facility, or energy storage resource must ensure that reactive power capability complies with the following minimum requirements: (a) 0.9 power factor, supplying dynamic reactive power; and (b) 0.95 power factor, absorbing dynamic reactive power. ” (AESO ISO Rules Section 503.3 Reactive Power (effective 2024-08-08), accessed 2026-08-08) Section 503.3, subsection 2(4)(b) — “ for an energy storage resource, or aggregated facility containing an energy storage resource, the maximum authorized real power and maximum authorized charging power of the energy storage resource or aggregated facility over the entire real power operating range. ” (AESO ISO Rules Section 503.3 Reactive Power (effective 2024-08-08), accessed 2026-08-08) | ||
| Governor droop 3-5%, deadband ±0.036 Hz Frequency response | Continuously acting governor system with droop setting ≥3% and ≤5%; for an aggregated facility containing an energy storage resource the droop basis is the greater of maximum authorized charging power or maximum authorized real power. Deadband (intentional plus unintentional) not exceeding ±0.036 Hz; no intentional time delay; manual setpoint adjustment range 59.4-60.6 Hz. Section 503.6 §3(1) binds the legal owner of an aggregated facility (AESO-defined term: an aggregation of 2 or more generating units or energy storage resources, or a combination thereof, each rated less than 9 MW, behind a common collector bus — which is how inverter-based BESS plants are structured); §3(1)(b)(ii) addresses storage explicitly via the MACP-vs-MARP droop basis. A parallel requirement for a generating unit or synchronous energy storage resource with MARP ≥ 10 MW sits in §2(1)(b)-(c): droop 3-5% based on maximum authorized real power, same ±0.036 Hz deadband. §6 requires operation with the governor in service, in droop mode, and free to respond while supplying active power or providing a frequency-responsive ancillary service. The manual setpoint-adjustment range of 59.4-60.6 Hz comes from the same Section 503.6 governor requirements but is not carried in the quoted text. The aggregated-facility definition is cited from the AESO Consolidated Authoritative Document Glossary and the 10 MW parallel-requirement threshold from §2(1)(b)-(c); neither is carried in the quoted text. | Section 503.6, subsection 3(1)(b) + Section 503.6, subsections 3(1)(c)-(d) |
The clauses this row citesSection 503.6, subsection 3(1)(b) — “ with a droop setting equal to or greater than 3% but less than or equal to 5%, where droop setting is based on: (i) maximum authorized real power, for an aggregated facility that does not contain an energy storage resource; or (ii) the greater of the maximum authorized charging power or maximum authorized real power, for an aggregated facility containing an energy storage resource. ” (AESO ISO Rules Section 503.6 Frequency & Speed Governing (effective 2026-07-10), accessed 2026-08-08) Section 503.6, subsections 3(1)(c)-(d) — “ with a deadband, intentional plus unintentional, not exceeding plus or minus 0.036 Hz; (d) not to have an intentional time delay added to the control system; ” (AESO ISO Rules Section 503.6 Frequency & Speed Governing (effective 2026-07-10), accessed 2026-08-08) | ||
| Governor response-rate cap and real-power-limit override Frequency response | The governor system of an aggregated facility must operate at a frequency response rate (MW/s) ≤ 5% of the difference between maximum authorized real power and maximum authorized charging power; it must monitor frequency at ≥ 20 samples/s with resolution of at least 0.004 Hz; and it must override any real power limits in effect during a frequency excursion, but only while frequency remains outside the deadband. Binds the legal owner of an aggregated facility (Section 503.6 §3(1)(f)-(h) and §3(2)). Storage is addressed via the MARP-MACP span in §3(1)(h) ('as applicable'), which for a BESS spans the full charge-to-discharge range — e.g. the cap is 5% of that span, per second. This is a maximum response rate, not a required minimum delivery time. The frequency-monitoring sampling-rate and resolution requirements are cited from §3(1)(f)-(g) (document p. 2) but are not carried in the quoted text. | Section 503.6, subsection 3(1)(h) + Section 503.6, subsection 3(2) |
The clauses this row citesSection 503.6, subsection 3(1)(h) — “ to operate at a frequency response rate, measured in MW/s, that is less than or equal to 5% of the difference between the maximum authorized real power and the maximum authorized charging power, as applicable. ” (AESO ISO Rules Section 503.6 Frequency & Speed Governing (effective 2026-07-10), accessed 2026-08-08) Section 503.6, subsection 3(2) — “ The legal owner of an aggregated facility must ensure that the governor system overrides any real power limits in effect at the time of the frequency excursion, but only while the frequency remains outside of the deadband. ” (AESO ISO Rules Section 503.6 Frequency & Speed Governing (effective 2026-07-10), accessed 2026-08-08) | ||
| Continuous voltage band 0.90-1.10 pu at HV side of step-up transformer Continuous operating range | Continuous operation between ≥0.90 and <1.10 per unit, where 1.0 pu is the RMS phase-to-phase voltage at the high-voltage side of the transmission system step-up transformer. Binds the legal owner of an energy storage resource, or aggregated facility containing one, that has a range greater than 5 MW between its maximum authorized charging power and maximum authorized real power and is directly connected to the transmission system (Section 503.5 §1(c)) — storage bound explicitly. Also binds generating units with MARP > 9.0 MW and aggregated facilities without storage (§1(a)-(b)). Only the continuous band is claimed here; the timed over/undervoltage ride-through steps of Appendix 1 are plotted in the LVRT/HVRT ride-through curve published for this code and are not repeated here. The 9.0 MW generating-unit applicability threshold is cited from §1(a)-(b) but is not carried in the quoted text. | Section 503.5, subsection 2(2)(a) + Section 503.5, subsections 2(1) and 1(c)(i) |
The clauses this row citesSection 503.5, subsection 2(2)(a) — “ continuous operation between greater than or equal to 0.90 and less than 1.10 per unit of the voltage value determined under subsection 2(1); ” (AESO ISO Rules Section 503.5 Voltage Ride-Through (effective 2024-04-01), accessed 2026-08-08) Section 503.5, subsections 2(1) and 1(c)(i) — “ determine the root mean square phase-to-phase voltage value at the high-voltage side of the transmission system step-up transformer, to be used as the 1.0 per unit voltage value. … has a range greater than 5 MW between its maximum authorized charging power and maximum authorized real power ” (AESO ISO Rules Section 503.5 Voltage Ride-Through (effective 2024-04-01), accessed 2026-08-08) | ||
| Frequency bands: continuous >59.4 to <60.6 Hz, timed bands to 57.0/61.7 Hz Continuous operating range | Continuous operation for frequency >59.4 Hz and <60.6 Hz. Time-limited no-trip bands (minimum withstand times before protective-relay trip is permitted): high side ≥60.6 Hz for 180 s, ≥61.6 Hz for 30 s, ≥61.7 Hz instantaneous trip permitted; low side ≤59.4 Hz for 180 s, ≤58.4 Hz for 30 s, ≤57.8 Hz for 7.5 s, ≤57.3 Hz for 0.75 s, ≤57.0 Hz instantaneous trip permitted. Binds the legal owner of a generating unit, aggregated facility, or energy storage resource (Section 503.6 §1(a) — storage bound explicitly) as design no-trip minimums per §5(1); §5(2) allows an alternative of binding firm arrangements to trip an equal MW of load if §5(1) is not achievable. The chart on PDF p.4 notes the area outside the 'No Trip Zone' is not a 'Must Trip Zone'. The timed bands are the same values the frequency ride-through envelope above plots; the continuous band (>59.4 to <60.6 Hz) is the continuous-operating-range datum this row records. | Section 503.6, subsection 5(1) and Appendix 1 + Section 503.6, Appendix 1 - Trip Settings for Off-Nominal Frequency Protective Relays (table transcription; columns Frequency (Hz) / Time (seconds)) |
The clauses this row citesSection 503.6, subsection 5(1) and Appendix 1 — “ The legal owner must, subject to subsection 5(2), design a generating unit, aggregated facility, or energy storage resource to not trip for under-frequency and over-frequency deviations for the minimum time frames as set out in Appendix 1. ” (AESO ISO Rules Section 503.6 Frequency & Speed Governing (effective 2026-07-10), accessed 2026-08-08) Section 503.6, Appendix 1 - Trip Settings for Off-Nominal Frequency Protective Relays (table transcription; columns Frequency (Hz) / Time (seconds)) — “ High Frequency Duration: >= 61.7 Instantaneous trip; >=61.6 30; >=60.6 180; <60.6 Continuous operation. Low Frequency Duration: <=57.0 Instantaneous trip; <=57.3 0.75; <= 57.8 7.5; <= 58.4 30; <= 59.4 180; > 59.4 Continuous operation. ” (AESO ISO Rules Section 503.6 Frequency & Speed Governing (effective 2026-07-10), accessed 2026-08-08) | ||
| Ramp-rate limiting controls required; no numeric limit in the rule Ramp rate | No numeric ramp-rate limit (MW/min or %/min) is stated in the rule, and no charge/discharge distinction is made; controls capable of limiting the ramp rate must be installed. Binds the legal owner under Section 503.6, whose applicability (§1(a)) expressly includes an energy storage resource directly connected to the transmission system. The one-sentence requirement establishes a capability obligation only; any actual ramp-rate values would be set outside this rule (e.g. in the ISO-approved functional specification under Section 503.1, which per §2(2) must be 'generally consistent' with Division 503 but may contain ISO-approved variances). | Section 503.6, section 4 (Ramp Rate Limitations) |
The clause this row citesSection 503.6, section 4 (Ramp Rate Limitations) — “ The legal owner must install controls that are capable of limiting the ramp rate. ” (AESO ISO Rules Section 503.6 Frequency & Speed Governing (effective 2026-07-10), accessed 2026-08-08) | ||
Who does Canada (Alberta AESO) bind, and since when?
Generating facilities on the Alberta transmission system (AIES). The LVRT clause quoted above carries the date of effect — "Effective 2024-04-01".
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 Canada (Alberta AESO)
- Does Canada (Alberta AESO) 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 Canada (Alberta AESO) 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 Canada (Alberta AESO) 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 Canada (Alberta AESO)?
- Canada (Alberta AESO) is charted here with 3 envelopes — low-voltage ride-through, high-voltage ride-through, frequency ride-through (LVRT, HVRT, FRT).
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 Canada: Ontario (IESO Market Rules App. 4.2), Quebec (Hydro-Quebec D-2022-088)
Elsewhere in North America: California Rule 21, Mexico (Codigo de Red), NERC PRC-024-4 (no-trip), NERC PRC-024-4 (Western), and 9 more