Here is a summarised guide for conducting a short circuit calculation in inverter-based power plants according to IEC 60909:2016:
What is a Short Circuit Calculation?
A short circuit calculation for Inverter-Based Resources (IBRs), such as solar panels, wind turbines, and battery storage systems, focuses on determining the contribution of these resources to fault currents during a short circuit event. Unlike traditional synchronous generators, which provide substantial fault current, inverter-based resources behave differently.
A Summary Guide
- Represent the generator by the full-size converter, which reflects the behaviour of the inverter-based resource.
- Combine the generator and unit transformers as a single power station unit for the calculation.
- Ensure that the short circuit current at the busbar remains within its short circuit and mechanical ratings.
- Verify that the short circuit current is within the breaking capacity of all circuit breakers.
- Confirm that cable loading is less than 100% during all fault clearing times, ensuring that cables can handle the fault without damage.
- Note the steady-state short circuit current for further protection and stability studies. This value is critical for the correct operation of protective devices and ensuring system stability.
- Be aware that in meshed systems, the DC time constant of each section might differ from the cumulative system time constant. This could affect the short circuit current profile, so caution is needed during calculations.
This method ensures accurate calculation of short circuit currents in systems with inverter-based resources, which is crucial for effective system protection and stability. Following these steps will help ensure that all components in the system, including busbars, breakers, and cables, are adequately protected and that the system remains stable under fault conditions.
