Intelligent Fault Detection in Smart Distribution Grids Using Bidirectional LSTM-CNN Ensemble

incorporating advanced metering infrastructure, distributed generation, and real-time supervisory control. Within this context, rapid and accurate fault detection and classification has acquired renewed urgency: the Bureau of Indian Standards estimates that uncleared distribution faults contribute approximately 31% of total technical losses on 11 kV feeders in Tier-2 Indian cities, and the average fault clearance time of 4.7 minutes in manually operated systems significantly exceeds the 0.5-minute target of SCADA-integrated digital relay systems. Traditional protective relay algorithms based on overcurrent and distance principles struggle with high-impedance faults, evolving distributed generation fault contributions, and complex multi-terminal feeder topologies that characterise modern Indian distribution networks.This study presents a deep learning-based fault detection and classification system combining Bidirectional Long Short-Term Memory (BiLSTM) networks for temporal feature extraction with a parallel one-dimensional Convolutional Neural Network (CNN-1D) for frequency-domain feature extraction, fused through a learned attention mechanism. The model is trained on 18,500 labelled fault events — covering six fault types (no-fault, LG, LL, LLG, 3LG, and open conductor) under 48 loading and generation scenarios — generated from a validated PSCAD/EMTDC model of the 47-bus Coimbatore zone 11 kV distribution network built from actual TNEB feeder data. SHAP (SHapley Additive exPlanations) values provide feature-level explainability for utility engineer acceptance.The proposed BiLSTM-CNN ensemble achieves 99.3% classification accuracy with 99.7% sensitivity, 99.1% specificity, and mean fault location error of 1.3% across all six fault classes, outperforming standalone LSTM (97.1%), CNN-1D (96.8%), and the SVM baseline (93.4%). Detection latency of 18.3 ms satisfies IEC 61850 GOOSE message timing requirements for digital substation protection, confirming practical deployment viability in Tamil Nadu's expanding smart grid infrastructure.