Detection of a signal from 1000V line

Discussion in 'General Electronics Chat' started by fraz.kharal, Oct 27, 2010.

  1. fraz.kharal

    Thread Starter New Member

    Oct 27, 2010
    Hi guys,

    I have a setup in which 1000v 50Hz sinusoidal waveform have information signal of 1kHz riding on the 50Hz sinewave. volatge level of this 1KHz signal is 8volts AC.

    can anybody help me to design a circuit to detect the 1kHz signal from 1kV line?

    If I use a potential divider circuit to take 10 v of 50Hz signal then 1Khz signal level will also drop with same proportion... there should be an isolation circuit, between high voltage and signal detector electronic circuitry.

    What cooments from you will be highly appreciated.

    Kind regards,

  2. jpanhalt


    Jan 18, 2008
    Look up high-pass filter.

    Be aware that 1000VAC is dangerous and this thread may get closed for that reason.

    fraz.kharal likes this.
  3. t_n_k

    AAC Fanatic!

    Mar 6, 2009
    Check out the ISO175

    Totally agree with jpanhalt - you must be a suitably qualified & experienced engineer / technician / electrician to delve into this stuff.

    If this is out of your comfort zone - drop it.
    Last edited: Oct 27, 2010
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  4. bertus


    Apr 5, 2008

    The ISO amplifier can only handle signals upto ±10 Volts.
    The isolation can be 1500 Volts.

    I do not think it is safe to work with such high voltages without qualification.

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  5. t_n_k

    AAC Fanatic!

    Mar 6, 2009
    I was assuming a person with sufficient skill would be able to take advantage of the ISO's isolation level spec whilst acquiring an attenuated form of the total signal - the OP had suggested using a voltage divider on the HV side.

    Perhaps I was assuming too much.
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  6. marshallf3

    Well-Known Member

    Jul 26, 2010
    I'm hopefully assuming this composite signal is from the intereor of a device that's already isolated from the mains; in other words 1 KV 50 Hz isn't a line transmission level in your country.

    I'd go at it by making up some series-tuned filters that resonante at 1 KHz along with the associated HV divider.

    Please remember that common resistors aren't designed to be used at this high of voltage. Dividing by 100 (99 Mohms + 1 Mohm) gives you 10V of the "line" which will have 0.08V or the carrier on it. The 1 KHz filters will block the 50 Hz and you can amplify it from there.
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  7. fraz.kharal

    Thread Starter New Member

    Oct 27, 2010
    I would like to thank you all , for your value able comments.

    At this moment I am in simulation phase of project so no hazard of HV. Later I will go through extensive HV protection trainings.

    If I summarize, you guys provide me the following information:
    1. use of high pass filter
    2.use of series resonance filters

    The scenerio is that HV is going to be transfered from secondary winding of a step up transformer to the 3-phase motor and a 1kHz signal is being inserted at y-point of 3phase motor. This signal need to be detected on a phase line near secondary winding of the transformer. or at the y-point of the secondary of transformer.

    Mean to say I directly need to tap 1KV from the phase line and to detect the signal from this line I need to design a detection circuit.

    Now I need your help to design an isolation circuit which can protect signal detection circuit to 1kv line. and this isolator should have a kind of voltage divider circuit who can reduce the 1kv 50 Hz signal to 10VAC mean 100 times lower, but the amplitude of information signal (8vAC 1kHz) should remained significant.

    Waiting for your valueable suggestions.
  8. t_n_k

    AAC Fanatic!

    Mar 6, 2009
    I think you are expecting a good deal to just have the isolated signal equal to a lower 50Hz voltage but with exactly the same 1kHz signal level.

    My suggestion would be to have an isolated scaled down voltage in which the scale factor is the same for both the 50Hz and 1KHz components. Then one would apply some narrow band filtering to extract only the 1kHz component from the isolated signal. Based on the primary signal isolation scale factor and the post filter gain at 1kHz you would then be able to estimate the original 1kHz signal magnitude fairly accurately.

    I would use something like a wide band voltage transducer such as shown in the attached data sheet.

    This would give you a safe signal comprising the scaled 50Hz + 1kHz signals. You can design for a suitable primary to secondary scale factor.

    A post filtering of the output signal from the transducer might be comprised either of a narrow band pass filter centered at 1kHz or a narrow band reject (notch) filter centered at 50Hz. You'd have to do some careful design and prototyping to get exactly what you want.
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