SCADA — IEC 61850-5 §13.7

IEC 61850 <span>GOOSE</span> Latency

End-to-end budget per IEC 61850-5 §13.7 · PRP/HSR redundancy · Fiber link budget · Bandwidth check

IEC 61850 Substation Bay-Level LAN Topology — Path Analysis
IED Publisher t_pa = 1 ms Switch A 7–12 µs managed Single-mode fiber 5 µs/km Switch B 7–12 µs managed IED Subscriber t_tb = 1 ms t_total vs budget Type 1A ≤3 ms
Network Configuration
Type 1A = ≤3 ms (trip protection), 1B = ≤10 ms, 2 = ≤100 ms, 3 = ≤500 ms. IEC 61850-5:2013 §13.7.2.
PRP and HSR provide zero recovery time per IEC 62439-3. RSTP recovery 50–200 ms.
nodes
Worst-case path traverses N/2 nodes. IEC 62439-3:2021 §5.
hops
Number of managed Ethernet switches in the worst-case GOOSE path.
Cut-through switches have lower latency. Verify mode in switch configuration.
1 Gbps standard for protection LAN (IEC 61850-90-4 recommendation).
km
Single-mode fiber propagation: 5 µs/km at speed of light in glass.
Fiber Link Budget
dBm
Typical SFP: −8 dBm. Check vendor datasheet.
dBm
Typical SFP: −25 dBm. Check vendor datasheet.
pairs
0.5 dB per mated connector pair (LC, SC). Standard duplex LC = 2 pairs.
dB
Typical fusion splice: 0.1 dB. Mechanical splice: 0.3 dB.
dB/km
@ 1310 nm, OS2 single-mode: 0.35 dB/km typical.
Bandwidth
Per IED. Each dataset bursts ~12.8 kbps in first 4 ms retransmission sequence.
IEC 61869 9-2LE: ~38 Mbps per MU at 80 samples, 4 kHz.

Results

—
Latency Budget — IEC 61850-5 §13.7
Budget (Type)—
t_pa — Publisher processing—
t_pn — Switch hops (× hop delay)—
t_ta — Fiber propagation—
t_tb — Subscriber processing—
t_total — Total end-to-end —
Margin —
Redundancy — IEC 62439-3
Topology—
Recovery time—
Fiber Link Budget
Power available—
Connector loss—
Splice loss—
Fiber attenuation—
Link margin —
3 dB minimum required
Bandwidth Utilisation
GOOSE burst load—
Sampled Value load—
Utilisation —
≤ 60% recommended (IEC 61850-90-4)
Standards References
FAQ
IEC 61850-5:2013 §13.7.2 defines Type 1A as ≤3 ms end-to-end for protection-class GOOSE messages. The budget is split across publisher processing (t_pa), network propagation (t_pn), fiber delay (t_ta), and subscriber processing (t_tb).
PRP (Parallel Redundancy Protocol, IEC 62439-3 §4) uses dual parallel LANs — zero recovery time, works with any star/tree topology, doubles bandwidth. HSR (High-availability Seamless Ring, IEC 62439-3 §5) uses a single ring — zero recovery time, lower cost, but worst-case hop count is N/2. Both are suitable for Type 1A. RSTP (50–200 ms recovery) fails Type 1A and 1B budgets and must not be used for trip-critical functions.
A minimum 3 dB operating margin is required to account for fiber degradation, connector wear, and repair splices over the 25-year substation lifetime. Budget: Tx power − Rx sensitivity − connector loss − splice loss − fiber attenuation (0.35 dB/km at 1310 nm OS2).
Each GOOSE dataset retransmits in the first 4 ms after a state change: 1 + 1 + 2 + 4 = 8 frames × ~200 bytes = ~12.8 kbps burst per dataset. Sampled Values (IEC 61869 9-2LE) use 80 samples per cycle × 4 kHz × ~150 bytes ≈ 38 Mbps per merging unit. IEC 61850-90-4 recommends keeping total LAN utilisation below 60%.
132 kV outdoor AIS: star topology with managed 1 Gbps switches per bay, HSR or PRP backbone between process and station bus. 400 kV GIS: process bus with IEDs directly on HSR ring. Distribution substation: radial or ring, often RSTP on non-protection VLANs.
IEC 61850-5:2013 §13.7 defines GOOSE performance requirements. IEC 61850-90-4:2020 is the network engineering guideline (worked examples). IEC 62439-3:2021 covers PRP and HSR protocols. IEEE 802.1Q VLANs are assumed for traffic segregation between protection and process data.