ARAMCO requires very difficult two things to meet.
1. The maximum voltage drop shall not exceed 5%.
2. If a discrete loop length exceeds 305 meters (≈1000 feet), 120 VAC signal shall not be used due to potential capacitive (phantom voltage) or inductive coupling. In such cases, DC voltage shall be used.
Instrument are usually 24DC powered circuit with max 12AWG cable.(but normally max 14AWG, 12AWG is unusual case for us)
Some instrument power consumption 30~40W with 600~1000m. (Horn & Beacon for Gas detectors)
With these condition, 24VDC power is impossible to meet above requirement. (even manufacturer's allowable working voltage 20~27VDC cannot meet)
I think 120VAC signal to be used.
1. Anybody has experience for these things?
2. How to avoid potential capacitive or inductive coupling?
3. Phantom voltage can make work horn & beacon which has 30~40w?