Electrical and Computer Engineering ETDs

Publication Date

Summer 7-28-2026

Abstract

As Distributed Energy Resources (DERs) proliferate on the grid, they're straining a part of the power system that critical facilities—hospitals, transit systems, and data centers—depend on: secondary networks protected by Network Protector Units (NPUs). These protectors were built for one-way power flow, so when DERs push power backward under normal conditions, they can mask real faults, especially ground faults through Delta-Wye transformers. This dissertation tackles the problem from three angles. First, a Direct Transfer Trip scheme relays fault data directly from feeder relays to NPUs, validated through hardware-in-the-loop testing though its reliance on communication networks introduces cyberattack risks, which we also quantify. Second, a communication-free method uses impedance and sequence-current signatures to tell real faults apart from DER-driven reverse flow. Third, we test compensator distance protection on commercial relays, finding it works well for phase faults but less so for ground faults. Together, these methods offer a practical path toward securing secondary networks as DER adoption grows.

Keywords

Power System Protection, Secondary Network Protection, Distributed Energy Resources (DERs), Direct Transfer Trip (DTT), Network Protector Units (NPUs), Hardware in the Loop (HIL), Cyber Security, Power System Resilience, Relay Coordination

Project Sponsors

This work supported by the Sandia National Laboratories’ Laboratory Directed R&D (LDRD) 24-0759 funding and National Science Foundation under awards #ECCS 2338555 and #OISE 2330582. This dissertation has been authored by an employee of National Technology & Engineering Solutions of Sandia, LLC under Contract No. DE-NA0003525 with the U.S. Department of Energy (DOE).

Document Type

Dissertation

Language

English

Degree Name

Electrical Engineering

Level of Degree

Doctoral

Department Name

Electrical and Computer Engineering

First Committee Member (Chair)

Prof. Ali Bidram

Second Committee Member

Prof. Michel Devetsikiotics

Third Committee Member

Prof. Ramiro Jordan

Fourth Committee Member

Dr. Farzad Ferdowsi

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Available for download on Friday, July 28, 2028

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