GOOSE

Basics

The service GOOSE (generic object-oriented substation event) is, next to the Sample Values (SMV), the enabler for the process bus, that is the communication with the devices in the process level. Its key characteristic is a reliable communication within milliseconds with little payload. Typical data are:

trip command of protection function to the circuit breaker
position of switchgear devices to bay control units
interlocking information (position of switchgear between bay’s)

The GOOSE is mapped to the Ethernet packet “only“, which means there is no Transmission Control Protocol (TCP) or Internet Protocol (IP) it is utilizing. With that there are three important implication:

No IP: GOOSE does not allow for one-to-one association. (except R-GOOSE) Instead, GOOSE is utilizing the Ethernet multicast
No TCP: GOOSE publisher (sending IED) and GOOSE subscriber (receiving IED) are completely decoupled. There is no mechanism that allow to resend a GOOSE on a receiving IEDs request. to compensate for that, GOOSE has a so-called repetition strategy.
No TCP: The GOOSE payload is limited to an Ethernet frame.

Ethernet multicasting

Instead of utilizing the IP protocol to define the destination, GOOSE is utilizing the Ethernet multicasting. Any IED that is connected to the same switch as the sending IED is receiving the GOOSE packet and then can decide to use this information or drop it. It is doing so by fixing the destination MAC-address range to 01-0C-CD-01-00 to 01-0C-CD-01-1F-FF. With a destination address starting with 01 defining the multicast range.

Repetition Strategy

The main requirement of a GOOSE is speed. As such, a GOOSE packed is issue every time there is a change in its data set. In addition to those packets - triggered by changed data sets - there are GOOSE packets that are issued a part of the repetition strategy.

Right after the packed triggered by a data change, a repetition packet is issue. The time delay between these packets is called the minimum repetition interval. The time interval is in the range of milliseconds and is designed to still be fast enough in case the first packet fails to be transmitted. The time delay with the coming repetition packets increases over time and ultimately reaches the maximum repetition interval. Typical numbers for the maximum repetition time is in seconds, 1-10s. The idea behind this time is a monitoring of the GOOSE. Just imaging the GOOSE holds the trip signal of overcurrent protection and there is no trip for say 10 years. How would the receiving IED know that the GOOSE publisher is still online. You might say the GOOSE service has an in build wire break protection. Linked to the maximum repetition interval is the time allowed to live, which is recommended to be twice the maximum repetition interval.

GOOSE control block (GCB)

The service GOOSE can be found in the data model of the IED. It is represented there with a very specific data object called GCB. GOOSE control block can only be allocated in the logical node LLN0. A GOOSE control block is like a data object, structured data. Instead of data attributes, the control block hold configuration setting for the GOOSE such as:

GoCBName: the name of the GCB
GoCBRef: the reference of the GCB in the data model
GoEna: whether the GOOSE is active
GoID: the GOOSE ID
DataSet: the reference to the data set
ConfRef: an integer number indicating changes in the GOOSE data set
NdsCom: whether the GOOSE still to be commissioned
DstAddress: the destination MAC-address of the GOOSE

The GOOSE control block can be configured through an SCL file. There the GOOSE control block is represended with the element GSEControl

R-GOOSE

The R-GOOSE stand for routeble GOOSE. This fairly new type of GOOSE is utilizing the IP protocol. With that, a GOOSE can be routed through the wide area network. It is mainly used to communicated between two substations where both of the substation are separate LAN connected through WAN. Typical examples are permissive overreach transfer trip (POTT) or permissive underreaching transfer trip (PUTT) protection schemes.