GSE (Generic Substation Events)

Generic substation Events (GSE) is a control model defined as per IEC 61850 which provides a fast and reliable mechanism of transferring event data over the complete substation networks. This provides facility to transfer the same event message to multiple physical devices using multicast / broadcast services. GSE control model is further subdivided into GOOSE (Generic Object Oriented Substation Events) and GSSE (Generic Substation State Events).

Generic Object Oriented Substation Events (GOOSE)

Generic Object Oriented Substation Events (GOOSE) is a control model mechanism in which any format of data (status or analog ) can be grouped into data set and transmitted within a time period of 4 milliseconds.The following mechanisms are used for speeding up the transmission and increase reliability.

*GOOSE data is directly embedded into Ethernet data packets and works on publisher-subscriber mechanism on multicast or broadcast MAC addresses.

*GOOSE also uses VLAN and priority tagging as per IEEE 802.1Q to have separate virtual network within the same physical network & setting high priority for the message.

*Enhanced Retransmission mechanisms - The same GOOSE message should be retransmitted with varying and increasing re-transmission intervals. A new event on any of the GOOSE dataset element will cancel the existing GOOSE retransmission message and state number available in GOOSE is used to identify between re-transmitting GOOSE messages and new GOOSE messages.

Generic Substation State Events (GSSE)

Generic Substation State Events (GSSE) is an extension of event transfer mechanism in UCA2.0. Only Status data can be exchanged through GSSE and it uses a status list (string of bits) rather than dataset used in GOOSE. GSSE message is transmitted over MMS based stack (base stack without using TCP/IP) which necessitates more time for transmission & processing in comparison with GOOSE messages.

Custom Substation Event Implementations

There are custom implementations for substation event transfer which deviates from the basic GOOSE or GSSE. Some of the major implementations are listed below.

*Fixed GOOSE - This is implemented in GE IEDs which makes use of the GSSE data format (list of bits) over the GOOSE protocol. This is said to be faster than GOOSE as it is using unstructured data for it's transmission in comparison with the structured data used by normal GOOSE.

*Mirrored Bits [ [http://www.selinc.com/flyers/MirroredBitsFlyr.pdf SEL Mirrored bit technology] .] - This scenario is used in SEL IEDs for fast transmission of data.It is a relay-to-relay communications technology that exchanges the status of eight internal logic points called MIRRORED BITS, encoded in a digital message, from one device to another. This is said to be much faster than GOOSE if the transmission required is point to point but is not much effective for communication among various devices.

ee also

*IEC61850
*Manufacturing Message Specification

References