Transformer protective relays outside in weatherproof box - good idea? 1

[bdn2004]

We are installing a new SCADA at our plant. We've run into an issue that is more about constructability than anything. At present all of the alarm signals off the transformer's instrumentation: pressures, temps, levels are parallelled together to create only one signal. With the SCADA we want all of them individually. This seemed easy enough to do just run additional wires out there. The trouble is the conduit going out there is stuffed full, and putting another conduit in, although we can do it will be very costly, time consuming and other reasons to think about an alternative. I attached a sketch showing the issue.

One idea I had was to put the relays in an outdoor box and re-use the existing conduit to the new SCADA. This would put the largest wires in the conduit outside only and free up space for the signal wires back to the SCADA plc. We don't have any protective relays in outdoor enclosures now in the entire plant. Is this ever done? Does anyone have a better idea here?

Also this isn't just one transformer it's about 40 of them.

 

[PHovnanian]

You might want to talk to a SCADA/PLC wizard and see if they have some sort of multiplexing solution available. Combine all the alarm signals and return them to the control house on the one pair now used for combined alarm. There are systems that can use the one pair for power going out to the PLC as well as bidirectional data. Power Over Ethernet being one example.

I've seen outdoor relay installations and they work well as long as the enclosure is adequate for the environmental conditions. This includes ambient temperature concerns, which might require heat in the enclosure.

The other thing to consider is that, returning all your CT wiring to a central location might be a requirement for differential bus protection schemes. If this is the case, moving relays out to transformers, breakers, etc. might not save you much wiring in your conduit.

 

[DTR2011]

how about a fiber optic solution like the SEL 2505?

 

[Bramb]

You'd better ask to the SCADA supplier to have a remotable DI device (distributed I/O) that can be installed in the transformer junction box, wired to your alarms and then connected to SCADA via FO (better than copper (Ethernet or RS485) to avoid EMC disturbances).

Ciao
Erminio

The difference between overload and short circuit lies in the nature of the fault, not in the value of the current.

 

[vandal06]

Echoing what smallgreek suggested; we've used the 2505 multiple times for this very same application.