Modern Digital Secondary Systems: How Sampled Values (SV) and TiDL Enable Protection and Control

#power #system #packet #isampledvalue

This seminar compares two Digital Secondary System (DSS) technologies for substation protection: IEC 61850 process-bus Sampled Values (SV) and point-to-point TiDL. It begins by motivating DSS adoption (reduced copper, improved safety, greater flexibility) and then asks how communication behaviors become protection behaviors. For SV, we review merging units, publisher–subscriber messaging, and the role of time (PTP) in aligning sampled currents and voltages. Using phasor-based distance protection as an example, we show how phasor extraction and impedance calculations
are sensitive to SV channel delay (MU processing plus network delay) and packet loss, compromising security and dependability.

The talk then consolidates mitigation strategies used in relays and settings: deterministic wait-time coordination, SV status-bit supervision of torque equations, limited-gap interpolation, and blocking/freezing vulnerable elements during data loss with a settling block after restoration. TiDL is presented as a contrasting architecture that uses direct fiber links between a field merging unit and relays, avoiding switched protection networks and external time for protection, simplifying commissioning and shrinking the attack surface, while trading off some interoperability and process-bus flexibility. We close with selection criteria for bay count and cost.

This technical talk will be delivered by Dr. Mohammad AAMIR RAHMANI, Ph.D (Development Lead Engineer, Protection Systems, R&D, SEL).