site lighting control

[omar_beyaty]

there are no problems about what concern the power feeding circuit...the lighting fixtures to be supplied with AC power with seperated network and due to large conductors we wont face issues in voltage drops , but the question here related basically with the control signals and how could we achieve the optimum solution to convey these signal from the latest fixture to the PLC head.....and the master PLC will control the OFF/ON state localy from the control room as the all contactors located there...but how can I monitor every fixture status, so I need to send a control signal from the fixture itself back to the master plc to decide about the next step, taking in consideration that the signal usually with low voltage and need to be reshapped/boosted(repeater) in the midway to send it again to plc over the long distance....our discussion here to find the best configuration in PLCs to achieve this goal....as we here discussing the LG plc, a number of guys here like Lncie helped me to find the best protocol used with these type of plc called Fnet(fieldbus network) responsible for sending/recieving the control signals to sommewhat long distance(.75-5.25 km) and it is hopfully solved my project problem...next step is to discuss the repeaters of this kind of plc and the connection topology.....

thank you all

 

[Lancie1]

If I have flood light using the ballast, what would it be the best types of these CTs?

A CT (Current Transformer) is a type of transformer and will measure almost any type of sinusoidal AC current, so the type of load is not as important as the SIZE of the load. You will HAVE to know how much current, and the voltage level, that you need to measure. If you want useful help here, you will have to share that knowledge. Is it 15 Amps, 20 Amps, 25 Amps, 30 Amps, or more? If I were you, I would not measure the current of each lighting fixture ballast, but instead measure the current for each lighting circuit (much cheaper). If you measure each fixture, you will have to run at least two additional wires from each fixture back to some CT cabinet. For four 1-kilometer runs, that would amount to a lot of kilometers of extra wire. You could have 10 to 20 fixtures on each circuit, so installing 1 CT on each circuit at the circuit breaker for that lighting circuit will save many thousands of meters of wire.

It seems that your monitoring circuits need to be merged with the lighting circuit design, so that you can locate your CTs at the same point for the lighting circuit power supplies.

SSAC makes a wide variety of current sensors. The DIN-rail mounted DCSA Series might be appropriate for your project, depending on if your circuit current is more than 50 Amps.
http://www.clrwtr.com/SSAC-Current-Monitors.htm

 

[Lancie1]

...the master PLC will control the OFF/ON state localy from the control room as the all contactors located there...

Then you want to locate your CT sensors in the control room near the contactors. However, for these long runs, if it were me designing this lighting, I would locate a step-down 480-volt secondary transformer, lighting panel, and contactors in the center of each of the 4 sides of the fence, and also locate a Remote PLC module there, with a current sensor for each lighting circuit. Is there project specifications that prevent such a design with local field equipment - maybe security/terrorist reasons?

. . .but how can I monitor every fixture status, so I need to send a control signal from the fixture itself back to the master plc to decide about the next step,

Do not monitor EACH fixture, but you can SIMULATE the effect of monitoring each fixture by measuring the current to a known quantity of fixtures with a known expected current level, then use the PLC to figure out how many of those fixtures are not ON. Then you can set up PLC alarms that show how many fixtures are not on for each lighting circuit, and the location of that circuit.

 

[nightex]

what about using light sensors in areas of interest as feedback signal of lightening status instead of monitoring each lamp current individually???

 

[Lancie1]

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

All I know about it is what I read about "Fnet" in the LG Industries manual. Apparently the LG brand of PLC is already fixed in this project, so I saw no reason to look at anything else. "Fnet" is apparently a type of Ethernet protocol used by the LG brand of PLCs, that can be run over the >1 km distances in this project.

 

[Lancie1]

What about using light sensors in areas of interest as feedback signal of lightening status instead of monitoring each lamp current individually???

Sure, let us figure it up. For four 1 km runs of lights, 256 fixtures x 3 wires for a photoswitch (2 power + 1 on/off signal back to PLC) = 4 x 64 x 3 x 1000 meters = 768,000 meters of extra over-sized (#10 AWG or larger) wire.

Maybe this extra photoswitch wire could be cut in half by locating a Remote I/O module in the center of each side, so now we only need another 384,000 meters of wire!

If we only monitor each circuit (already knowing how many fixtures are on each circuit), then we can cut that 384,000 meters of extra wire by about 99.9% down to about 200 meters (or less) needed at the lighting circuit control contactors for the CT sensors.

Maybe this is a oil-connected compound, so cost may not be a big concern. I am sure that we all would be willing to pay a few more cents/liter to allow that extra light-fixture monitoring.

 

[bce123]

perhaps ct at the main electrical room and a vision system could be used to monitor the lights. light travels a long distance for free!a lot of security cams have motion detection that can be sorted by pixel to see change, just a thought.

 

[Lancie1]

Perhaps ct at the main electrical room and a vision system could be used to monitor the lights. Light travels a long distance for free!

That is a good idea to consider. In an uncluttered clear-air desert environment, a vision system might work well enough to spot any fixture that is not burning. A few cameras mounted along each side of the fence might do the job, and would certainly reduce the amount of wiring (compared to photoswitches). A vision system could be used for mutiple purposes, to spot intruders, changes in the fence, and also burned-out fixtures. With multiple uses, it could be the best choice.

 

[omar_beyaty]

Lancie

I definitely decided to apply your idea here of monitoring every circuit with CTs and NOT every fixture , it would be more practical in cost and ease of installation. and the concept of installing these CTs on the main AC feeding panels inside the control room seems good idea as all network elements(control+power) will be gathered in one place for ease of maintenance.

-For the CT selection, i will depend on your instructions above as soon as the fixtures ordered to the site and study its specifications.

- yes,the area is highly security demanding and the power controls/devices should not be reachable by intruders, but we can put the plc repeaters/RIOs in the mid of each side inside secure panels and even in case they devastated, not like importance when power feeding devices fell in hands of intruders.

-How could I/O receive the signal of CT? I have worked with previous power projects , and we were using a special power monitoring devices to receive the CTs signals and process it....how would it be in case of PLC I/O modules?

thank you so much

 

[shawn_75]

Not sure if the technology is mature enough yet, but I'd look into data over the electrical lines. Electrical utilities use this technology for comms between substations. This would drastically reduce your wiring costs given the distances you are traveling.

 

[iant]

@shawn_75 - I am using E/net over the powerlines an home and getting 100 mips
Obviously using same phase and not through transformers - Might work with this application.

 

[Lancie1]

How could I/O receive the signal of CT? I have worked with previous power projects , and we were using a special power monitoring devices to receive the CTs signals and process it....how would it be in case of PLC I/O modules?

You have several choices. The most flexible system would be to use a CT Sensor that has a 4-20 miliamp analog output, so that 4 to 20 milliamperes is proportional to the current of one lighting circuit. Then you would use a PLC analog input module to read the 4-20 mA signal into the PLC. Then you can use math and comparison instructions in your LG PLC program to determine how many fixtures on that lighting circuit are on or off. For example, if the PLC is commanding Circuit 101 to be on, and the fixture Start-Up timer is done, but the current input level is only "7" (where it should be "8" for 8 fixtures), then your PLC program can assume that 1 fixture on Circuit 101 is not ON.

A cheaper alternate would be to buy a CT sensor that has digital on/off relay outputs. Generally these can be set for Minimum and Maximum alarm levels. Then these outputs can be sent to less-expensive PLC digital On/Off input modules. This type of system could only tell you that (based on current level) a circuit has all fixtures ON or not, but could not determine how many fixtures are not working.

 

[omar_beyaty]

Lancie

you mean I can use the I/O Analogue input to receive the CT signal and reflex the changes by software and get it from 4-20mA output?

 

[Lancie1]

You mean I can use the I/O Analogue input to receive the CT signal. . .

Yes to this part.

. . . and reflex the changes by software and get it from 4-20mA output?

You could send the signal to a 4-20 mA output, but probably there would be no need to do that. Once the signal is inside the PLC, then your logic should examine it, make decisions, and communicate those decisions, alarms, or warnings to the outside world, maybe to an operator control panel.

 

[omar_beyaty]

Thank you Lancie