Date of Award

6-2025

Degree Name

MS in Electrical Engineering

Department/Program

Electrical Engineering

College

College of Engineering

Advisor

Jason Poon

Advisor Department

Electrical Engineering

Advisor College

College of Engineering

Abstract

The purpose of this study is to explore the ability of a programmable logic controller (PLC) to wirelessly monitor and control power protection relays. The technologies surrounding power protection and industrial automation are ever evolving and have developed significantly in recent history. Industrial power applications call for consistent condition monitoring and status updates for various high-importance components. The high-importance components have power protection schemes that are managed by digital relays to trip circuit breakers in fault or unsafe operating conditions. The smart relays have a wide range of capabilities, including communications. Cal Poly assembled a collection of relays from Schweitzer Engineering Laboratories (SEL). PLCs are a common way to control, monitor, and automate several industrial processes. Cal Poly also acquired Schneider Electric PLC systems. The primary goal of this study is to connect the relays to the PLCs, specifically the SEL-710 Motor Protection Relay and the SEL-587Z High Impedance Differential Relay. These two options were selected because they both support the Modbus industrial communication protocol, which is natively supported on the Schneider PLCs. The PLC lab and the power protection lab are in different rooms, so the connection was established through the Schneider Trio JR900 Ethernet Radios. The first deliverable of this study is a lab, lecture, and pre-lab module created for the Cal Poly Industrial Automation and Control Course. The second contribution is an analysis to determine whether or not it is a practical topology to wirelessly monitor relays via PLC. Response time tests were conducted for fourteen test cases to discover delays associated with different parts of the communication network. Ultimately, the wireless connection was successful in reading live data and controlling settings from both relays. However, the results indicate that the topology is only practical for the SEL-710. The SEL-710 supports Modbus TCP Ethernet protocol and had a sufficiently fast response time to be deemed effective in application. On the other hand, the SEL-587Z only supports Modbus RTU serial protocol, which limits its response time, causing it to be out of the specified range for efficient operation.

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