Sencing the direction of a/c energy folw.

[Mike_Houston]

Sensing the direction of a/c energy folw.

I have seen this question ask several times in slightly different ways, but have not seen a direct answer. So, let me ask it in a more clear way:

My question is: How can I determine which way the power is flowing in a 60 hz 110vac circuit. Say you have 2 boxes "A" on the left and "B" on the right. One is a generator the other is a load, they are connected together with a pair a wires. How can I determine which is the genreator and which is the load if I only have access to the wires? I know smartMeters can do that in order to Debit / Credit a customer for energy Used / Generated at the locatiion. Can you explain what they sence / measure to determine it?
Thanks
mmoore739@yahoo.com

 

[lurchman]

The simple answer is an H bridge sensor.

But first take a simplistic view with a couple of resistors in the transmission line between the generator and the load,

a---[Rtop]---c

b--[Rbot]---d

If the generator is connected on AB and the load on CD it can quickly be seen that the voltage across AB will be marginaly greater than CD so you know what direction the power is going but importantly you can measure a few things like load current / power as well.

Obviously if you put the load on AB and the generator on CD the situation would be reversed and you would know which direction power is flowing.

You dont actually need resistors to do this you can replace the resistors with coils on a transformer frame and add the other parts of the bridge to get out phase angle etc for measuring power factor as well if you are so declined measure power lost by the load to earth that causes an imbalance that can be used to trip the supply.

 

[Mike_Houston]

The simple answer is an H bridge sensor.

But first take a simplistic view with a couple of resistors in the transmission line between the generator and the load,

a---[Rtop]---c

b--[Rbot]---d

If the generator is connected on AB and the load on CD it can quickly be seen that the voltage across AB will be marginaly greater than CD so you know what direction the power is going but importantly you can measure a few things like load current / power as well.

Obviously if you put the load on AB and the generator on CD the situation would be reversed and you would know which direction power is flowing.

You dont actually need resistors to do this you can replace the resistors with coils on a transformer frame and add the other parts of the bridge to get out phase angle etc for measuring power factor as well if you are so declined measure power lost by the load to earth that causes an imbalance that can be used to trip the supply.

Thanks, you did make that simple. In the new "Smart Meters" that are being installed now, they can sense when power reverses direcction ie if the home is selling power back to the provider. Do you think this is how they decide when that is happening? I would think the tiny voltage drop would be difficult to measure.
mike_Houston