Curtailment Event Tracking
Curtailment is a material risk for IPPs and traders. ODS-E provides fields to track curtailment events, their causes, and estimated lost generation at the interval level.
Context
The SAETA “Policy to Power” report notes that the GCAR congestion curtailment mechanism (capped at 4%) is active in the Western and Eastern Cape. Over 100 curtailment events were recorded this financial year, up from fewer than 30 the prior year. IPPs are compensated through existing ancillary-services frameworks, with recoverable costs capped under MYPD6 (Actions 5, 8).
Timeseries Fields
| Field | Type | Description |
|---|---|---|
curtailment_flag |
boolean | Whether generation was curtailed during this interval |
curtailment_type |
enum: congestion, frequency, voltage, instruction, other |
Reason for curtailment |
curtailed_kWh |
number >= 0 | Estimated generation lost to curtailment during this interval |
curtailment_instruction_id |
string | Reference to the system operator dispatch instruction |
Usage Notes
curtailed_kWhrepresents estimated lost production, not metered output. It is typically derived from forecasted or rated output minus actual metered generation.curtailment_typevalues:congestion– network capacity constraint (the GCAR mechanism)frequency– system frequency managementvoltage– local voltage regulationinstruction– direct system operator dispatch instructionother– any other cause
- When
curtailment_flagistrue, thekWhfield reflects actual metered output (reduced), whilecurtailed_kWhreflects the estimated shortfall.
Example
{
"timestamp": "2026-02-17T12:30:00+02:00",
"kWh": 62.1,
"error_type": "normal",
"direction": "generation",
"curtailment_flag": true,
"curtailment_type": "congestion",
"curtailed_kWh": 41.4,
"curtailment_instruction_id": "NTCSA-GCAR-2026-02-17-0034"
}