IMPACT OF PHOTOVOLTAIC POWER PLANTS EXCEEDING 75 MW ON THE PROTECTION OF TRANSMISSION LINES ABOVE 110 KV

Abstract

The intensive integration of renewable energy sources, particularly photovoltaic power plants with capacities exceeding 75 MW connected via inverter, necessitates a fundamental revision of relay protection strategies for high-voltage transmission lines (110 kV and above). This study provides a comprehensive analysis of how the behavior of power electronics influences the reliability of protection systems, contrasting IBR fault responses with those of traditional synchronous generators. A critical issue identified is the specific control logic of inverters, which limits short-circuit currents to 1.0–1.3 times the nominal value and suppresses negative and zero-sequence components, rendering standard fault detection algorithms ineffective. The authors develop a systematic classification of transmission line faults - categorized into electrical, mechanical, and natural groups - and evaluate the performance of classic current, distance, differential, and high-frequency protection schemes under high IBR penetration. Special attention is given to the lack of standardized inverter models, which complicates the verification of protection selectivity.

The practical value of the research is substantiated by a case study calculating distance protection settings for a 40 km, 110 kV line fed by an 80 MW PVPP. The simulation proves the failure of classical distance protection: due to current limiting, the relay measures an apparent impedance of 116.35 Ω against a Zone 1 setting of 16.636 Ω. This sevenfold deviation results in a failure to trip, confirming that standard impedance-based methods are unreliable for such network topologies.

Finally, the paper outlines promising trends for mitigating these risks, including the adoption of adaptive protection algorithms, wide area monitoring, protection and control (WAMPAC) systems, traveling-wave methods, and artificial intelligence to ensure the resilience of modern energy grids.