A Comparative Study of Smart THD-Based Fault Protection Techniques for Distribution Networks

Area of Science:

• Electrical Engineering
• Power Systems Engineering
• Control Systems

Background:

• Distributed Generators (DGs) improve power delivery but introduce bi-directional power flow, complicating traditional protection schemes.
• Conventional protection strategies require frequent relay setting adjustments due to network topology and operational mode changes.
• Novel fault protection techniques are essential for reliable operation and to prevent nuisance tripping in modern distribution systems.

Purpose of the Study:

• To compare two distribution system (DS) protection strategies utilizing Total Harmonic Distortion (THD) levels, estimated voltages, and zero-sequence components.
• To evaluate the effectiveness of these strategies, specifically those employing Multiple Second Order Generalized Integrator (MSOGI) and single SOGI (SOGI-THD), for fault detection, identification, and isolation.
• To assess the performance against conventional overcurrent and differential protection methods.

Main Methods:

• Development and simulation of two DS protection strategies using THD, estimated amplitude voltages, and zero-sequence components as fault indicators.
• Implementation of a Multiple Second Order Generalized Integrator (MSOGI) in the first strategy and a single SOGI in the second (SOGI-THD) for variable estimation.
• Utilizing communication lines between protective devices for coordinated protection and conducting simulations in MATLAB/Simulink under various fault conditions.

Main Results:

• The SOGI-THD method demonstrated high effectiveness in detecting and isolating faults within 6-8.5 ms.
• This method required minimal computational resources, executing in only 447 processor cycles.
• The SOGI-THD approach proved robust against harmonic distortion, accurately detecting faults even with pre-existing harmonic content.

Conclusions:

• The SOGI-THD protection strategy offers a superior solution for fault management in distribution systems with distributed generators.
• Its faster response time, lower computational burden, and robustness to harmonics make it advantageous over conventional methods.
• The integration of THD analysis provides a reliable indicator for advanced fault detection and isolation in smart grids.