Can you fit the coil before the smart meter

 

 

3 hours ago, Basio said:

Can you fit the coil before the smart meter

Yes, there should be very little difference between before and after, other than... the smart meter obviously consumes some power and this should not be charged to the consumer and thus the current reading before and after the smart meter will differ slightly, I doubt it would be more than 1 or 2 mA aka 0.001 or 0.002 A.

This is something you should test, however, the meter will definitely see the energy from the Sunsynk blending & might not like that. The CT coil is a limiter of current. Meaning it makes the Grid port bi - directional. @TaliaBhas already mentioned on a different thread & I agree with him: If the meter is a old school spinning wheel meter then no problems. However, if your meter is digital & not bi-directional that meter might give a tamper error. 

Rather carry out the blending of solar/ battery energy ahead of the meter because that way it does not pass through the meter. However, if the CT is before the meter all that energy passes through & most digital meters will see that as a tamper. 

This tegnology is new to all of us the meter needs to be configured for infrastructure that is typically referred to as ‘Advanced Metering Infrastructure’
(AMI). See below pdf for explanation.

SSEG-Metering-Guide-for-Municipalities.pdf

40 minutes ago, Steve87 said:

Rather carry out the blending of solar/ battery energy ahead of the meter because that way it does not pass through the meter. However, if the CT is before the meter all that energy passes through & most digital meters will see that as a tamper. 

The CT only measures current. If the current before and after the meter is not the same, then there is a problem (excluding the current used by the meter itself, which should be less than the CT tolerance anyway).

2 hours ago, P1000 said:

The CT only measures current. If the current before and after the meter is not the same, then there is a problem

Yes i think we all agree to that statement the current flowing before and after the ct would be identical but the current flow could be in any direction if your inverter is set up to export power. If the load that is connected( essential and non essential is satisfied and pv power exceeds the loads connected utility current will be 0A flowing through the ct from utility direction. Now if the utility power is present and pv exceeds the loads connected you now have a condition to start exporting power to the utility and the current would flow from the inverter through the ct to utility. If you don’t have a bi-directional meter and you are not set up for AMI you need to block that current flow at the ct. If you don't have a bi directional meter and your ct is on the input(grid side of the meter) you will have problems. If you are set up to export to the grid and you have grid failure for any reason(ls maintenance) the export from your inverter will be stopped at the ct. Hence the reason for COCT having a list of approved inverters to ensure compliance during grid failures.

 

Edited January 22, 20242 yr by TaliaB

15 minutes ago, TaliaB said:

If you don't have a bi directional meter and your ct is on the input(grid side of the meter) you will have problems. If you are set up to export to the grid and you have grid failure for any reason(ls maintenance) the export from your inverter will be stopped at the ct. Hence the reason for COCT having a list of approved inverters to ensure compliance during grid failures.

The CT cannot stop current flowing in the case of a grid failure, that is done in the inverter with at least 2 relays in series to meet NRS097 requirements. The CT position before or after the meter cannot affect anything, whether the meter is bidirectional or not.

39 minutes ago, P1000 said:

The CT cannot stop current flowing in the case of a grid failure, that is done in the inverter with at least 2 relays in series to meet NRS097 requirements. The CT position before or after the meter cannot affect anything, whether the meter is bidirectional or not.

The ct supplies the information to the inverter via a milivolt signal the more current flow the higher the millivolts and if the current flow is from utility or from inverter hence the reason the pig tails are colour coded for pos or neg. I had plenty problems with digital meters going into tamper mode just due to harmonics from the inverter just imagine what would happen with full current from the inverter flowing through the non bidirectional meter with the ct on the wrong side of the meter it would for sure go into tamper.

Edited January 22, 20242 yr by TaliaB

32 minutes ago, TaliaB said:

The ct supplies the information to the inverter via a milivolt signal the more current flow the higher the millivolts and if the current flow is from utility or from inverter hence the reason the pig tails are colour coded for pos or neg. I had plenty problems with digital meters going into tamper mode just due to harmonics from the inverter just imagine what would happen with full current from the inverter flowing through the non bidirectional meter with the ct on the wrong side of the meter it would for sure go into tamper.

I think we need to think through the operation. Yes harmonics would affect the CT on either side. 

The CT would measure the same current on either side of the meter as @P1000 explained.

This very current is telling the inverter to reduce generation in order to prevent export if the inverter is set up not to export. If it continues to export with a smart meter where the bit in the meter is to prevent export it will go in tamper mode no matter which side it is fitted. 

Installers are in a great position to test this. Not easy as one will normally exceed the normal distance between CT and inverter. There might be installations where the smart meter is on the outside of the house walls but have only seen it in very old installations. 

I stand to be corrected as I have not installed these CTs. I just assume based on how CTs are used on various systems. At times even on both sides of a circuit breaker. 

1 hour ago, TaliaB said:

I had plenty problems with digital meters going into tamper mode just due to harmonics from the inverter just imagine what would happen with full current from the inverter flowing through the non bidirectional meter with the ct on the wrong side of the meter it would for sure go into tamper.

The harmonics won't change. The inverter responds very slowly to the input from the CT, which is probably where most of the problems you mention originate. That said, whether it is mounted before or after the meter won't change anything.