data acquisition

HI,
how do i let a plc acquire data from a continuosly varying voltage and current source such as the from the contacts of a CCB IN A SUBSATION.
1.do i need a transducer, my guess is yes. If so what kind of transducer do i need for this kind of application.
2.the transducer is likely to bring in analog information
now if my plc has A/D module do i need to write say a ladder program for example for the PLC to recognise that an analog signal is coming in and that it needs to do the conversion to digital

hope u guys got some ideas

any help will be appreciated

tanx

At least no one can say you're not PERSISTANT...

You'll need to provide a LOT more details before you'll get much of a response... Remember, we can only work with what you TELL us. Notice the key word there is TELL...

As for your third (un-numbered) question. You've already answered it.

IOW, what is the definition of "A/D"? Analog to Digital, so you don't need to "convert" it again...

But yes, you'll have to write a ladder program, otherwise the PLC is kinda just "sittin' there looking dumb"...

beerchug

-Eric

transducers for example here:

http://www.comadan.dk/

Why would the voltage vary in a substation?
What is normally used to check current? In many cases
Do you know what a transducer is? If not go HERE for tranducer defined
ANY PLC has to be programmed to match the application its being used in.

I may add more later...it depends.

Hi, let me note some things. You can use ,for example,Multitek voltage and current transducers (240v, 4-20 mA outputs). And of course, you have to make some logic: configuration I/O moduls, logic of value passing through PLC to SCADA/HMI, and may be switch on/off,esd logic, it depends from purpose.
Regards.Evgeny.

Maybe the following product will interest you.

Multilin PQM Power Quality Meter

Substation Info

It has been at least 8 years since our plant has installed a new substation and back then the CB's installed held all kinds of info that could be connected through a serial port to a PC.
If it's an older system you would have to decide on what you want to monitor such as Primary or secondary voltage,current, power factor KWH, etc. and then that's what you will need to buy your instrumentation for.
We have a portable power monitor that we use on some 460 volt systems that will give us all the info we need.
As someone suggested you may want to look into that method.

Good Luck

Musical chair posts

People have been responding but you never return to the same post.

Most circuit cubicles as well as incoming CB cubicles have CT's and PT's for Substation instrumentation, you can make use of them with the Allen-Bradley Power Monitor and RSPower software.

Otherwise you will need to transform down your voltage to match your analog module then scale your module units to give the desired reading. (Typically these high voltage circuits do not vary in voltage by great amounts so you may not need great resolution.)

For current, if you can't series your analog module with an existing instrumentation CT then contact a local company that deals with current transducers.

Provide more details and I may (or may not) be able to be more specific.

Roger

Musical chairs ain't the words for it. Since I posted a reply at his last post suggesting that the discussion be kept in the public domain, he has deserted that post.

Here we go again with another post. I am beginning to think that this guy wants somebody to design and programme the project for him. Perhaps we should paste some hourly rates for him to take someone on and do the job. Really, this is pretty basic stuff.

Kim Gold has a very good suggestion. I am just in the throws of writing software (Modbus RTU) for a job where they are upgrading the high voltage protection. Using 6 GE-Multilin 750s and 4 SR489 generator protection relays. Have used them before and, apart from one bad lot of firmware (buggy), have not had a problem.

Really man, most of this is basic. Use your noggin please.

mddr