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Important tip for measuring secondary current with AEMC PEL data logger

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    Jan 2014
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    Important tip for measuring secondary current with AEMC PEL data logger

    After troubleshooting AEMC PEL data loggers for close to an hour today, I thought it would be a good idea to share what I learned with everyone.

    In order to measure secondary currents with the AEMC PEL 103 you must be using the MN193-BK current probe! In the PEL software configuration check the box “An external CT is used” under “MN93A clamp (5A),” located in the measurement tab, then enter your primary circuit CT rating.

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    Tech support at AEMC told me that the “MN93A clamp (5A)” string is a typo error in the software, there is no such model according to him. This is the checkbox that should be used with the MN193 probe. I forgot to mention that the instruction manual has the same wording.

    • Current range is irrelevant in this case, as is the 5A adapter box and BNC adapter.
    • Also verify that the switch on the current probe is set to 5A.

    If properly configured, what you see on the PEL display should match what the cubicle ammeter is reading.

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    A little back story…

    When power monitoring electrical equipment with an operating voltage greater than 600 volts we will typically use the CT and PT secondary as our connection points and then program a multiplier into the software that matches our PT and CT ratios in order to read the correct magnitudes.

    With the AEMC PEL power and energy logger this can be a very frustrating task if you don’t have the correct hardware.

    I was tasked with monitoring several feeder breakers in a 13.2kV switchgear lineup. My company supplied me with the PEL monitors, which I am familiar with but have never used in a high voltage application, along with the stock MA193-10 current probes and MN93 CT’s.

    Once everything was hooked up and configured, the meter was reading anywhere from 0.8-1.0 amps on each phase, meaning that the meter was not accounting for the 60:1 ratio needed for the current.

    After tirelessly trying every possible combination of current probes and configuration options I decided it was finally time to call my guy at the test equipment rental company to see if he had any ideas. We pretty much went through everything again over the phone and then he decided it was time to call the manufacturer.

    We talked to tech support for about 15 minutes before we reached the conclusion that I had been supplied the wrong current probes and the only ones that would work were the MN193 because they have a special resistor that modifies the current probe output for use with secondary circuits.

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    MN193 current probe is shown above. Let this be a lesson if you have never used these meters before, it could save you hours of headache in the future.
    Last edited by SecondGen; October 8, 2015 at 12:24 PM.


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