Phase monitor?

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kbsparky

kbsparky

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Location
Delmarva, USA
We are dealing with a radio station transmitter site that has been having some issues with phase or power loss.

They have requested that we install a phase loss device that monitors the incoming power ☼ahead☼ of the main breaker. That way, if the power company loses one or more phases, they can notify them quicker. In this case, we are dealing with a 3-pole 200 Amp breaker, mounted in its own NEMA-1 enclosure. The meter box is directly behind the enclosure, on the outside of the building. The system is 208Y/120 Volts.

How have you handled phase loss monitors placed ahead of the main breaker? I can imagine some sort of inline fuse protection would be needed on such a setup, and a separate enclosure for auxillary equipment.
 
Just curious...is that main breaker tripping occasionally? I maintain a radio transmitter site with a similar main breaker configuration, except it's a 120/240 open delta (yecch).
 
pwh152 said:
what is the purpose for having it ahead of the main? if you lose a phase it will affect the entire system
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Of course it does. So, if the main trips out, someone has to travel to the normally unmanned transmitter building and reset it. IF the POCO loses one or more phases, the station still goes off the air, but traveling to the site is a waste of time. Calling the POCO is the correct remedy. But time is of the essence here, and waiting until someone actually gets to the transmitter only to find out they have to call the POCO is a real waste of time.

A line-side phase monitor would let them know whether it was the POCO that lost it, or not. This would save them precious time. Dead air time is disastrous when dealing with radio station protocols.
 
masterinbama said:
I have built my own with an enclosure a piece of DIN rail the relay and one of these.

http://ab.rockwellautomation.com/Circuit-and-Load-Protection/Circuit-Breakers/1489-Circuit-Breaker
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That would very likely be an issue with a service tap and available fault current.

Available Short Circuit Current
The Bulletin 1489-A circuit breakers should only be applied in those
applications in which the available short-circuit (or fault) current is
less than or equal to 10 kA...14 kA (US/Canada) and 15 kA (IEC).
Click to expand...
 
ptonsparky said:
I don't maintain a radio sight, but I have very few customers that would put up with a main tripping periodically.
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And in my case, there's a backup genny to kick in, so the off-air time is only 30 seconds. This radio station will drive out to check the genny during the time it's on, and will check the main to see if it's tripped. Happens a couple of times a year, when there's a phase loss. They're at the end of a long rural run.

Could some CT's installed before the main be used to build up a phase monitor without actually tapping it?
 
Why not just install a main circuit breaker with an auxillary switch, and then install the phase monitor on the load side?
 
kbsparky said:
We are dealing with a radio station transmitter site that has been having some issues with phase or power loss.

They have requested that we install a phase loss device that monitors the incoming power... we are dealing with a 3-pole 200 Amp breaker 208Y/120 Volts.
Click to expand...

I have no helpful suggestions, but I am very curious- Why is there three phase at this radio transmission tower?

I have not worked on a lot of radio/cell sites, but I have worked on a dozen or so and they have all been single phase.
 
steve66 said:
Why not just install a main circuit breaker with an auxillary switch, and then install the phase monitor on the load side?
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Intriguing idea. The breaker is a Square D QDL32200. Do they have an aux switch accessory for this breaker? I'll have to look into this possibility ....

Edit to add: The Square D Digest shows that an aux switch accessory is NOT available for this breaker .... :weeping:
 
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Our utility has provided power quality / phase loss device at the plant I work at. Maybe they would be willing to do it, or supply it if not to expensive.
 
iwire said:
That would very likely be an issue with a service tap and available fault current.
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What if the phase monitor had its own disconnect and OCP?? Would that make it legal? The phase monitor OCP wouldn't be likely to trip since it only feeds the phase monitor.


kbsparky said:
Intriguing idea. The breaker is a Square D QDL32200. Do they have an aux switch accessory for this breaker? I'll have to look into this possibility ....

Edit to add: The Square D Digest shows that an aux switch accessory is NOT available for this breaker .... :weeping:
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Bad luck. But could you replace the entire breaker?


ActionDave said:
Interesting. I have never seen such a critter.
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Cell phone sites are normally very low power. They have a very small range, and digial encoding reduces the necessary power. (Think about how little power a handheld cell phone puts out from its battery. The cell phone tower doesn't need to put out much more power than the cell phone.)

On the other hand, if this is an AM or FM broadcast station, they have a lot more range and are may put out 100KW or more. Makes 3 phase a lot more useful.
 
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