Under-Frequency Load Shedding (UFLS)
The UFLS Program performance assessments include, but are not limited to the following practices:
- Are performed at least once every five years for each identified island
- Are based on the most recent UFLS Program data that is collected annually from the Distribution Providers connected to the ATC system
- Are based on the most recent under-frequency and over-frequency settings provided by Generation Owners connected to the ATC system, otherwise the setting limits given in the NERC PRC-025 Reliability Standard are assumed to apply
- Consider generation-load imbalance scenarios up to 25 percent within the identified island [per the NERC PRC-006 Reliability Standard]
- Use the Equivalent Inertia method for the frequency performance evaluation
- Use the assumptions of aggregate inertia range of 3.3 to 4.7, generator governor droop range from 12% to 18%, and load damping range of 1.0% to 2.0% in the Equivalent Inertia simulations
- Use the PSSE Dynamic Module method for the volts per hertz evaluation
- Use complex load modeling in the PSSE Dynamic Module simulations.
The Capacitor Bank Coordination assessments include, but are not limited to the following practices:
- Are performed at least once every five years for each identified island.
- Are based on the most recent UFLS Program data that is collected annually from the Distribution Providers connected to the ATC system.
- Are based on the most recent under-frequency and over-frequency settings provided by Generation Owners connected to the ATC system, otherwise the setting limits given in the NERC PRC-025 Reliability Standard are assumed to apply.
- Are based on the most recent over-voltage and under-frequency settings of shunt reactive power devices that are provided by ATC System Protection.
- Consider generation-load imbalance scenarios up to 25 percent within the identified island [per the NERC PRC-006 Reliability Standard].
- Use the PSSE Dynamic Module method for the voltage response evaluation.
- Use complex load modeling in the PSSE Dynamic Module simulations.