Overview of the WECC transmission modeling
Zonal Transmission Network
Description
The WECC transmission network is modeled as transfer capacities between balancing authorities. Transfer limits and hurdles between zones are sourced from CPUC SERVM data, and wheeling tariffs between balancing areas are sourced from the WECC ADS dataset.
For future network evolution, the topology upgrades from NREL’s National Transmission Planning (NTP) study are incorporated. These planned topologies are held static for the interim years.
Assumptions and caveats
- Transmission expansion decisions are made exogenously to the model and are not determined by economic optimization algorithms.
- No speculative transmission buildout is included beyond published plans and targeted congestion-driven adjustments.
Data sources
| Source | Description | Link |
|---|---|---|
| CPUC SERVM | Transfer limits and hurdles between zones | CPUC SERVM |
| NREL NTP | Transmission upgrade data (CSV mapping + hierarchy) | NREL NTP |
| WECC ADS | Wheeling tariffs between balancing areas | WECC ADS |
Path Constraints
Description
CAISO uses path limits to manage power flows across major transmission interfaces. These constraints are designed to reflect grid stability limits and ensure system reliability.
Path constraints are modeled by mapping published path ratings onto the network represented in the model, using CPUC SERVM transfer limits. Each path aggregates the flow across its defined set of lines, and enforces a maximum allowable directional flow limit.
Assumptions and caveats
- Path flow limits are updated based on CAISO’s published seasonal ratings.
- Path constraints are represented at the zonal level, consistent with the overall model granularity.
Data Sources
| Source | Description | Link |
|---|---|---|
| CAISO OASIS | Historical curtailment and market report data for validation | CAISO OASIS |
| CPUC SERVM | Transfer limits defining path flow constraints | CPUC SERVM |