A Grid That Must Do More - Possibilities, limits and risks for increasing transformer overload capability

	Hakim Dulac		Tara-Lee MacArthur		Ed teNyenhuis

 

Power systems worldwide are facing increasing demand from electrification, renewable generation, data centres and industrial growth. At the same time, utilities face growing challenges in delivering new infrastructure due to long equipment lead times, supply chain constraints and rising costs. As a result, industry is shifting from a traditional approach to one focused on making better use of existing assets. 

 

Transformers are central to this challenge. Transformers in the grid are typically operated below their rated capacity, ensuring spare capacity is available if a neighbouring transformer is lost. While this approach maintains reliability, it can leave significant capacity unused during normal operation.  

 

Historically, transformer overloads have been viewed as rare emergency events. However, the modern grid increasingly requires flexibility, not only during contingencies but also to support maintenance activities, accommodate changing power flows and manage network constraints. 

 

Importantly, our understanding of transformer behaviour has changed. Advances in thermal modelling, insulation ageing research, moisture assessment and online monitoring now provide much greater visibility into transformer condition than when many loading practices were originally developed. Technologies such as fibre-optic temperature monitoring, dissolved gas analysis (DGA) and moisture sensors provide an opportunity to move beyond static loading limits, building on the established guidance of IEC 60076-7 and IEEE C57.91 to enable more condition-based and risk-informed asset management.

 

Digital twins, together with advances in monitoring, sensors and thermal modelling, have the potential to improve understanding of transformer condition and overload capability. These tools may support more informed, risk-based decisions regarding asset loading in the future. During the 2026 CIGRE Paris Session, attendees gave feedback on what questions they would ask a transformer digital twin. The most common responses were remarkably consistent: What is my maximum load today? How much life remains? Am I fit for service? When do I need maintenance? These are the same questions utilities are asking as they seek to unlock additional capacity from existing fleets. 

 

Recognising the importance of this topic, CIGRE Study Committee A2 has established a new Joint Working Group A2/D1.82 to evaluate the potential for increasing long-time and short-time emergency loading limits through a structured Failure Modes, Effects and Criticality Analysis (FMECA). The work will examine ageing mechanisms, moisture behaviour, bubble formation risk, thermal modelling, component limitations, monitoring technologies and risk mitigation measures. The objective is not to simply increase loading limits, but to understand the possibilities, limitations, risks and consequences of increased transformer loading, and to provide a more transparent basis for decision-making. 

 

The potential benefits are significant: relieving network bottlenecks, deferring capital investment, improving system resilience and making better use of existing assets during the energy transition. However, these benefits must be balanced against the risks associated with increased temperatures, insulation ageing, component degradation and potential failure consequences. 

 

Transformers will play an increasingly important role in enabling network capacity. Through collaboration and the sharing of operational experience, CIGRE SC A2 aims to develop guidance that helps asset owners safely unlock the capability already available within their transformer fleets. The question is no longer whether transformers can do more, but how we can confidently and responsibly utilise that capability.