Why GOOSE Messaging is like Social Media for relays
GOOSE (Generic Object Oriented Substation Event) messaging is a subset of the communication standards defined in IEC61850. It is a very fast messaging system for sending binary (on/off) status signals. All of CEE’s new NP900 range of relays can use GOOSE messaging to communicate with each other or any other GOOSE-enabled device on a network. This protocol can only be used for sending messages between Intelligent Electronic Devices (IEDs) at the same level in the hierarchy; GOOSE messages cannot be used to communicate directly with a Supervisory Control And Data Acquisition (SCADA) system. If required, Aggregators can collect GOOSE messages and re-transmit to SCADA using a different communications protocol. 
Older, MODBUS communication loops relied on one device being designated as a “Master” to send messages to all other “Slave” devices in the loop. Like karaoke on a Saturday night, whoever is in control of the Microphone gets to transmit their own out-of-tune rendition of Bryan Adams’s “Summer of 69” to the audience until someone else takes over the mic. Similarly with a MODBUS loop, the Master could only send data and the Slaves could only receive; at least until the next device in the loop was designated the Master. Or someone else is allowed to sing.
Singing Relay
Goose Messages
GOOSE messages operate on a totally different principle. When one NP900 relay sends a GOOSE message, it is sent to all devices on the network simultaneously. All devices on the network can transmit (Publish) data all the time. In much the same way that Twitter limits users to messages of 280 characters or less, GOOSE datasets are limited to a maximum of 16 binary messages. For really attention-seeking relays, it is possible to transmit more than one GOOSE dataset to send even more messages (like having many social media accounts, all broadcasting at the same time).
However, data that has been published to the network will be ignored by all other devices unless they have been programmed as Subscribers to that data; much like Twitter followers. Unlike Twitter, Subscribers (followers) will only receive specific types of data from one Publisher. Much like a friend who is only interested in your relationship status but doesn’t care what you had for dinner. For a Subscriber to receive more data from a Publisher, it must be programmed to accept each data type individually.  

A Subscriber can accept data from many different Publishers, but again each data type from each publisher must be configured individually as a GOOSE input. So if a Subscriber wants to know Paris Hilton’s relationship status and Angelina Jolie’s relationship status, they must be configured as two different inputs for that Subscriber. But there’s a catch. In the same way that you can only read so many Tweets in one day, each IED can only be a subscriber to a maximum number of GOOSE inputs. For the NP900, this limit is 64 inputs; other IEDs will vary depending on how much memory they have available.  

GOOSE datasets (Tweets) are published to the network in short bursts and contain all the data types that Publisher has been configured to send. Each Publisher always sends its data in the same order within the dataset (Publisher1: relationship = single; dinner = pasta), but different Publishers can send data in a different order depending on how they have been configured (Publisher2: dinner = chips; relationship = divorced). Subscribers have to be configured correctly to look for the information they require in the right place within the dataset. Subscribers which have been programmed to look for a specified data type in the wrong part of a GOOSE dataset will generate an error (Subscriber: What? Publisher2’s dinner is divorced? ERROR).

For this reason it is very important to keep track of exactly what data is being sent by each device, and in what order. CEE’s NP900 relays offer a simple solution to this problem: Any GOOSE configuration information from one relay can be saved and exported to any other NP900 relay. This means that both relays can send the same information in the same order. The saved file can also be used by Subscriber devices to select the published data they wish to receive; these can be automatically configured as logical inputs to make configuration easier.  
Communicating Relays
GOOSE publishers send their data constantly, regardless of whether or not any of the data has changed. The time between repeat messages is the cycle time. GOOSE subscribers use this repeated message to determine if there has been any interruption in communications (if someone you are following on Twitter has fallen asleep). However, if any of the data does change the publisher IED will send the GOOSE dataset more frequently for a short time, before returning to the previous cycle time.

Technically, GOOSE messages cannot be used to issue instructions (“You must vote for the Constitutional Anarchist party”), they can only be used to share binary data and status updates. However, Subscribers may use information received via GOOSE messaging in their internal logic and operate accordingly (like deciding how to vote). Therefore, GOOSE messages can be used in inter-tripping schemes and interlocks. The difference is that unlike hard-wired signals the sending IED (publisher) sends a message to every IED on the network “I have detected short-circuit current”; it is the receiving IED (subscriber) which must be configured to interpret that message as “I need to trip”.
So, in summary: NP900 relays from CEE can not only use GOOSE messaging but can save, import and share their configuration settings in an efficient and user-friendly manner. GOOSE messaging is a very fast and efficient way of transferring data between IEDs such as protection relays and is therefore nothing like social media.