Advanced voltage relay design for distance relay coordination in power networks equipped with low-inertia areas

Abstract

In modern power systems with high levels of distributed generation (DG), traditional protection schemes face challenges in ensuring reliable and efficient fault detection due to the complexities introduced by DG, particularly low-inertia sources such as wind power. This paper presents an advanced protection scheme that integrates voltage relays (VRs) rather than overcurrent relays (OCRs) to improve coordination with distance relays (DRs) and enhance fault detection across multiple protection zones. By utilizing voltage measurements instead of conventional current-based methods, the proposed scheme addresses issues such as low fault currents and mis-coordination, which are common in DG-integrated systems. The VR-DR coordination improves system reliability by increasing fault detection sensitivity and selectivity, reducing the risk of mis-coordination, and minimizing reliance on potentially inconsistent current measurements. VRs trigger faster fault isolation by operating before backup DRs, thus improving overall response times and system resilience. The VR scheme significantly outperforms traditional overcurrent relay schemes, with tripping times ranging from 0.002 to 0.956 s, compared to 0.035 to 1.184 s in the traditional scheme for three-phase faults in a CIGRE power network. Additionally, the total tripping time is reduced from 10.5 s in the traditional scheme to 3.2 s with the VR scheme in networks with DGs under line to line to ground fault. The study demonstrates that no mis-coordination events occurred with DRs in zone two, further emphasizing the effectiveness and reliability of the VR scheme. This innovative approach offers substantial improvements in fault management, ensuring quicker fault resolution and enhanced system stability in modern, DG-integrated power grids.