GOOSE operates at Layer 2
GOOSE bypasses IP for less than 4 ms latency. GOOSE is unroutable. Keep GOOSE traffic within a single VLAN.
9.3 IEC 61850 and IEEE 1588
The previous chapter covered fieldbus systems and the transition to Industrial Ethernet. 2 international standards govern how industrial Ethernet networks communicate in infrastructure installations. IEC 61850 defines substation communication. IEEE 1588 delivers the precision timing that both IEC 61850 and PROFINET IRT depend on.
IEC 61850 — Substation Automation
Section titled “IEC 61850 — Substation Automation”IEC 61850 defines communication in electrical substations. The standard specifies the protocol, data model, configuration language, and testing methodology.
GOOSE — Generic Object Oriented Substation Event
Section titled “GOOSE — Generic Object Oriented Substation Event”GOOSE (Generic Object Oriented Substation Event) is the real-time messaging mechanism in IEC 61850. GOOSE trips circuit breakers and sends interlocking signals.
| Parameter | Value |
|---|---|
| Transport | Ethernet multicast (Layer 2, no IP) |
| EtherType | 0x88B8 |
| Latency requirement | < 4 ms (Class P1) |
| Retransmission | Yes, at increasing intervals |
GOOSE bypasses IP entirely for minimum latency. Like PROFINET RT, GOOSE is unroutable. Keep GOOSE traffic within a single VLAN.
Sampled Values (SV) carry digitized current and voltage measurements from Merging Units to protection relays. SV requires less than 1 ms latency. Both GOOSE and SV require network redundancy (HSR or PRP) and sub-microsecond time synchronization via IEEE 1588 PTP.
Hirschmann MACH series switches are certified for IEC 61850 applications.
IEEE 1588 — Precision Time Protocol
Section titled “IEEE 1588 — Precision Time Protocol”IEEE 1588 PTP (Precision Time Protocol) delivers sub-microsecond time synchronization across Ethernet networks. IEC 61850 Sampled Values, PROFINET IRT, and TSN require PTP.
| Term | Definition |
|---|---|
| Grandmaster Clock | The PTP master clock, typically GPS-synchronized. The Grandmaster Clock distributes time to the other devices. |
| Transparent Clock | A switch mode compensating for forwarding delay in PTP timestamps |
| Boundary Clock | A switch mode terminating PTP on 1 side and re-originating PTP on the other |
Hirschmann switches support IEEE 1588v2 PTP with hardware timestamping for sub-microsecond accuracy.
Key Takeaways
Section titled “Key Takeaways”PTP for time-sensitive applications
IEC 61850 SV and PROFINET IRT require sub-microsecond synchronization via IEEE 1588 PTP. NTP lacks the required accuracy.
What Comes Next
Section titled “What Comes Next”Standards define the rules. Topology defines the physical layout. The next chapter covers the network topologies used in OT environments: star, ring, daisy-chain, and hierarchical architectures, with guidance on when to use each.
References
Section titled “References”- IEC 61850-8-1:2011 — Communication networks and systems for power utility automation
- IEEE 1588-2019 — IEEE Standard for a Precision Clock Synchronization Protocol
- Mackiewicz, R. E. (2006). Overview of IEC 61850 and Benefits. IEEE PES T&D Conference.