Make the Most of Portable Meter Test

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portable meter- and installation tester RS350
portable meter- and installation tester RS350



In order to protect the utility revenue it's essential to do regular on-site tests on meter installations. If you are suffering huge losses you should focus on transformer operated meters first.

Those meter installations can be faulty at different points:

  • the instrument transformer ratio does not match with the meter
    typical mistake is a wrong programmed meter
    the fault can be figured out by checking the meter accuracy on the primary side
  • the burden of the instrument transformer does not match with the installation
    typical mistakes are:
    - wiring is too long or wrong cross section
    - a backup meter is installed and overburdens the installation
    the fault can be figured out by doing a burden measurement
  • the instrument transformers have a ratio- or phase displacement error
    the fault can be figured out by doing a instrument transformer test
  • The meter accuracy is out of range
    Old electromechanical meters (ferraris meters) have worn-out uper and lower bearings. If you hear a scratching sound coming from the rotating disc it's likely possible that the meter is running too slow.
  • wrong installation (tamper or mistake of the installer)
    This is the part I saw most often. Let's take a closer look on this.

Wrong Installation

The screenshots below are taken from our wiring simulator. This simulator is part of the portable test equipment RS350. It can also be used on-line from here.

In our example we have a three-phase four wire CT-operated meter 2500/5 A, like it's installed in shopping malls and for small industry. We assume that the consumption is equal to the nominal load.

primary values
primary values
expected vector diagram

The wiring looks like this:

accurate wiring
accurate wiring

What happens when by mistake an instrument transformer for one phase is reversed?

wiring fault
vector diagram
vector diagram
impact on billing
impact on billing

We see that this simple mistake is causing a loss of 66%. Or in terms of money 165,600US$ per month. (20ct/kWh)
In Germany the utilities are inspecting CT installations every 6 months. CT/PT installations are inspected every 3 months.

Conclusion

The real loss reduction does mainly comes mainly from good maintenance of the transformer operated metering installations.

What is your experience with on-site test of energy meters? Leave us a comment below or use our contact form. Thank you for reading.

4 thoughts on “Make the Most of Portable Meter Test

  1. Hello, nice post here. How does one reconfigure a meter? I want it to bear a different meter number

    1. Thanks for the comment. Meter numbers are assigned to the meter for lifetime and can’t be changed.

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