Revolutionizing Power Grid Modernization : The Impact of LPIT and Sensor Integration via Process Bus on Efficiency, Reliability, and Data Communication

Low Power Instrument Transformers (LPIT), as defined in the IEC 61869 standard family, and the implementation of digital process bus as per IEC 61850-9-2, are central technologies to the development of digital substations. LPITs provide digital measurement data with improved accuracy and safety over conventional instrument transformers, while the process bus enables the communication of time-critical information from primary devices to protection, automation, and control (PAC) systems over fiber optic networks.

In India, the innovative journey toward LPIT and process bus based digitization began in 2014, initiated by Power Grid Corporation of India Limited (POWERGRID), a national transmission public utility of the Government of India. It started with a pilot retrofitting project at the 400/220 kV Bhiwadi substation in Haryana, where digitization was implemented in a single 400 kV bay using optical current transformers (OCTs). Based on the experiences gained from this pilot project, POWERGRID successfully retrofitted and commissioned three fully digital substations operating at 765 kV, 400 kV, 220 kV, and 66 kV between 2020 and 2025 across various states in India. Numerous additional projects are also in the pipeline. Overall, these initiatives utilized both LPIT (Low Power Instrument Transformers) and conventional IT solutions, allowing the utility to better compare the effectiveness of LPIT and conventional instrument transformers. Despite various advantages, some challenges were also experienced during implementation and operational stages over the past decade, which are carefully outlined in this paper along with mitigation strategies.

These fully digital substation networks operate at the data-link layer and are connected to centralized remote centers for real-time control and monitoring, making them highly susceptible to cyberattacks. In response to the increasing number of cyberattack incidents at power stations worldwide, POWERGRID established a centralized ‘Integrated Indigenized Information

Security Operation Center’ (I3SOC) in 2023. This center collects and correlates logs from all operational technology (OT) assets in digital substations to enhance real-time monitoring. The logs are monitored and analyzed around the clock to ensure prompt alarm notifications via email, SMS, and voice call to the maintenance engineers.

Based on practical experience gained over the past decade and for a better understanding of

LPIT, process bus, and cybersecurity concerns together, this comprehensive technical paper highlights :

1. Brief fundamental principles underlying LPIT design and construction.

2. LPIT integration via Process Bus, adopted architecture, challenges, and mitigation strategy based on practical experience, 3. Advantages of LPITs in terms of accuracy, safety, reliability, capex, and operational efficiency compared to conventional instrument transformers, challenges, and practical mitigation strategies.

4. Cybersecurity considerations, evidence-based guidance, an introduction to

POWERGRID’s Indigenous cybersecurity solution “I3SOC”.