IEEE C37.94 Optical Interface Standard
What Is IEEE C37.94?
IEEE C37.94 is the only standard providing plug-and-play transparent communications between different manufacturers’ 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 radio frequency 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 intrasubstation 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.
SEL Products
- SEL-3094 Interface Converter
The SEL-3094 Interface Converter converts electrical teleprotection interfaces to the IEEE C37.94 optical standard. Connect an SEL-3094 to an ITU-T G.703, EIA-422, EIA-485, or EIA-232 device, and use up to 2 km of optical fiber to link to a C37.94 multiplexer.
- SEL-2126 Fiber-Optic Transfer Switch
Switches fiber-optic links to maintain line current-differential (87L) and communications-assisted (POTT, DCB) pilot tripping schemes during bypass operations.
- SEL-2894 Interface Converter
The SEL-2894 Interface Converter converts EIA-232 links to IEEE C37.94 fiber-optic links.
- SEL-311L Line Current Differential Protection and Automation System
Use the SEL-311L Line Current Differential System with integral, four-zone distance backup for easy-to-apply, high-speed line protection.
- SEL-2594 Contact Transfer Module
The SEL-2594 Contact Transfer Module provides secure, high-speed contact transfer through communications multiplexers, using IEEE C37.94 Standard fiber-optic interface.
- SEL-2595 Teleprotection Terminal
The SEL-2595 Teleprotection Terminal provides secure, high-speed pilot protection through communications multiplexers, using IEEE C37.94 Standard fiber-optic interface.