Voltage Monitoring Device Question

Hello all,
My name is John, I'm working here in ZImbabwe Africa. I have a complex here that uses a 400KVA Generator. We have a lot of dirty power from the public supply company so we often switch over to GEN. I have a control system here that runs off of Mitsubishi Fx2n PLCs' and Citect SCADA interface.

I need help finding information on getting a voltage sensor/monitor/meter that can connect to my existing Fx2n plcs. I want to monitor the voltage and use it to determine when to switch over to Gen power.

So if anyone can help. Thank you so much.
Again I need a Volt Meter and Input Card - for my Mitsubishi Fx2n PLCs

Thanks
JOhn

Lots of ways to do this, what we do is read a power meter from the PLC using modbus but we use the other information for other things

A simple solution would be to use an adjustable phase failure relay which give digital outputs when one phase falls outside the preset limits, you then switch to GEN from this signal

just one link from google:

http://www.squared.com/us/products/relays_timers.nsf/unid/D19099054747188A85256CB60056D979/$file/phaselossrelays.htm

don't want a relay

Yes, thank you for that info, but I already have a 2phase voltage sensor that I use for my change over signal. I want something more precise and to communicate to my fx2n becuase my Gen is way out in the field and my office and monitors are in the buildings. I would like to monitor the voltage 24/7.

OK, you did say you wanted to "Monitor" the voltage to determine when to switch over, thats what the phase failure relays are for and are doing, so what is measuring the voltage going to give you that you havent already got ?

If you want to monitor exact voltage you need to go down the power meter route, you could take a Powerlogic meter with RS485 Modbus comms direct into Citect, as far as i am aware Mitsi FX dont have a Modbus Master.

You may be able to get a meter with other comms on it and put a module onto the FX

Ok, thank you. Yes, I know what the phase failure relay is already doing. What I want is to be able to read the voltage 24 hours a day 7 days a week. It would be helpful to me, because our voltage varies every day! I want to be able to monitor it every day.

SO i need help finding the equipment that I can use. I know what I want. It's finding it that is hard to do from ZIM. SO i need part no's and details.

OK, You need to answer some more questions first !!

For example, how far away is the Gen from the PLC, how far away is the PLC from the SCADA node, are you going to do the programming work on the PLC\Citect yourself, do you want real time readings or a datalogged reading etc etc,

Nobody will be able to give you a detailed list of parts unless you are very specific about your exact requirements.

Have a look at the Powerlogic meters on this site, we use these every day, they give you more than you need but the basic model can be bought for less than £150 UK

http://www.schneider.co.uk/internet/pws/pws.nsf/luAllByID/E1A0BC8BECCF28BE80257199004C81F8?open

You could connect one of these straight into Citect on Modbus RS485 or use the Modnet TCP driver with an RS485 to Ethenet Gateway and trend the values to give you your records

Voltage Transmitter:

https://www.ohiosemitronics.com/products_voltage.asp

John,

I cannot give part numbers without knowing what voltage your generator produces.

Traditionally, to measure and record voltages, first the voltage was reduced (with a voltage transformer, called a "VT" to distinguish it from a "CT", a current transformer) to some low voltage that can be measured directly. Then the low voltage is fed into a voltage transducer that converts it into a DC signal voltage (0-10 volts DC range). This voltage can be read by almost any PLC analog voltage input card, and many other devices also.