A Novel Directional Element for AC Lines in Systems with Inverter-Based Resources

Area of Science:

• Electrical Engineering
• Power Systems Protection
• Renewable Energy Integration

Background:

• Inverter-based resources (IBRs) alter fault characteristics, challenging conventional directional elements in power line protection.
• Existing directional elements (zero-sequence, negative-sequence) show poor adaptability to non-ground faults in IBR-connected systems.

Purpose of the Study:

• To propose a novel directional element for non-ground faults on AC lines in systems with IBRs.
• To enhance the adaptability and reliability of directional fault identification in modern power grids.

Main Methods:

• Analysis of positive-sequence measured impedance under fault conditions.
• Development of a control-protection coordinated method to regulate IBR fault current phase.
• Formulation of a unified directional criterion based on stable positive-sequence directional features.
• Verification through PSCAD/EMTDC simulations and dynamic model experiments.

Main Results:

• The proposed directional element accurately identifies fault direction for three-phase and phase-to-phase faults.
• The method demonstrates robustness against measurement noise and variations in grid strength.
• Stable and consistent positive-sequence directional features are established at line terminals.

Conclusions:

• The proposed directional element significantly improves non-ground fault-direction identification in IBR-connected AC lines.
• The control-protection coordinated approach ensures reliable operation of directional elements in IBR-dominated systems.
• The method offers enhanced adaptability compared to conventional directional elements.