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TIDM-3PHMTR-TAMP-ESD: Tamper detection on Neutral Voltage (not current)

Part Number: TIDM-3PHMTR-TAMP-ESD
Other Parts Discussed in Thread: MSP430F67791A, MSP430F6779

In reference design, TIDM-3PHMTR-TAMP-ESD, talks about tamper detection by Neutral current. 

Customer is enquiring, if there is capability for tamper detection by measuring Neutral voltage. Is there such a tamper scenario? If yes, can this be implemented on MSP430F67791A?

  • Hello Eddie,

    Thank you for your post. I have not heard about this approach to tamper detection before. The phase voltages reference Neutral, so if the Neutral voltage increased (not sure if that's even possible), the difference between the phase and neutral voltages would be less.

    Can you provide more details about why this would be needed? If further details are private, reach out to me directly.

    Regards,

    James

    MSP Customer Applications
  • Hi James,

    This is a new requirement. Consumer deliberately injects the voltage in one phase to make it unbalanced. Hence tampering with the meter reading. Detecting the neutral voltage helps to identify this type of tampering attack.
  • Hello Eddie,

    Thanks for the additional details. In this design, all the phase voltages are referenced to the neutral voltage. If a consumer would inject voltage into one phase voltage, I would assume that this would increase the energy measured by the emeter for that phase. Since each phase voltage is measured independently, injected noise may cause imbalance with the readings (compared to the other phase values) but not functional imbalance.

    Where would the voltage be injected? Can you share an illustration based on the analog front end circuitry from the schematic?

    Regards,

    James

    MSP Customer Applications
  • Hello Eddie,

    After thinking about this some more, you could reference Neutral to earth ground (resistor divider may be necessary) for detecting the Neutral voltage. By utilizing this measurement and the Phase-to-Neutral voltage (since the Phase voltage most likely won't change), you could detect changes to the Neutral. Assuming that three voltages, three currents, and one Neutral current channels are being measured, this would use all seven SD channels of the MSP430F6779(A). Ideally, a SD channel would be used, but since all SD channels are used, perhaps the ADC10 module could be used to measure the Neutral-to-earth ground voltage.

    Regards,

    James

    MSP Customer Applications