Expert Systems for Automated Relay Setting and Coordination in Transmission Lines and Power Transformers.

This article presents a set of expert systems that act as knowledge repositories, facilitating their reuse and understanding by new engineers and professionals in training.

Three expert systems are described that automate the configuration and coordination of distance, overcurrent and directional ground overcurrent (67N) protections in transmission lines and power transformers, integrating technical criteria, operational experience and optimization models. These systems, developed in Python, integrate expert knowledge accumulated and leverage optimization models to enhance the efficiency and accuracy of simulations and calculations. Beyond their technical functionality, these systems allow for documentation and explanation of every decision made, making them valuable educational tools for training new professionals in electrical protection.

Three expert systems were developed: Información Interna Distance Protection (21): This system automates the setting of distance relays from three manufacturers several references. It incorporates selectivity criteria, optimization functions, and operational experience through rules and constraints defined by senior engineers, and it simulates fault scenarios to validate the settings. Key constraints include fault detection at 50% and 99% of the line in Zones 1 and 2, respectively, and non-operation for faults at other voltage levels. This system allows users to visualize how technical criteria are applied in reallife situations, promoting case-based learning.

Directional Ground Overcurrent (67NCD): This system addresses the challenge of incorrect operations due to polarization errors in teleprotection-assisted schemes of 67NCD

(Directional comparison). It autonomously simulates faults across the influence area, statistically analyses detection accuracy, and selects the optimal polarization configuration with the lowest error rate. Its use allows to illustrate complex concepts such as polarization and its impact on the operation of protections.

Overcurrent Protection (51/51N): This tool calculates optimal settings for phase and ground overcurrent relays. It performs iterative coordination simulations under various network degradation scenarios, considering fault locations and impedances. The system outputs optimal settings and coordination times for all relays involved. This system facilitates understanding of the coordination between devices and the influence of failure points to operating times.

The settings obtained through the expert system, including primary and secondary values, are documented in the protection adjustment and coordination studies, enabling field personnel to accurately configure the equipment. Traditionally, these studies could take up to two days for just two relays. With the expert systems, the process is reduced to approximately three hours, significantly improving operational efficiency and freeing up human resources for other critical tasks.

Validation was conducted by comparing the system-generated settings against reliability, selectivity, and security criteria. The recommended settings were implemented in operational transmission lines and evaluated through simulations. Results confirmed that the automated settings met technical requirements, ensuring accurate fault detection and avoiding maloperations.

These expert systems represent a significant advance in the digital transformation of protection engineering. They not only reduce analysis time but also improve the quality and consistency of relay settings and constitute a powerful tool for technical knowledge management by integrating technical judgment and operational expertise into automated workflows