Reliable Power Grid Operation with Self-Monitoring Optical Current Transformers

Instrument Transformers (LPITs), particularly Optical Current Transformers (OCTs), as replacements for conventional electromagnetic current transformers. While previous studies have demonstrated the metrological advantages of OCTs and their suitability for conditionbased maintenance, less attention has been given to their role as self-monitoring cyber-physical assets within the IEC 61850 ecosystem and their contribution to sustainability and circular economy objectives in transmission and distribution (T&D) systems.

This paper presents the TECO Optical Current Transformer as a practical implementation of a self-monitoring OCT, combining optical sensing based on the Faraday effect with Rogowski coil measurements and an IEC 61850-compliant Merging Unit. Beyond measurement accuracy,

TECO operates as an active MMS server, continuously assessing its internal condition and reporting structured diagnostic information to supervisory and asset management systems. The hybrid measurement architecture enables real-time cross-validation of signals, supporting early fault detection, degradation trend analysis, and proactive maintenance strategies.

The paper discusses how MMS-based condition reporting transforms OCTs from passive measurement devices into intelligent nodes of the digital substation, enabling predictive maintenance, reducing operational risk, and extending equipment life. Furthermore, the impact of this approach on sustainability and circular economy is analyzed, highlighting reductions in material usage, avoidance of oil insulation, minimization of field interventions, and improved asset lifecycle management. The results demonstrate that self-monitoring OCTs such as TECO contribute not only to grid reliability but also to more sustainable and resilient T&D infrastructures.