GOOSE between substations: TR 61850-90-1 and R-GOOSE

Short answer

Classic GOOSE is layer 2 multicast and does not cross a router, so it does not leave the substation network on its own. There are two ways to take it to another substation: extend layer 2 with a tunnel or an Ethernet service over the transport network, as IEC TR 61850-90-1 proposes, or use routable GOOSE (R-GOOSE), defined in IEC TR 61850-90-5 over UDP/IP, with authentication according to IEC 62351. It is used for transfer trips, interlocking between substations and remedial action schemes.

Why GOOSE does not leave the substation

GOOSE is the IEC 61850 event message between IEDs: positions, pickups, blocking signals and trips. It travels directly over Ethernet, with a destination multicast MAC address, a VLAN and an APPID, and no IP header. That is why it is fast, and for the same reason a router does not forward it: it has no IP address to route.

Inside the substation that is not a problem, because every IED shares the layer 2 network. But some applications need to take an event to another substation: a transfer trip, a blocking signal, an interlock between two neighboring substations or a remedial action scheme that acts on several of them. That requires one of two solutions.

Option 1: extend layer 2 between substations

The technical report IEC TR 61850-90-1, Use of IEC 61850 for the communication between substations (2010), covers information exchange between substations with IEC 61850, in particular for protection and interlocking. The most direct way to carry GOOSE is for the transport network to deliver a point-to-point or multipoint Ethernet service between the two substations, as if they were a single local network:

An Ethernet channel over the multiplexer and fiber network, with dedicated capacity.
A layer 2 service over a packet network (for example, a pseudowire over MPLS).
Direct fiber between the switches of the two substations, when the distance allows it.

The advantage is that the IEDs do not change: they publish and receive the same GOOSE. The cost is that the layer 2 domain grows, and with it the risk that a traffic storm or a VLAN error in one substation affects the other. The design strictly filters which VLANs and addresses cross the link.

Option 2: routable GOOSE (R-GOOSE)

The report IEC TR 61850-90-5 (2012) was written to transmit synchrophasors with IEC 61850 according to IEEE C37.118, but it also defined routable profiles for GOOSE and sampled value messages. Those profiles, known as R-GOOSE and R-SV, encapsulate the message in UDP over IP, with an IP multicast or unicast destination address. Because it carries an IP header, it can cross routers and routed networks between substations. The report itself notes that these routable packets can carry general IEC 61850 data, not just synchrophasors.

Path of an R-GOOSE message between substations

01IED in substation APublishes the event as R-GOOSE over UDP/IP, authenticated
02Edge routerRoutes the IP multicast to the transport network, with filtering
03Network between substationsLatency and availability guaranteed for the application
04Router in substation BDelivers the message only to the subscribers' network
05IED in substation BChecks the authentication and processes the event

Not every IED supports R-GOOSE. Before designing around this option, it is confirmed in each device’s conformance documentation (PICS and PIXIT) and with the manufacturer.

Security

A message that can trip a breaker and travels over a routed network has to be authenticated. The IEC 62351 series covers it in two parts:

IEC 62351-6 defines the protection of GOOSE and sampled value messages, with integrity and, when required, confidentiality.
IEC 62351-9 covers key management. For group communication such as GOOSE, it uses the IETF GDOI protocol, extended for IEC 62351 in RFC 8052. A key server delivers the group keys and their policy to publishers and subscribers.

In addition, the network between substations is separated from any corporate or public network, and the edge routers filter which addresses and ports get through. The general framework is in IEC 62351.

Applications

Transfer trip and teleprotection signals, as an alternative or complement to teleprotection equipment and classic teleprotection schemes. In practice, transfer trips still often go through teleprotection or over the 87L line differential channel, whose performance is proven.
Interlocking between substations, for example when a line disconnector depends on the state of the remote end.
Remedial action schemes, such as load shedding or generation tripping, which act on several substations based on a condition detected in another.
Synchrophasors, the original use of IEC TR 61850-90-5, together with the PMU and PDC synchrophasor network.

What the transport network must provide

Inside the substation, a trip GOOSE requires the most demanding transfer time class of IEC 61850-5. Between substations, the wide area network time adds to the IED time. The guideline IEC TR 61850-90-12 covers the engineering of those networks: topology, redundancy, latency and quality of service, traffic management and security. The time each application requires comes from the protection study and is checked on the real network, under normal conditions and on the backup route.

How to choose

How to take a GOOSE message to another substation

Do the IEDs at both ends support R-GOOSE with authentication?
- NoDedicated layer 2 service between substations with strict VLAN filtering, or conventional teleprotection
- YesIs the network between substations routed, and does it guarantee the application time?
  - YesR-GOOSE with key management and filtering edge routers
  - NoDedicated layer 2 service or conventional teleprotection

We help with your project

Tiza Group does the communications engineering between substations, including trip and interlocking GOOSE between high and extra-high voltage substations. Publication and subscription in the IEDs are configured through remote relay configuration. Contact us.

IEC 61850 GOOSE: how it works, stNum, sqNum and testing
Direct transfer trip (DTT)
Multiplexer and fiber optic network
IEC 62351: cybersecurity for IEC 61850, 104 and DNP3
GOOSE not arriving or arriving late
Teleprotection and 87L over IP/MPLS networks: what changes
WAN for substations: IEC TR 61850-90-12
Redundant teleprotection channels: routes and diversity
Substation communications by voltage level

References

IEC TR 61850-90-1:2010, Use of IEC 61850 for the communication between substations.
IEC TR 61850-90-5:2012, Use of IEC 61850 to transmit synchrophasor information according to IEEE C37.118.
IEC TR 61850-90-12:2020, Wide area network engineering guidelines.
IEC 62351-6:2020, Security for IEC 61850.
IEC 62351-9:2023, Cyber security key management for power system equipment.
IETF RFC 8052, Group Domain of Interpretation (GDOI) Protocol Support for IEC 62351 Security Services.

Frequently asked questions

What is the difference between GOOSE and R-GOOSE?

The content is the same kind of event message, but classic GOOSE travels directly over Ethernet with a multicast MAC address and does not cross routers, while R-GOOSE is encapsulated in UDP over IP with an IP multicast or unicast address, so it can cross a routed network between substations.

Does R-GOOSE replace teleprotection equipment?

Not necessarily. Transfer trips still often go through teleprotection equipment or the line differential channel, whose performance is proven. R-GOOSE makes sense when the network between substations guarantees the time and availability the application requires and both ends support it.

Is it safe to send a trip over an IP network?

Only if the message is authenticated and the network is designed for it. IEC 62351-6 defines the protection of GOOSE and sampled values, and IEC 62351-9 the management of group keys. In addition, the network between substations must be separated from any corporate or public network.