This part of IEC 63401, which is a technical report, mainly focuses on the fault behaviour of IBRs and performances of the existing relay protection in grids with large-scale integration of IBRs.

This document mainly includes:
- The IBR fault current requirements in present grid codes, including the requirements of active and reactive currents in positive- and negative-sequence systems during symmetrical and unsymmetrical faults.
- Fault current behaviour of IBRs, including the current components in transient and fundamental frequency in different IBR topology and control schemes.

Adaptability of existing relay protection with the large-scale integration of IBRs, including the performances of distance protection, phase selector, directional relay and over-current protection.