Power Systems Lab · 18 modules · all computed in your browser

IEC 61850 GOOSE / SV

GOOSE stNum/sqNum retransmission, process bus SV.

GOOSE publisher · retransmission timeline

An IED publishes a dataset, for example a trip (PTRC.Tr) or a breaker failure initiate, as a Layer-2 multicast GOOSE message. On a change it bursts quickly, then backs off to a heartbeat.

stNum (state changes)

sqNum (repeats)

Data value

false

Next gap

1000 ms

The subscriber checks timeAllowedToLive (often 2× the current gap). If no message arrives in time, it raises a GOOSE-failure alarm and the logic falls back.

t (ms)	stNum	sqNum	value	gap

Sampled Values (SV) · process bus

What: A merging unit samples the CT and VT secondaries in the yard and streams them as Ethernet multicast frames (IEC 61850-9-2). Copper CT and VT wiring to the relay panel is replaced by fibre.

Rate: The IEC 61869-9 preferred rate for protection is 4800 samples/s (80 per cycle at 60 Hz), with each frame carrying 4 currents + 4 voltages, smpCnt and a sync flag.

Time: Samples must be time-aligned, normally with PTP (IEC 61850-9-3 power utility profile of IEEE 1588). Losing sync is treated like losing CTs, so protection blocks.

Learn it

IEC 61850 is a data model plus communication services for substations. Logical nodes like PTOC (overcurrent), PDIS (distance), XCBR (breaker) and PTRC (trip conditioning) give every function a standard name. GOOSE replaces hard-wired peer-to-peer trip and interlock contacts with fast multicast messages. MMS carries SCADA and engineering traffic. SV replaces analog CT/VT wiring.

GOOSE has no acknowledgement, so reliability comes from repetition. A change bursts out at short intervals, and stNum and sqNum let the subscriber detect new states and lost frames.

Quiz · 0/3

1. On a GOOSE data change, which counter increments?
2. GOOSE is transported…
3. If the SV time sync is lost, a well-designed relay should…

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