Intrasubstation Communications Improved With Optical Interface Standard IEEE C37.94*

What Is IEEE C37.94?

IEEE C37.94 is the only standard providing plug-and-play transparent communications between different manufacturer’s teleprotection and multiplexer devices using multimode optical fiber. The standard defines clock recovery, jitter tolerances, physical connection method, and the equipment-failure actions for all communications link failures.

Why Use IEEE C37.94?

Historically, interface standards between teleprotection equipment and multiplexers were electrical only. Those high-speed (56-64 kbps), low-energy signal interfaces are vulnerable to intrasubstation electromagnetic and radiofrequency interference (EMI/RFI), signal ground loops, and ground potential rise, which considerably reduce the reliability of communications during electrical faults.

Today, the safest and most-reliable protection communications schemes in the industry dedicate optical fibers to intra-substation communications links between protection (digital relays) and telecommunications (multiplexers) devices. Optical fibers do not have ground paths, and are immune to noise interference, which eliminates data errors common to electrical connections.

The IEEE C37.94 standard allows implementation of any protocol because there are no restrictions to the content of the data stream. Indeed, any data streams can be sent as long as the physical and signal-timing requirements are met.

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*IEEE C37.94 Standard for N Times 64 Kilobit Per Second Optical Fiber Interfaces Between Teleprotection and Multiplexer Equipment (2002)