T&D World Magazine

Safely Extend EIA-485 Networks Via Fiber-Optic Links

Schweitzer Engineering Laboratories, Inc. has announced the SEL-2820 Fiber-Optic V-Pin Transceiver is now available for purchase with a list price of $150. This transceiver allows instrumentation and control professionals to safely add isolated segments to multidrop and point-to-point EIA-485 networks separated by up to 500 meters. Also, connecting segments with optical fiber instead of copper wire improves safety, signal integrity, and reliability.

The SEL-2820 is easy to integrate. The control dual in-line package (DIP) switches can be set for two-wire or four-wire, multidrop or point-to-point operation, and to control transmitter keying. The transceiver operates over a ¨C40¡ã to +85¡ãC temperature range and meets or surpasses electric utility and industrial type-test standards for instrumentation, control, and communications equipment.

Add segments to EIA-485 networks by inserting an SEL-2820 into an existing network, and connect it via fiber-optic cable to an SEL-2820 that serves as the master connection point for the new segment. SEL-2820 optics are compatible with SEL-2800 Fiber-Optic Transceivers. An SEL-2800 can be plugged into the EIA-232 port of a master or remote device and connected via optical fiber to an SEL-2820 that is in turn connected to an EIA-485 network.

Many industrial, commercial, and electric power applications deploy low-cost multidrop EIA-485 serial networks, and it is valuable to extend these networks with fiber-optic transceivers. Engineering supervisor for the SEL offices in Vacaville, California, Rick VanHatten cites the example of photovoltaic (PV) solar power plants that use multiple arrays of solar cells, each connected to an inverter with controllers.

"A common physical design of the PV arrays results in inverters spaced 500 feet apart in a grid pattern," VanHatten said. "The instrumentation and controls for some inverters use EIA485 interfaces, but for safety and signal integrity, it is desirable to connect the inverters using optical fiber."

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