Transmission Line Protection With Inverter-Based Resources

With the installed capacity of inverter-based resources (IBRs) increasing, such as wind and solar power, the fault characteristics of modern power systems keep evolving. Unlike synchronous generators (SGs) whose fault response is predictable from the physical laws of rotating machines with high inertia and overcurrent capability, the fault response of IBRs is based on the implemented fault-ride through (FRT) control, which depends on the adopted grid codes and how the control is specifically tailored by the manufacturer. This development challenges conventional transmission line protection schemes, particularly non-pilot protection schemes, where the interoperability issues are generally related to the low inertia and overcurrent capability of IBRs, as well as their heterogeneous fault responses. 

In this presentation, impacts of grid-forming (GFM) inverters on traditional apparent impedance-based distance protection are investigated. A time-domain distance protection implementation is presented, which has a proposed filtering process for enhanced interoperability with both GFM and grid-following (GFL) inverters. Next, a non-pilot time-domain protection scheme based on incremental quantities (IQs) is proposed and tested with extensive PSCAD/EMTDC simulations of two implemented GFM inverter control strategies. Lastly, a generic approach to model nonlinear GFM inverter control dynamics on IQ-based protection schemes is proposed and validated with PSCAD/EMTDC simulations of the same GFM inverters.