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Isolation of ADE9000 IC with current transformer for Safety concern

Category: Hardware
Product Number: ADE9000
Software Version: 1.0

Hi,

We designed a smart energy meter to measure 3-phase metering . Here we are using the split core C.T's with the output of 0.333V. Our firmware development is completed and is in testing now.

We are in the compliance stage now, the lab is not accepting the split core C.T's because the magnetic core is exposed and there will be chances of electric shock (when touched) to the user while installing and if these is any short happens in the circuit.

Is this the real case?

The lab is suggesting to use closed or round core C.T or need to provide an isolation in the design between the C.T and the ADE9000 IC connection.

Please suggest how to proceed and how to overcome this issue.

Parents
  • A few points that aren't clear to me:

    1. How is the core of the CT going to short to the hazardous line voltage? Are the CT's being put onto bare copper bars/wire?
    2. Typically an in-line sensor is used like a fixed core CT will require disconnecting the load in order to install, which means that the wires after the meter will be safe since they are not connected to the live grid wires. Can that not be done here too even though this is a non-intrusive sensor?
    3. I will say that most commonly we do see fixed or closed core CT's that are built into the meter meaning that the meter has to be intrusively installed. Although I have seen plenty of applications where a split core CT is used to be able to connect up to an existing wire without interruption.
    4. I am not sure what your specific requirements are for your application but I wonder if there is something unique
Reply
  • A few points that aren't clear to me:

    1. How is the core of the CT going to short to the hazardous line voltage? Are the CT's being put onto bare copper bars/wire?
    2. Typically an in-line sensor is used like a fixed core CT will require disconnecting the load in order to install, which means that the wires after the meter will be safe since they are not connected to the live grid wires. Can that not be done here too even though this is a non-intrusive sensor?
    3. I will say that most commonly we do see fixed or closed core CT's that are built into the meter meaning that the meter has to be intrusively installed. Although I have seen plenty of applications where a split core CT is used to be able to connect up to an existing wire without interruption.
    4. I am not sure what your specific requirements are for your application but I wonder if there is something unique
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  •   

    Thanks for your response.

    Here we are using split core C.T's for easy installation to the user. If we use fixed or closed C.T it again costs of installation to the user.

    For better understanding on our design, please find the below installation diagram and the circuit block diagram.

    Note: Here the neutral is directly connected to the ADE9000 IC and also using the neutral as ground reference to the C.T input (capacitor ground).

    Please find the below C.T image for your reference.

    Here the labs concern is, in the design there is no specific isolation between the high voltage (AC) and the C.T. The C.T's magnetic core is exposed and there might be chances of voltage induced into the magnetic core. That might cause electric shock to the installer/user.

    These concerns are related to the test standards EN 62368 and EN 61010.

    Hope this clarifies all your questions. Please help with the solution to move further.