Load Sheading Project

Discussion in 'General Electronics Chat' started by RodneyB, May 25, 2015.

  1. RodneyB

    Thread Starter Active Member

    Apr 28, 2012
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    Over the last several months I have been building up my alternative energy system as in Zimbabwe we are plagued with power cuts.

    I would like to be able to find out what load each circuit is drawing and then be able to set a power limit for the circuit. When the limit Is being reached it switches off that circuit and then can be reset manually at my discretion.

    Is this possible? My question at this point is what must I be researching to get knowledge and information to build this circuit.
     
  2. MikeML

    AAC Fanatic!

    Oct 2, 2009
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    I assume the AC power has already failed and you are running on an inverter/batteries/solar/generator when you need to make this determination?
     
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  3. RodneyB

    Thread Starter Active Member

    Apr 28, 2012
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    Yes the AC power would have failed and I will be running from a Inverter.
     
  4. MikeML

    AAC Fanatic!

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    This is more a matter of prioritizing the need to keep the loads powered. For example, your fridge can be interrupted for a few minutes without food spoiling, but you have to get it power within an hour or so. OTOH, you computer cannot skip a beat until you save files and then power it down manually...
     
  5. RodneyB

    Thread Starter Active Member

    Apr 28, 2012
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    This s exactly it. I have a substantial battery bank but we are not having enough time between load sheading to re charge the batteries. So What I have been doing is running around switching things off. However If I am not here I have a problem.

    I am adding solar charging which will help and thanks to you I have a low voltage battery cut out. However the system would be better if I could prioritise circuits and then switch off automatically.

    I would also if possible like to be able to set power consumption on individual circuits to avoid abuse.
     
  6. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    Assuming your voltage is constant(-ish), it sounds like each circuit needs current-transformer > comparator > logic-controlled latching cut-out. Then discrete logic or MCU could apply priorities to control the cut-outs.
     
  7. MikeML

    AAC Fanatic!

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    Actually a simple timer/sequencer (Arduino) could do it. All of the load measurements can be done apriori. Remaining state-of-charge in the battery is the independent variable. The dependent variables are which additional loads to dump as the battery runs down...
     
  8. RodneyB

    Thread Starter Active Member

    Apr 28, 2012
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    So If I understand this correctly, I will need one circuit to monitor the battery state of charge, then another which will switch off the loads in order depending on their priority and load
     
  9. tindel

    Active Member

    Sep 16, 2012
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    Rodney yes - you have the right idea. You need an Amp-Hour Integrator (AHI) on your battery. You could put the AHI information into a microcontroller or a raspberry pie (or something of the like) and once the stored energy in the battery starts getting low then you can start turning off loads with the discrete outputs on the controller.

    I agree with what someone else said - you want to start turning things off that are the least important... not based on total load - not typically anyway.
     
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