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Current Transformer for MultiPlus-II


Bobby Kaucic
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Hi all,
so I officially give up on trying to find more detail about this "device"

Can anyone please advise what the "Current Transformer for MultiPlus-II" is actually for?
Everywhere I found peaces of info it says that it is for PowerControl and PowerAssist? - I have Power Assist on in ESS setup and it is working fine without this.

Also, somewhere i read that this will prevent feed in to the network - how true is this?

Please can anyone who has this thing or knows more shed more light on this?

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25 minutes ago, Bobby Kaucic said:

Please can anyone who has this thing or knows more shed more light on this?

The CT is fairly old technology and was mostly used to measure the power generated by a PV inverter on the input or output of the inverter. 

30 minutes ago, Bobby Kaucic said:

I have Power Assist on in ESS setup and it is working fine without this.

In most cases your system will work fine without it. 

32 minutes ago, Bobby Kaucic said:

Also, somewhere i read that this will prevent feed in to the network - how true is this?

If you have loads connected before the inverter and you want to feed them by sending power back through the input of the inverter without sending any power back into the grid, you should rather use a Carlo Gavazzi Energy Meter.  

What feedback are you referring too? 

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41 minutes ago, Bobby Kaucic said:

Can anyone please advise what the "Current Transformer for MultiPlus-II" is actually for?

OK, first things first. The CT is a SCT-013-000, which you can get on most hobby sites. Stock standard, nothing fancy about it.

Now for some background about what is going on. The Multi already has two CTs buit in, one on the input side, and one on the output side. In many cases, this is enough. You don't need anything else.

But there may be times you want to "move" the measuring point of the Multi. When you plug in the external CT, it REPLACES the measurement from the internal CT. The rest of the system (eg the GX device, the ESS control software, etc) doesn't even know about this change, it simply treats this reading as the input measurement of the Multi.

Why would you want to do this? Well, for the same reason you'd mount a Carlo Gavazzi meter, but this is a lot cheaper than the Carlo Gavazzi. If you have other loads on the site that you want the Multi to compensate for (eg a Geyser or a pool pump that is connected to the input side), or if you have a Fronius/ABB/SMA PV-inverter on the input side and you're using ESS, and so on. This external CT than takes the place of the Carlo Gavazzi.

So let me quickly list the pros and cons.

The CT is cheaper, and the ESS power adjustment is faster with the CT... but the CT has a short cable and cannot be installed very far from the Multi, which often makes it more trouble than it is worth. You might as well put the non-essentials on AC-out-2 then.

The Carlo Gavazzi meter can be placed further from the Multi (over 100 meters, as far as RS485 can reach), but is more expensive.

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One of the reasons I was looking at the CT was to prevent the backfeed as backfeed does happen after I'm consuming 2 - 3kw (hair dryer, kettle, etc) and the turn the device causing the consumption off - backfeed happens...
This has tripped by meter 🙄

I am not running the geyser and other heavy loads via AC Out 2 as Victron displays consumption amount as AC Out 1+AC Out 2...with out this split, it doesn't work for my need
Also, I have achieved the same behaviour by simply rewiring things by the DB (when power from COJ goes off - geyser is off while everything else keeps working via Victron).

So, ultimately, this device doesn't have any use for my installation/scenario...
The energy meter would only gave use if I was to wire geyser on AC Out 2 so that I can see what is consuming how much from the Venus...AC loads vs Critical loads...

Then I guess that clarifies it 😀

Thank you so much for the explanation guys...if I missed or made any errors, please do correct me 😬

 

El diagram.jpg

Edited by Bobby Kaucic
wrong pic
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15 minutes ago, Bobby Kaucic said:

One of the reasons I was looking at the CT was to prevent the backfeed

It's not going to do that. It's no better than the built-in CT that is already in the Multi. Sorry 🙂

 

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1 hour ago, plonkster said:

It's not going to do that. It's no better than the built-in CT that is already in the Multi. Sorry 🙂

 

Thanks plonkster 
Did I understand correctly when I was reading that in order to achieve no-backfeed, I would need Ziehl Anti-islanding relay?

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6 minutes ago, Bobby Kaucic said:

Did I understand correctly when I was reading that in order to achieve no-backfeed, I would need Ziehl Anti-islanding relay?

Nope. The inverter already has anti-islanding built in. The Ziehl relay is meant for embedded generators that might not have that, or might not have sufficient built-in stuff to comply with regulations. The Ziehl relay only prevents feeding into a DEAD grid. It does not prevent feeding into a grid that is alive and well... 🙂

Remember that power flow with AC is a bit of a tricky situation. You cannot just look at the direction of the current flow. With AC, the current flow changes polarity 100 times a second. The current flow also isn't necessarily in phase with the voltage (inductive loads, capacitive loads, power factor), in other words for really short times it is possible that the voltage goes one way while the current goes the other way! To work out the power flow you have to work out whether the product of the two are on average going this way or the other way...

Then once you know it is going the wrong way, a relay also can't do anything except to disconnect from the grid completely... which is not really something you want to do.

I really know of only one solution: A power diverter. This is unfortunately not a problem I have, so so far I've not really had the motivation to mess with it.

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Thanks a mill, yet again - you thought me something new :)

Waiting for COJ to come and replace the meter and then we'll see what happens....I saw that Hexing meters can be setup to accept predefined duration (one can setup the any desired time) of feedback so that the contractor doesn't trip...

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18 hours ago, Bobby Kaucic said:

One of the reasons I was looking at the CT was to prevent the backfeed as backfeed does happen after I'm consuming 2 - 3kw (hair dryer, kettle, etc) and the turn the device causing the consumption off - backfeed happens...
This has tripped by meter 🙄

There is no way to stop this from happening. Replacing the meter is the only solution.

We have been trying to stop the meters from tripping for years now, but no-one could come up with an device to stop that from happening yet.. 

 

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