Design and Implementation of Numerical Relay to Provide Current and Voltage Protection for Electric Networks Using Raspberry Pi

This paper presents a comprehensive overview of the design, simulation, and real-time implementation of a numerical relay that provides overcurrent and over/undervoltage protection for power transmission and distribution networks. The Safety of the electrical network is greatly reliant on protective relays, with a particular emphasis on the IDMT (Inverse Definite Minimum Time) overcurrent relay. The IDMT relay is required to effectively isolate any faulty component from the operational system in the event of any issues or abnormalities. Additionally, ensuring stable operation in a power system necessitates the implementation of over/under voltage protection as a crucial aspect. The protection strategy implemented aims to mitigate potential harm to the power systems by effectively isolating faulty components. To ensure the prevention of overcurrent and overload issues, a conventional IDMT relay is employed. Additionally, voltage protection is ensured through the utilization of an inverse time delay relay. However, the proposed numerical relay offers the advantage of providing both protections at a reduced cost. To validate the efficacy of the coordinated control and protection process, Matlab/Simulink simulations have been conducted under different operating scenarios. CT and PT are utilized as current and voltage sensors, while the Raspberry Pi is programmed to execute the appropriate IDMT relay, including Standard Inverse-SI, very inverse-VI, and Extreme inverse-EI, as well as the Inverse time delay relay. The implementation and testing of IEEE/ANSI Codes 50 (Instantaneous Overcurrent Relay), 51 (AC Inverse Time Overcurrent Relay), 27 (Undervoltage Relay), and 59 (Overvoltage Relay) in accordance with IEC 60255 are conducted under diverse fault conditions.