Adaptive distance protection for lines connecting converter-interfaced renewable plants

Fault ride through compliance as imposed by grid codes prevents undesirable disconnection of renewable plants from the network even during fault. Diversified control schemes adopted in the converters associated with such plants modulate the voltage and current output significantly during a fault. This varies the fault characteristics of the renewable plant at times and thereby affects the performance of the distance relay protecting lines connected to such plants. In this article, a distance protection method using local data is proposed for transmission lines connecting renewable plants. The proposed method calculates the phase angle of faulted loop current by determining the pure-fault impedance of the renewable plant at every instant following fault detection, irrespective of the control scheme associated with the plant. Utilizing the information, it calculates the line impedance up to fault point accurately. Performance of the proposed adaptive protection method is tested on renewable-integrated modified 39-bus New England system using PSCAD/EMTDC simulated data and found to be accurate. Comparative assessment with the conventional distance relaying technique reveals its superiority.