Converting from Fiber to...

[jfpe]

I'm working on a job where the utility wants the ability to remotely turn off two solar inverters remotely. The utility will run fiber to the inverters. I don't know what communications protocol they will use.

The question I have is how to convert from a signal on fiber to the trip signal the inverter will accept. The inverters are from different manufactures and accept different inputs

Inverter #1 - Trips based on the opening of a normally closed dry contact

Inverter #2 - Trips based on a Modbus command given over Modbus RS-485.

I don't have a communication background, so I would appreciate any insight on what kind of device is needed to get from fiber optic cable to the trip signal the inverters can read. I expect we'll be pulling in a consultant on this, but I'd at least like to get a little background myself first.

Thanks,
jfpe

 

[VEBill]

It might be best to insert a rugged and reliable controller (PC?) in-between the fiber and the inverter controllers. Then you use the fiber to provide an Ethernet link back to headquarters, and the local side (discreet and RS-485) becomes very straightforward. This approach is very simple to source components, but adds the controller.

If you try to omit the controller, then you need to find fiber to discreet and fiber to RS-485 converters. Companies such as BlackBox sell into this market.

 

[JG2828]

It really depends on what is at the other end of the fiber. There are many manufacturers. For the 485/fiber one you could use either of these.

http://www.ruggedcom.com/products/ruggedmc/rmc20/

http://www.garrettcom.com/links_serial_485.htm

For the contact closure you could use the SEL2505 at both ends or RLH cards at both ends

http://www.selinc.com/SEL-2505/

http://fiberopticlink.com/Products/4RU_FiberOpticLinks/4WireDataEM.html

 

[amurray]

I agree it depends a lot on what the utility has at the other end. Do they also want other data (connection status, readings, alarms) If they require other communications data then this would be easily accomplished using a data concentrator, RTU or PLC. These devices typically have several comm. ports with different connections available (fiber, RS-485, RS-232) as well as hard wired inputs and outputs.

A couple of products - SEL 2440, SEL 2032, Control Microsystems SCADAPack 32P, Novatech Orion

Hope that helps.

Andy

 

[Prowler6484]

There are several fiber to serial media converters similar to what amurray mentioned. The dry contact I/O could be difficult to pass over the fiber optic cable without adding alot of equipment. For instance you could put a small channel bank at both ends, collect the RS485 and contact information at both ends, and utilize the fiber for a working and protect paths, this is assuming the inverters are in the same location. I've used a Loop Telecom channel bank for this very application. An easier way would be to use wireless devices, Banner Engineering and B&B Electronics make several that could be used here; again this depends on the distances involved. Either way it's not a complicated problem, it just depends on the real estate (is there space for a channel bank?) and facilties (Voltages present? Environmental issues?) available at each end.