Annunciator Circuit 1

[mls1]

We're involved in the replacement of an annunciator system in a large powerhouse. The existing system is 125VDC and the new system is to be 24VDC. For the most part this shouldn't be an issue but a remote lightbox system in the control room is as far as 1600 feet from the field annunciators. The existing wire is 16 gage and the lightbox switching current should not exceed 0.08A or so. A common return may have enough voltage drop to be a concern but I think that could be managed. My concern is induced potentials (granted they will be AC) and cable capacitance. I've seen phantom ground currents and induced voltages high enough to set off a tick tracer in this powerhouse. Is there any hard guidance for using 24VDC control circuits in lengths over 1000'? Are my concerns warranted?

 

[pwrtran]

Don't know your system, but can you run 120VAC as a medium to some dry contacts in the lightbox for annunciation?

 

[davidbeach]

Use a smart annunciator and run power and a signal cable.

 

[rterickson]

Schweitzer makes a nice one:

https://www.selinc.com/SEL-2523/?v=2