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In a pcap from a digital substation attention usually goes to GOOSE, SV, MMS and PTP. But useful diagnostics often live lower — in the MAC addresses. The article explains what an OUI is and how MA-L, MA-M, MA-S and CID differ, how to guess a vendor from the first octets, why a shared Source MAC on two IEDs breaks MMS and triggers MAC flapping, and what a digital-substation engineer should check on a first pass over a pcap.
CIGRE's first dedicated framework for virtualised IEDs will not publish until Q1 2028 — but the vPAC pilots that have to align to it are being commissioned now. Its scope is already public, through the working group's Terms of Reference and a framework article refeatured in ELECTRA 345 (April 2026): what is mandatory, what is deliberately out of scope, and what every 2026 vPAC pilot should already be doing in response.
Top-down IEC 61850 engineering — formalized in TR IEC 61850-90-30:2025 and TR IEC 61850-7-6 (Ed. 2) — moves specification errors from commissioning to the design phase, before a single IED is selected or procured. This article explains the mechanics of the five-step process: what each step produces, what files are exchanged, and why the sequence achieves outcomes the conventional bottom-up approach cannot.