PQ Monitoring

October 17, 2003

In an earlier post I mentioned working with a monitor.  I thought that maybe some of you would be interested in hearing about what I am talking about, so today I will explain (with photos!) 

The particular monitor we normally use in my department is a Reliable Power Meters Power Quality Monitor.  This monitor is very easy to use due to a feature the manufacturer calls "Full Disclosure."  This eliminates the need to set thresholds in the monitor.

Now, lets get to the pictures:

  • This first one is the monitor itself.  The monitor is essentially a computer.  The top row has connectors for voltage input, current input, monitor power, and ethernet connection to a computer.

  • The second picture is of flexible current transformers (or Flex CTs.)  The current transformer is an amazing device.  It allows you to monitor the AC current traveling through a wire without connecting in series with the wire.  The CT loops around the wire and measures the magnetic field, which is directly related to the amount of current traveling through the wire.  These particular CTs are even more impressive because they are flexible (a standard CT is made out of solid iron.)

  • The third picture shows a monitor installed in an air conditioner unit with a laptop connected.  This is from an investigation I was doing last month.  You may notice that the disconnect is in the "on" position.  Most of the work I do is on live equipment.  This is a 480V 3-phase ac unit.

  • Here is a closeup of that monitor in the ac unit. It is pretty cramped in there.

  • This picture shows the CTs installed. There are three flex CTs and one hard CT around the ground (green wire.)

  • Finally, This is a close up of the voltage clips.  These are the inputs into the monitor for sensing voltage.

So, there you have it.  If you have any questions, e-mail me and I would love to answer them.