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 Post subject: Airfield Constant Current Regulators
PostPosted: Wed Nov 06, 2019 9:55 am 

Joined: Wed Nov 06, 2019 9:41 am
Posts: 3
Location: Calgary AB
Hello everyone, I am the Electrical Coordinator, Airfield at The Calgary International Airport and I'm looking forward to learning new info and being in the group.

I have a question about our constant current regulators that power up the airfield lighting. It is an ungrounded series cct that has a constant current of 6.6 amps with a variable voltage determined by load and length of the run. The maximum voltage before the CCR trips is 3800 volts and max current of 6.9 amps if the primary wire is opened, this is not sustained and will trip within a second or two.
Off the top of your head, is this enough energy to create an arc flash? I am aware of the shock hazard and we do not ever work on this stuff live but I was curious because during construction, we have had the primaries cut by equipment.
Thanks for any info.

Tim


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 Post subject: Re: Airfield Constant Current Regulators
PostPosted: Mon Nov 18, 2019 7:52 am 
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Joined: Tue Jan 19, 2010 2:35 pm
Posts: 144
I did the arc flash study for the airport here where I live. I did include the connected loads to the runway lighting - these were fed by fused disconnect switches which then fed into the lighting controls. I don't believe there is enough power at the actual runway lights (I think that's what you are asking about) to cause any kind of sizeable arc flash. At least nothing that would create more than 1.2 Cal/sq centimeter.


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 Post subject: Re: Airfield Constant Current Regulators
PostPosted: Mon Nov 18, 2019 8:15 am 

Joined: Thu Jan 13, 2011 10:08 am
Posts: 12
Location: Orlando
Welcome to the airfield lighting business! A word of caution to people new to airfield lighting. An airfield lighting series circuit complies with all the laws of physics. However, a current loop behaves very differently from our typical voltage distribution systems.
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An airfield lighting series circuit is a current loop; thus, on the output of a constant current regulator (CCR), a short circuit is good, and an open circuit is bad. On a fully loaded 6.6-amp 30 kW CCR normal operating voltage will be approximately 4,545 volts, with the open circuit voltage approaching more than 9,000 volts. A CCR is designed to maintain a fixed current through the load by varying the output voltage. It is an ungrounded system; therefore, a single ground will have no impact on system operation. Two or more grounds will provide a parallel path for current and will likely impact the lumen output of the light fixtures between the two grounds. The CCR is designed to maintain this desired current flow, the CCR does not care if the load is a group of lamps or a person. The shock hazard on the secondary of a CCR is very real. Since short circuiting the output of a CCR is an accepted method of verifying proper CCR operation, in my humble opinion there is no arc-flash hazard on the output of the CCR. The operating characteristics of a CCR can be found in FAA Advisory Circular 150/5345-10H, Specification for Constant Current Regulators and Regulator Monitors available at www.faa.gov.
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Arc-Flash hazards and shock hazards are real issues on the input side of a CCR. The incoming AC power to the CCR presents the same characteristics as with other electrical equipment. The branch circuit feeding the CCR is typically far enough downstream from the source that the incident energy is low although not negligible. Each installation should be individually evaluated. Since both output and input may be closely adjacent in the CCR arc-flash hazards and shock hazards are both present within the CCR.


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 Post subject: Re: Airfield Constant Current Regulators
PostPosted: Tue Nov 19, 2019 8:27 am 

Joined: Wed Nov 06, 2019 9:41 am
Posts: 3
Location: Calgary AB
Thank you for the info, I'm looking forward to reading the FAA Circular.
I have been on the field for 19 yrs and we used to pull the secondary to isolate a sign or light when working on them, hence the original question. Our newest safety standard does not allow us to do this any more and the time frame to make repairs has gone through the roof.
A new Canadian Standard came into effect late last year and all electricians working on any airfield circuits fed from a CCR need to be certified.,I got mine earlier this year.
A bit of a note, in Canada other then some military installations, our biggest CCR is 20KW, 6.6 Amps.

Thanks.

Tim.


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 Post subject: Re: Airfield Constant Current Regulators
PostPosted: Wed Nov 20, 2019 7:14 am 

Joined: Thu Jan 13, 2011 10:08 am
Posts: 12
Location: Orlando
Good Morning Tim,
I am interested in the "certifying authority". We do not have an official airfield lighting certifying authority in the states. Generally the AHJ seem to accept the AAAE (American Assoc of Airport Exec) ACE (airport certified employee) program as a universal qualification. What can you tell me about the Canadian Certification process?
We are still trying to convince everyone (from management to the electrician) the circuit must be in an "electrically safe work condition" prior to changing lamps. The enhanced safety is worth the effort.
Thanks,
Carl


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 Post subject: Re: Airfield Constant Current Regulators
PostPosted: Wed Nov 20, 2019 2:11 pm 

Joined: Wed Nov 06, 2019 9:41 am
Posts: 3
Location: Calgary AB
Hi Carl, would you mind sending me an email and it will be easier to send you some info and maybe even chat.

<removed personal contact info>
Thanks.


Last edited by wbd on Fri Nov 22, 2019 6:48 am, edited 1 time in total.
use the PM function to contact members and transmit personal info


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