Power backup of entire society

Emil

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A friend in Bangalore lives in an apartment complex that has power backup for all the flats. While the backup power is on, the residents can use only low power appliances like lights and fans. The moment they switch on a geyser or microwave oven, the power to the flat trips and is restored after a brief while. When it returns, if that appliance is still ON, it trips once more and this happens ad infinatum.
He has no intention of bypassing the restriction but just wants to know at any given time if he is on the city power or backup power.
What exactly is the mechanism that trips the connection for higher loads when the power is supplied by the backup source? How does the tripping mechanism detect if the source is the city supply or the generator? He is not sure if the tripping mechanism is a MCB or ELCB.
 

Chaos

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Normally generator is on one phase, heavy appliances are on another phase. This should not happen if his house is wired correctly.
 

Crazy_Eddy

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What exactly is the mechanism that trips the connection for higher loads when the power is supplied by the backup source?
It's called an ACCL - Automatic Changeover / Current Limiter.
Will automatically switch between mains power and generator power (hence auto changeover), but will also limit current on the generator power (to avoid overloading and damaging the DG) which varies with the model/setting.
Havells-Crabtree-Xpro-Spn-Accl-SDL608228882-1-5ceee.jpg
The above is just an example, its a 1 phase model, while the ones they use in apartments are usually 3 phase ones. It will be in the apartment's EB room where all the EB meters and mains/generator bus-bars are kept. I think it's kept there so you have only one set of wires going up to each apartment instead of 2 for both the mains and generator.

but just wants to know at any given time if he is on the city power or backup power.
This is what I've been trying to figure out as well :D The ACCL itself has all the indicator lights, but since this isn't located in the apartment there's no way for us to know. Ideally ACCL manufacturers could have provided a set of terminals to wire some remote indicator lights in your apartment. As of now I just look out the window and listen for the DG noise to figure out when its on backup power.
Edit: You could also run a pair of wires to a Phase + Neutral for both the mains and the generator from this EB room to your apartment and connect it to an indicator light in your MCB panel. Obviously this is not DIY and should be done safely.
 
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Emil

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@Crazy_Eddy - yes I believe that must be it from the way he described it to me. Thanks a ton. I don't think he can hear the DG from his apartment. Too high up.
His basic problem is that he might have the geyser switched on in the bathroom and if it is daylight, he may have no clue the power has gone. In this situation, the power keeps cycling ON/OFF and he is concerned that it will result in the switch contacts burning out. If it is indeed the ACCL, I wonder if this is a electro-mechanical switch or a solid state device.
An electrician told him he will have to route another set of wires from the meter room to his house and separate the wiring for the low power and high power appliances. The quote was upward of 8K.
He was wondering if there is a cheaper/more elegant solution. This is rather esoteric but if it is possible for him to wire a photodetector(transistor or any other) circuit to his home and mount it in front of the DG LED of the ACCL he could have a visual indicator at home. I have no idea what is the distance.
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Normally generator is on one phase, heavy appliances are on another phase. This should not happen if his house is wired correctly.
The current limiting on DG is a desired feature.
 
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vivek.krishnan

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If its ok with him doing some R&D, can he send a pic of the ACCL - I need to see the LED lights? I think we can whip up a small monitoring setup, which will cost him less than 1-2K, depending on the complexity. He will need to do CAT5/6 wiring till the EB however.
 

kippu

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we have a light mechanism to let us know if its DG or EB , although we can pretty much run anything on the dg also