Risk Analysis of Transformer Differential Protection in Electrical Substation

252

2026-03-24

John Seiquera

15:30

Digital substations using the IEC 61850 standard rely on precise time synchronization for distributed protection functions such as transformer differential protection (ANSI 87T). This thesis examines how time-synchronization attacks, particularly GNSS spoofing, affect system security on a commercial timing server in a substation test bed. Experiments show that remotely altering the time reference misaligns sampled values across merging units and causes transformer differential protection to malfunction, all without needing direct access to the network. Tests with different vendors’ merging units and relays show that certain timing disruptions can cause false trips, while some interoperability features give partial protection. Overall, the findings reveal a significant attack surface in digital substation architectures, emphasize the need to consider physical threats, and propose practical measures to strengthen IEC 61850-based protection schemes against timing attacks.