Investigating the Vulnerabilities of the Direct Transfer Trip Scheme for Network Protector Units in the Secondary Networks of Electric Power Distribution Grids

Milan Joshi, Mckayla Snow, Ali Bidram (), Matthew J. Reno and Joseph A. Azzolini
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Milan Joshi: Department of Electrical and Computer Engineering, University of New Mexico, Albuquerque, NM 87131, USA
Mckayla Snow: Department of Electrical and Computer Engineering, University of New Mexico, Albuquerque, NM 87131, USA
Ali Bidram: Department of Electrical and Computer Engineering, University of New Mexico, Albuquerque, NM 87131, USA
Matthew J. Reno: Electric Power Systems Research, Sandia National Laboratories, Albuquerque, NM 87123, USA
Joseph A. Azzolini: Electric Power Systems Research, Sandia National Laboratories, Albuquerque, NM 87123, USA

Energies, 2025, vol. 18, issue 17, 1-17

Abstract: Network protector units (NPUs) are crucial parts of the protection of secondary networks to effectively isolate faults occurring on the primary feeders. When a fault occurs on the primary feeder, there is a path of the fault current going through the service transformers that causes a negative flow of current on the NPU connected to the faulted feeder. Conventionally, NPUs rely on the direction of current with respect to the voltage to detect faults and make a correct trip decision. However, the conventional NPU logic does not allow the reverse power flow caused by distributed energy resources installed on secondary networks. The communication-assisted direct transfer trip logic for NPUs can be used to address this challenge. However, the communication-assisted scheme is exposed to some vulnerabilities arising from the disruption or corruption of the communicated data that can endanger the reliable operation of NPUs. This paper evaluates the impact of the malfunction of the communication system on the operation of communication-assisted NPU logic. To this end, the impact of packet modification and denial-of-service cyberattacks on the communication-assisted scheme are evaluated. The evaluation was performed using a hardware-in-the-loop (HIL) co-simulation testbed that includes both real-time power system and communication network digital simulators. This paper evaluates the impact of the cyberattacks for different fault scenarios and provides a list of recommendations to improve the reliability of communication-assisted NPU protection.

Keywords: direct transfer trip; network protector units; power system protection; secondary networks (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2025
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