The four Keep-alives in IEC 61850

IEC 61850 uses several mechanisms to monitor the communication between two devices (Client/Server) or between a publisher and many subscribers and to monitor functions – in order to increase the overall reliability of the information exchange.

The four mechanisms allow to check connected devices and determine whether the connection and the devices are still up and running or not. Reactions on failures are a local matter of applications.

The two mechanisms for Client/Server are:

• Keep-alive in TCP connections (used by MMS) [RFC 1122]
• Reporting of Report Control Block attribute “IntgPd” [ACSI, 7-2]

The two mechanisms for Publisher/Subscriber (Layer 2 multicast) are:

• Time-Allowed-to-Live in GOOSE messages (next message in) [8-1]
• Sample Rate in SMV message (sampled measured value) [ACSI,7-2]

The following figure shows how Integrity Period (communicated in a Report message) could be used to cyclically inform the client that the Reporting mechanism is up and running. Integrity Period is often used in cases where events happen very seldom and where the client wants to have a “heart beat” from the reporting server.

The configuration of the DataSet and the Report Control Block is usually provided by a SCL file. In the case of SystemCorp’s IEC 61850 API it is easily be done by uploading the corresponding SCL File to the IED, e.g., the Beck IPC IEC61850@CHIP.

Click HERE to evaluate the “Keep-Alives” with Reporting and GOOSE and real software running under Windows.

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