Implementation of modern interlocking and data acquisition in high voltage systems

Objective of the Standard IEC 61850

The international IEC 61850 standard sets frames for Substation Communications Networks and Systems. IEC 61850 consists of different parts ranging from the requirements on Substation Automation Systems to the details of a communication protocol.

The standard defines a wide set of protocol services for Substation Level Automation and an expandable object-oriented data model. It specifies how the functions expose their information to a Communication Network but not any protection or control functions.

XML description language is also defined for Substation Automation System. The purpose of the standard is to provide interoperability between the IEDs from different suppliers and the functions to be performed by systems for power utility automation but residing in physical devices from different suppliers.

GOOSE

In IEC 61850, Generic Object Oriented Substation Event is the main way to specific communication services mapping. GOOSE is a method of exchanging messages between IEDs over a local Ethernet network and it is suitable for time critical applications such as protection functions in a substation.

GOOSE connections replace transmission via contacts and binary inputs; for protection signals, transmission times under 10 ms are required and under 20 ms for switch positions and interlockings. Measured and metered values are transmitted in less than 100 ms.

Possible data functions are for example breaker tripping, status update, interlocking and event recording. A message send by an IED can be received and used by several receivers.

GOOSE is also supported between devices in different switchgears. The exchanged information is described in data terms via standard-confirming Substation Configuration description Language (SCL). The application layer in GOOSE is directly mapped to the data link layer, which means that the message is skipping intermediate layers including transport and network layers.

That is why GOOSE message involves no IP address and can be transmitted only via a LAN. The LAN as a solution reduces total costs and time in engineering because hardwired connections are not needed to make.

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