Gridraven provides three types of line ratings, allowing grid operators to transition from conservative static assumptions to high-precision dynamic capacity:
Rating Comparison and Grid Potential
To understand the operational advantage of Gridraven, it is essential to compare how different rating methods utilize the same physical asset over time.
| Rating Type | Temperature Aware | Wind Aware | Context and Usage |
| Seasonal (SR) | No | No | Fixed, worst-case assumptions used as a safe baseline. |
| Ambient Adjusted (AAR) | Yes | No | Ratings computed with forecasted ambient temperature. |
| Dynamic (DLR) | Yes | Yes | Maximum capacity unlocked by accounting for hyper-local wind cooling. |
Figure 1. Aggregated Line Ratings Over Time. This graph illustrates the "capacity gap." The Seasonal Rating (SR) remains a flat, conservative floor. The Ambient Adjusted Rating (AAR) provides a slight uplift based on temperature. The Dynamic Line Rating (DLR) shows significant peaks, often doubling the capacity during periods of high wind.
How the ratings are calculated?
Gridraven Claw is configured by default with the following AAR and DLR parameters used as the basis for forecast calculations.
These can be adjusted if necessary (an upcoming update will allow each organization to manage their own parameters, but currently this must be done via the development team).
| Topic | Parameter | Default value | Is configurable? | Description |
|---|---|---|---|---|
| 0 – General | Thermal Model Name | GridRaven | YES | Other options: Cigre207, Cigre601, EEE738_2012, IEEE738_2023 |
| Unit System | metric | YES | Other option: imperial | |
| Frequency (Hz) | 50.0 | YES | Other option: 60 Hz | |
| Max Reynolds Number | 50000 | How it's used: Caps the maximum Reynolds number passed into the Nusselt forced convection correlations. Why: The empirical Nusselt piecewise correlations (like those in CIGRE TB 601 Table 4) are formally bounded. Going beyond the tested Re values risks wildly extrapolating heat transfer beyond verified wind tunnel physics. | ||
| 1 – Dynamic Line Rating (DLR) | Minimum Wind Speed (m/s) | 0.61 | How it's used: Any wind speed in the weather input below this value is artificially clipped up to this floor during steady-state calculations. Why: 0.61 m/s (exactly 2.0 ft/s) is the classic conservative baseline wind speed defined in IEEE 738 and CIGRE TB 299 for calculating Static Line Ratings (SLR). | |
| Angle of Attack Low Speed Threshold (m/s) | 2.0 | How it's used: If the wind speed is less than this threshold, the true wind direction is ignored, and the angle of attack is forced to the angle_of_attack_target_angle. Why: At very low wind speeds, the wind physically meanders, changing direction chaotically across the span. Both CIGRE TB 601 and CIGRE TB 969 (Sections 3.8 and 3.9) note that low-wind direction data (whether from sensors or weather models) is highly uncertain. The true effective cooling approaches an asymptotic constant rather than following instantaneous point measurements or highly granular forecasts. | ||
| Angle of Attack Target Angle (°) | 30.0 | How it's used: The forced angle of attack when wind speeds drop below the angle of attack low speed threshold. Why: CIGRE TB 207 and CIGRE TB 969 explicitly recommend a fixed angle of attack of 45 degrees during periods of low, meandering wind. Statistical analysis of wind standard deviations shows that the chaotic swirling of air over a span produces a continuous cooling effect equivalent to a steady 38-to-45 degree wind. Overwriting to 45 degrees (with 30 degrees being more conservatie) ensures a stable, physically realistic rating baseline, preventing artificially high ratings if a probabilistic forecast or sensor suggests 90 degrees, and preventing overly conservative ratings if it suggests 0 degrees. | ||
| Minimum Attack Angle (°) | 30.0 | How it's used: Provides a hard floor for the final effective angle of attack when the wind speed is above the angle of attack low speed threshold Why: Used to avoid worst-case conservative scenarios and reflects the variability of wind direction within an hour. | ||
| Solar Mode | thermal model specific | |||
| Clearness Ratio | 1.0 | Can come from forecast also. 1.0 Means clear-sky | ||
| Temperature (°C) | forecast | |||
| Wind Speed | forecast | |||
| Wind Direction | forecast | |||
| 2 – Ambient-Adjusted Rating (AAR) | Wind Speed | 0.61 | YES | |
| Wind Direction | 90.0 | YES | ||
| Clearness Ratio | 1.0 | Can come from forecast also. 1.0 Means clear-sky | ||
| Solar Mode | constant | YES | Other options: thermal model specific, simple day night, sunrise sunset based | |
| Solar Irradiance Constant (W/m2) | 1000.0 | YES | ||
| Daytime Solar Irradiance (W/m2) | 1000.0 | YES | ||
| Nighttime Solar Irradiance(W/m2) | 0.0 | YES | ||
| Day Start Hour (Local Time) | 6.0 | YES | ||
| Day End Hour (Local Time) | 18.0 | YES | ||
| 3 – Static Ratings | Temperature (°C) | 35.0 | ||
| Wind Speed (m/s) | 0.61 | YES | ||
| Wind Direction | 90.0 | YES | ||
| Solar Irradiance | 1033.0 | YES | ||
| Clearness Ratio | 1.0 | YES | ||
| 4 – Short-Term Emergency Rating | Normal Current Mode | percentage_of_reference_rating | YES | Other option: fixed amperes |
| Normal Fixed Current (A) | 1000.0 | YES | ||
| Normal Current Percentage | 84.0 | YES | ||
| Normal Current Reference Rating | dlr_mean | YES | Other options: dlr50, dlr75, dlr90, dlr95, dlr98, dlr99, aar | |
| Emergency Duration (min) | 15.0 | YES | ||
| Emergency Temperature Limit Mode | addition_to_max_conductor_temp | YES | Other option: fixed Temperature | |
| Fixed Emergency Temperature Limit (C’) | 120 | YES | ||
| Emergency Temperature Addition (C’) | 15.0 | YES | ||
| Time Step Interval (dt minutes) | 1.0 | YES | ||
| 5 – Long-Term Emergency Ratings | Normal Current Mode | percentage_of_reference_rating | YES | Other option: fixed amperes |
| Normal Fixed Current (A) | 1000.0 | YES | ||
| Normal Current Percentage | 84.0 | YES | ||
| Normal Current Reference Rating | dlr_mean | YES | Other options: dlr50, dlr75, dlr90, dlr95, dlr98, dlr99, aar | |
| Emergency Duration (min) | 120.0 | YES | ||
| Emergency Temperature Limit Mode | addition_to_max_conductor_temp | YES | Other option: fixed temperature | |
| Fixed Emergency Temperature Limit (°C) | 110.0 | YES | ||
| Emergency Temperature Addition (°C) | 10.0 | YES | ||
| Time Step Interval (dt minutes) | 1.0 | YES | ||
| 6 – Temperature Tracking | Current Input Mode | input | YES | Other options: fixed amperes, percentage of reference rating |
| Fixed Current (A) | 800.0 | |||
| Current Percentage | 100.0 | YES | ||
| Current Reference Rating | dlr_mean | YES | Other options: dlr50, dlr75, dlr90, dlr95, dlr98, dlr99, aar | |
| Initial Temperature (°C) | 25.0 |
An example:
| DLR Dynamic Line Rating | AAR Ambient Adjusted Rating | SR Seasonal or Static Rating | |
|---|---|---|---|
| Wind speed | Gridraven prediction, but no less than 0.61 m/s | 0.61 m/s | Configured by customer |
| Wind direction | Gridraven prediction, but no less than 30°. At under 2 m/s speeds the angle is fixed to 30°. | 90° | Configured by customer |
| Outside air temperature | From weather forecast | From weather forecast | Configured by customer |
| Solar irradiation | Clear sky model, up to 1033 W/m2, but accounting with sun’s position and conductor azimuth | 1000 W/m2 | Configured by customer |
| Forecast horizon | Up to 72 hours ahead, depending on the region | Up to 240 hours ahead | |
| Conductor type | Configured by customer with span-level resolution | Configured by customer with span-level resolution | Configured by customer with span-level resolution |
| Clearance limits | Maximum operating temperature of each span is configured by customer | Maximum operating temperature of each span is configured by customer | Maximum operating temperature of each span is configured by customer |