GOOSE
Generic Object Oriented Substation Event — IEC 61850's publish/subscribe peer-to-peer Ethernet messaging service for fast event signalling between IEDs, with a 3 ms transfer-time budget for trip messages.
Also: Generic Object Oriented Substation Event, trip GOOSE
GOOSE is the publish/subscribe peer-to-peer messaging service in IEC 61850, mapped to Ethernet by IEC 61850-8-1. Any dataset — status, analogue value, quality flags — is grouped and multicast on the substation LAN. A retransmission scheme shortens the interval after a state change and lengthens it back to a heartbeat when quiescent.
The 3 ms budget
IEC 61850-5 defines performance classes. The stringent class is Type 1A (Trip) — transfer time ≤ 3 ms, measured end-to-end from the sending IED’s stack to the receiving IED’s. Type 1B (other fast messages) and Types 2/3 (slower) have progressively relaxed budgets.
The “four milliseconds” figure sometimes cited colloquially is a quarter-cycle at 60 Hz (4.17 ms) — a reference value, not the standard’s protection requirement.
Where it runs
Traditionally on the station bus, but also appears on process-bus LANs — for example, when a centralised protection function sends a trip command to a breaker IED. Carried as a layer-2 multicast frame: there is no TCP, no handshake, no per-pair session. Broadcast and forget.
Why TLS doesn’t fit
The latency budget rules out TLS — there is no session to handshake into and no time for asymmetric crypto on the receive path. IEC 62351-6 addresses this by embedding an HMAC or signature field inside the GOOSE PDU itself.
Typical redundancy pattern
Trip GOOSE almost always runs on a PRP network — duplicated frames over two parallel LANs, zero packet-loss on a LAN failure. The combination of GOOSE’s retransmission scheme and PRP’s frame duplication is what gets the protection scheme to a per-frame reliability the operator can defend.