site lighting control

[omar_beyaty]

I would appreciate your cooperation. I have to control the exterior security floodlights for a site fence.the site around 4sq.km area with 1km long per side .the control room in the end of the site , 64 floodlight to be installed per side. the control method to be done using PLC(LG)....if possible mention the general idea of PLCs connections and if we have to use master slave connection and the location distances might be PLCs assigned and whether we use coaxial or twisted pair in Remote I/O communication with each other ...

thanks

 

[Lancie1]

It sounds like a nice project. You could use a PLC, but there are many lighting contactors and controllers avaialble to do the job without a PLC. I would only use a PLC if it is already part of the site equipment for some other task.

 

[omar_beyaty]

You are right ,Lancie...it is a part of many tasks that PLC doing in site....but the problem is the remote light locations on the fence need PLC slaves to receive the light operation status to be shown on the HMI as they 256 fixture are hard to be monitored visually and my question is about how shall we get those signals over this long distance ,Ive researched many options among using RG11,RG6 and semirigid coaxials OR ethernet...but I need some experts guid me to the proper thing and if we need many NOs of PLC slaves to cover the distance.

thanks

 

[Lancie1]

You are going to need some information about the lighting circuits. How many fixtures are on each electrical circuit? That depends on the watts and volts of the fixtures. Generally you can assume 8 to 10 fixtures per circuit. If each side has 8 circuits, then you need 8 on/off digitial outputs for each side, or 32 total. You could use a Remote I/O module in the center of each side, with a local light fixture power supply and RIO power supply for each, and a Ethernet cable (one cable can loop to and control ALL RIO modules) from each (or another PLC communications protocol) going back to a main control PLC and control HMI. You may even need transformers at the location of each RIO module to reduce a higher main voltage down to the fixture voltage.

For these long distances, you probably will want to keep the light fixture voltage as high as possible, maybe 480, 380, or 277 volts. This will reduce the current on each circuit (that your Remote I/O modules have to switch on and off).

If verification feedback is required for each circuit (or each fixture), then you also need some current-monitoring sensors that provide "Burning/Not Burning" inputs to Input terminals on your RIO modules. You can probably monitor the current on each fixture supply circuit, and use that to determine if any of the fixtures on that circuit are not ON. The currrent levels should be fixed for each numuber of fixtures that are actually drawing power on each circuit. For example, if you are using 400 watt metal halide lamps (which draw about 460 to 480 watts) at 480 volts, the current for one fixture should be about 1 amp. If there are 8 fixtures on the circuit, then the total for that circuit should be about 8 amps. If it is only 7 amps, then probably 1 fixture is not burning. Your PLC monitoring program would have to take into account the starting time for the fixture, depending on what type of fixture you use, to make sure that you are looking at the running currents and not the start-up currents.

Another montioring method would be to use photoswitches at each fixture, but that would require much more wiring and installation costs. Each fixture would have an input back to your RIO modules, where the current monitors only need 1 input per fixuture circuit (which can be located at the RIO panel so that field wiring is minimized).

 

[omar_beyaty]

Thank you very much Lacie...Alot of infos suit practically for our project....It is a nice idea to distribute the fixtures in zones(say 8/side) and the defected fixture to be searched within the specified zone, it is not necessary to locate the defected fixture in program precisly ..Im fully agrre with you about the restrictions of using the photocells and using the current sensing elements would be much better , but could the RIO modules get the latest fixtures signals without attenuation (should we use more than one RIO to decrease the distance between the fixtures and RIOs?)....finally, should we use the ethernet+ethernet switches in communication with the master PLC, OR use the coaxials(RG11 and RG6) and which is better?if we take in consideration the long distance on site.

Thank you

 

[Lancie1]

(should we use more than one RIO to decrease the distance between the fixtures and RIOs?)....

I would plan to use 1 Remote Input-Output module for each side. It really depends on the length of each side. If each side is one kilometer or less, then you might get by with two Remote Input/Output modules, located at diagonal corners of the fence. However, using 4 (1 for each side located in cener of each side) would decrease the length of the wire runs from your lighting fixtures back to each Remote Input-Output module and reduce the total wiring cost significantly.

Finally, should we use the ethernet+ethernet switches in communication with the master PLC, OR use the coaxials (RG11 and RG6) and which is better (f we take in consideration the long distance on site)?

Again it depends on your distances and on which PLC commumincations protocol you are using. RG11 and RG6 are connector types, not communication types. To fully answer your quetion, look at your comm protocol and the maximum distance specifications. If your comm method can handle the distance from your main PLC location to the farthest Remote module (probably at least 1.5 km based on a 1 km side), then you would not need to go to Ethernet. For example, if you are using the Allen Bradley Contrologix Data Highway Plus communications protocol, the maximum length at 57.7 kbps is 10,000 feet or 3 kilometers.

The more information you can supply, the better answers you will get. For example, you have not answered these important questions:

1. Do you have to control the lights (turn them on/off as well as monitor to see the status)?
2. What type of PLC are you using, and what built-in communications protocol does it have available?
3. What type of light fixtures are being used, and what is the voltage and watt rating of each fixture, and how many fixtures are on each power circuit?

 

[omar_beyaty]

thank you Lancie for helpful info's.....it was nice opportunity talking to you

 

[Lancie1]

Omar,

I am sorry that I did not recognize "LG" as a PLC brand. Now I searched and found that LG is a PLC brand for a Korean company called "LG Industrial Systems". Looking at the various LG models, it appears that the built-in commumications protocol called Cnet is mainly a Modbus RS-422/485 type that is good for up to 500 meters at 76.8 bps using a twisted-pair cable. Even if you use "Repeaters" available so that you can use up to 6 repeaters to extend the maximum range to 750 meters, that still would not be enough.

You had better go to the "Fnet" Ethernet communications method, which is good for up to .75 km or 5.25 km using 6 repeaters and twisted-pair cable, or up to 3 km using optical cable.

 

[The Plc Kid]

Ethernet is likely your best road but with that distance and the noise lighting ballasts can give off fiber media would be your best bet.

Using point IO you can do a redundant ring very easily. I have done something very similar even to the point of putting a small CT on to detect load which will give you a indication of a proble such as a blown bulb, ballast, starter, etc.

Wago has some nice ethernet IP distributed IO also and a direct CT module.

http://www.wago.us/products/19972.htm

 

[omar_beyaty]

Lancie

you are fully right....after you i went to same research and found using the Fnet is sufficient for my project like you said.i will be fully commited to this approach and discard other options...thank u ,I appreciate your interest .

the plc kid
yes , the fiber is certainly is the best choice, but , you know the cost , its not worthy to the controlled elements(lighting)....i would use the fibers for greater projects. But i wanna consult you about the current sensing elements (CTs)....if i have flood light using the ballast what would it be the best types of these CTs?

thank you

 

[The Plc Kid]

Omar,

You had better go to the "Fnet" Ethernet communications method, which is good for up to .75 km or 5.25 km using 6 repeaters and twisted-pair cable, or up to 3 km using optical cable.

Lancie what is Fnet? Did you mean Fast Ethernet? or something else?

 

[bce123]

why not just put the plc in the electrical room and run circuts from there?

 

[The Plc Kid]

why not just put the plc in the electrical room and run circuts from there?

I agree.

 

[iant]

why not just put the plc in the electrical room and run circuts from there?

There may be a huge issue with Voltage drop - if you mean supply the lighting from that same room.
Cbus or similar is designed to run remote lighting systems.
with multiple switching points etc.

A friend of mine (yes I have friends) runs his business using the Siemens LOGO PLC (Smart Relay) to control carpark lighting exactly as you are wanting to do.

 

[bce123]

There may be a huge issue with Voltage drop

the voltage has to get there some how. Most plants only have a single point of service and the voltage is going to drop weather it from a feeder or a branch circuit and can be easily corrected with buck/boost xfmrs. I would use 480 volt and just size the wire to handle the drop