GOOSE data is transmitted event based and at regular intervals in 802.1Q multicast frames over Network1. Peer devices can determine the state of the communications by listening for the transmissions. When a data value changes, the GOOSE message with the latest data values is transmitted multiple times for a few milliseconds to ensure the reception of the changed data. After fast retransmission, the GOOSE retransmission scheme moves to use the heartbeat cycle time.
In GOOSE, data sending is based on data sets and GOOSE control blocks. The data set defines what device data is used in the GOOSE service and sent to the local Ethernet subnetwork in a GOOSE message.
| GoCB property | Description |
|---|---|
| GoCB name | GOOSE control block name |
| Application ID | A unique GOOSE identification string for each GoCB in the system. By default, it is the GoCB identification in the relay data model. |
| Max Time | Indicates the background "heartbeat" cycle time in milliseconds; the default value is “10 000 ms”. If there are no data changes, the relay still resends the last message content with the heartbeat cycle. Communication supervision is based on this idle sending mechanism. |
| Min Time | Indicates the maximum response time to data changes in milliseconds. In the relay, the value is always "10ms" for sent data. |
| Multicast MAC address | A multicast addressing scheme is used when sending GOOSE messages. A multicast address can be shared by several GoCBs but to enable the multicast message filtering of the devices and a properly working network, it is recommended to use unique multicast addresses in each GoCB. The multicast MAC address is the address to which the GOOSE data is sent. The receiving relay filters the frames and starts to process them if a multicast address is subscribed in the configuration. The range for GOOSE multicast addresses is 01-0CCD- 01-00-00...01-0C-CD-01-01-FF. |
| Configuration Revision | Integer value indicating the revision of the GOOSE configuration. It is sent in every GOOSE message. The integer indicates the number of changes in the sent GOOSE data set; the receiver checks the value to detect possible configuration mismatches. Both the GOOSE sender and the receiver must use the same ConfRev value from configuration. This ensures that both devices have the same configuration level in the substation configuration. ConfRev updates are done automatically by tools. If the latest system configuration is not downloaded to all required devices, the configuration revision may differ between the receiver and sender and data exchange does not work. |
| APPID | A hexadecimal application identifier value for the published GoCB. It needs to be a unique value within the system. It identifies the purpose of a data set. The value range is 0000...3FFF. |
| Data set | Data content sent in GOOSE messages |
| VLAN ID | The VLAN group can be used when configuring the Ethernet network topology's virtual LANs for routing and segmenting. Configuration is done in managed Ethernet switches. If static VLAN identifiers are defined, it also affects the switch port configuration. Value “000” indicates a nonconfigured VLAN; in this case, switches do not filter these messages on a port basis. This is recommended if there is no need to split the logical network. The VLAN identifier is a three-character hexadecimal value with range 000...FFF. |
| VLAN Priority | Used in networks supporting VLANs. The priority is used with network switches. The default value for GOOSE is “4” and the value range is 0...7. |