A Decade of Smart Medium Voltage Switchgear: LPITs and IEC 61850 Advancements

(LPITs) and IEC 61850-based digital communication.

LPITs such as Rogowski coil current sensors and resistive voltage dividers replace conventional instrument transformers, offering compact design, linear behaviour without saturation, and a wider dynamic range. These features improve measurement accuracy and protection performance while reducing energy losses and environmental impact. For example, replacing traditional CTs and VTs with LPITs can save up to 206,186 MWh over a 30-year lifecycle, equivalent to avoiding 74,639 tons of CO₂ emissions in a lineup of 10 panels.

The adoption of IEC 61850 standards, particularly GOOSE messaging and the Process Bus

(IEC 61850-9-2), has redefined MV switchgear architecture. Digital communication enables real-time data exchange, minimizes wiring, lowers installation costs, and supports flexible, future-proof protection schemes. Protection relays now can additionally act as Merging Units, transmitting sampled values over Ethernet, simplifying design and enhancing system reliability.

The paper addresses early technology gaps such as revenue metering compatibility, busbar differential protection, and broader IED type support and shows how recent advancements have closed them. LPITs now achieve accuracy classes (0.2/0.2S) suitable for revenue metering, and

MID-certified energy meter is available. Busbar differential protection has been optimized using sensor linearity and IEC 61850 communication, reducing switchgear footprint by up to 20%.

Standardization through the IEC 61869 family further accelerated LPIT adoption, ensuring interoperability between sensors and Intelligent Electronic Devices (IEDs). Today, IEDs supporting LPITs are used in a wide range of applications, including protection, control, power quality analysis, and energy metering. Field experience confirms the reliability and stability of these solutions, with thousands of panels installed globally. At the same time, IEC 61850-based systems have achieved significant adoption, reaching 80–90% penetration in primary substations.

Looking ahead, the paper highlights emerging trends such as centralized and virtualized protection architectures (CPC/VPC), enabled by Ethernet-based process buses. These developments promise even greater flexibility, scalability, and cost optimization for future substations.

In summary, Smart (Digital) MV Switchgear powered by LPITs and IEC 61850 delivers measurable benefits in operational efficiency, safety, and sustainability. Its proven reliability and interoperability make it a cornerstone technology for modern and future-ready electrical networks.