REAL-TIME PARTIAL DISCHARGE MONITORING AS AN EARLY-WARNING SYSTEM FOR SMART GIS SUBSTATIONS IN SAUDI ARABIA: PREVENTING FAILURES AND IMPROVING GRID RESILIENCE

Gas - insulated switchgear (GIS) occupies a strategically important position in compact, high-voltage substations, yet concealed insulation defects can develop before conventional protection operates. Partial discharge (PD) monitoring offers a means of recognising such deterioration during service, although detection alone does not establish failure imminence or guarantee outage avoidance. This critical review evaluates advances published between 2020 and 2025 in electromagnetic, acoustic, optical and gas-based PD sensing, alongside localisation, analytical classification and operational decision support. It synthesises the evidence through an engineering chain linking physical defects, trustworthy measurements, interpreted condition, intervention and electricity-service outcomes. The proposed framework differentiates signal detection from defect diagnosis and separates equipment reliability from system resilience. Particular consideration is given to intermittent discharges, sensor ageing, domain shift between laboratories and substations, alarm governance, cybersecurity and Saudi environmental and network conditions. The review argues for calibrated, multimodal monitoring with uncertainty - aware alarms and documented maintenance decisions, rather than unconditional reliance on automated classifications.