Protection of six-phase transmission line using recursive estimation of non-linear autoregression model coefficients and decision tree

Ever-increasing energy demands and limited right of way over land motivates the adoption of six-phase power transmission. However, the wider recognition of six-phase transmission necessitates the development of a reliable protection system. Soaring assimilation of non-linear loads has complicated the protection task due to the intrusion of harmonics. This work aims at imparting necessary protection to six-phase transmission systems with immunity against harmonics. The issue pertaining to harmonics and sensor noise-induced non-linearity in the signal being fed to the protective relays has been addressed by modelling the current-voltage profile using a non-linear autoregression approach. Conventional relays are known to malfunction during non-linear loading and noisy measurement. In this context, an adaptive window-based approach has been employed to capture the non-linear dynamics, followed by mapping the model coefficients with the state of the six-phase system using decision trees. The inclusion of parameters in the non-linear auto regressive model for representing harmonic intrusion and noise imparts necessary robustness to the proposed protection scheme against non-linear loading and noisy sensor measurement. The appropriateness of the non-linear autoregression-based scheme has been tested for varying fault scenarios by considering wide variation in the fault attributes, non-linear loading, and noise level in the sensor measurement.