Power meter connection/implementation question

[storm21]

I have a question regarding an installation power meter. I am having trouble figuring out a way to connect this monitor to our system, I work a large prduction facility as a 4th year electrical engineering intern.

The switchboard that I have to hook this up to has a range of ~25-2500 amps. The meter has a nominal range of ~5-10.6 amps. My first thought was to connect a Currernt transistor, and I believe this would work if the source did not have such a wide range. Because of the linear operation of the current transistor there would be no CT I could use to match up these two items.

My next thought was maybe there is a non linear operating CT?

Or maybe if I had several different CT's for each bracket of amperage for example:
[ul]
[li]one that would deal this the 25-200 amps[/li]
[li]one for the 200-1000 amps range[/li]
[li]one for the 1000-2500 amps range[/li]
[/ul]
and then I could maybe switch between these ct's with a system of relays?

I might be over thinking this, but simply put my source has an amp range too wide to be able to directly connect a standard CT directly to my power meter.

 

[VEBill]

"Currernt transistor"

Do you mean 'current transformer'?

 

[storm21]

ah Yes sorry about that!

 

[VEBill]

Some obvious questions arise.

How many phases? Most high power systems are three-phase.

What voltage? One wouldn't want to be attaching a small (low voltage) CT to a medium voltage system; it could end in death and destruction.

Even if you could use a series of relays, how would the power meter be calibrated with the relays always jumping around?

The only rational approach would be selection of a system designed for this application. Not jury-rigging anything.


Disclaimer: High power systems are not my area. Wait for others to chime in.

 

[DRWeig]

Make and model number of your power meter?

Load profile of plant?

Best to you,

Goober Dave

Haven't see the forum policies? Do so now: Forum Policies

 

[ScottyUK]

Rogowski coil sensors are linear all the way up from zero. Less conventional than a CT but very capable, they need an active circuit with a power supply to produce a useable output whereas a CT is a dumb device, and historically this might have been a disadvantage for a protection application. These days it is hard to find a protection relay which doesn't require an external supply, and the days of induction relays have passed. For metering Rogowski coils don't really have any shortcomings other than their limited market penetration so far.

 

[LionelHutz]

I think this is another important question - What is the use of the power measurement from this meter?

Is this for internal energy consumption usage, ie kWh recording? The power when running at 25A will be so little compared to the power running at 2500A that having an error at the 25A level won't change the overall energy total very much. Say you run a 8 hour shift @ 2500A and then idle @ 25A for the other 16 hours in a day. A 100% error on the 25A reading (ie just assuming it's 0A) would only affect the total kWh for the 24 hour period by 2%.