Overview
IEC TR 63401-4:2022 is a Technical Report from the IEC that addresses the behaviour of inverter-based resources (IBRs) - such as utility-scale PV and wind plants - during bulk grid faults. The document reviews existing grid-code fault-current requirements, analyses fault current generation by different IBR topologies and control schemes, and examines how large-scale IBR integration affects traditional relay protection performance.
Key topics and requirements
- Fault current requirements in grid codes: Reviews national and regional requirements (including NERC, China, Germany) for active and reactive current injection in both positive- and negative-sequence systems during symmetrical and unsymmetrical faults.
- IBR fault current behaviour: Analysis of current components at transient and fundamental frequencies for different converter architectures (full-scale converters, DFIG, PMSG etc.) and typical control strategies that shape fault response.
- Fault-ride-through (FRT) and control schemes: Discussion of common FRT solutions and AC current control approaches used to meet grid-code expectations during voltage dips and unbalanced conditions.
- Impact on relay protection: Evaluation of adaptability and limitations of existing protection functions with high IBR penetration, covering:
- Distance protection (power-frequency, time-domain, phase-comparison variants)
- Phase selectors (phase-difference and sequence-based selectors)
- Directional relays (phase and sequence based)
- Over-current protection
- Practical assessments and case studies: Simulation and measurement-based examples showing IBR behaviour during outgoing-line faults and bulk-grid disturbances.
Applications and users
This Technical Report is useful for:
- Grid operators and system planners assessing stability and protection coordination as IBR capacity increases.
- Protection engineers adapting or redesigning distance, directional and over-current protection schemes to account for reduced or altered fault currents from IBRs.
- Renewable plant designers and OEMs validating converter control strategies and FRT compliance with grid codes.
- Regulators and standard-makers comparing international fault-current and ride-through requirements.
- Researchers studying dynamic interactions between IBRs and legacy protection infrastructure.
Related standards and guidance
- Part of the IEC 63401 series on dynamic characteristics of IBRs in bulk power systems (see IEC for the latest list of parts).
- Complementary to national grid codes and regional requirements (NERC, Chinese standards, VDE) that specify fault current and ride-through performance.
Keywords: IEC TR 63401-4:2022, inverter-based resources, IBR fault behaviour, fault current, grid codes, fault-ride-through, relay protection, distance protection, over-current protection, DFIG, converter control.