reverse power flow blocking device

[HannesZ]

I have a 63A single phase grid connection and I was informed I need to install a  reverse power flow blocking device if I want to connect my hybrid systems(Sunsynk) to the municipality grid. Googling is not helping me so anyone here know of a device that would work? 

Edited November 2, 2022 by HannesZ

[WannabeSolarSparky]

Also commonly known in Sunsynk circles as the CT Coil

[Scorp007]

1 hour ago, HannesZ said:

I have a 63A single phase grid connection and I was informed I need to install a  reverse power flow blocking device if I want to connect my hybrid systems(Sunsynk) to the municipality grid. Googling is not helping me so anyone here know of a device that would work? 

Instead of Google rather just look in the manual. It seems the content in manual does not always come up. All the space is taken by sponsored ads to try and part with your money

Or just look under the inverter section on forum where the CT to prevent export is connected. It also applies to the Deye inverter.

Edited November 2, 2022 by Scorp007

[HannesZ]

Yes. I know the inverter has it built in. So that should be sufficient? they are stating "reverse power blocking to be installed"  on the application 

 

[WannabeSolarSparky]

20 minutes ago, HannesZ said:

Yes. I know the inverter has it built in. So that should be sufficient? they are stating "reverse power blocking to be installed"  on the application 

 

It gets connected to the inverter and hooked onto your incoming grid 63amps, if your installer did everything correctly then the electrician and or engineer will sign off confirming that the feedback (reverse power blocking device) is present and working correctly.

[WannabeSolarSparky]

53 minutes ago, HannesZ said:

reverse power flow blocking device

Just a fancy bureaucracy way of describing devices like the CT coil which can control or direct to control the flow of power in or out of the grid depending on what you are allowed or not allowed in your area/district/municipality.

[Scorp007]

44 minutes ago, HannesZ said:

Yes. I know the inverter has it built in. So that should be sufficient? they are stating "reverse power blocking to be installed"  on the application 

 

Reverse power blocking is just the fancy term to say to prevent export to grid or like some say feed in/back as very few Munics want you to do.

This CT is external and not the one inside the inverter. The one inside cannot detect export to the grid

Edited November 2, 2022 by Scorp007

[Cef]

Hi @HannesZ.

Recently, my local power company went through the torturous process to allow me to export surplus PV to the Grid. That company, along with the regulations of my local municipality, is very concerned that in the event of a Grid power outage, the inverter will comply with the international standards of anti-islanding capacity: IEC 62109. However, and despite the fact that my power inverter complies with said standard, they suggested some kind of external device in case the anti-islanding system of the power inverter failed .
This was solved by presenting a connection diagram with a very simple device that consists of using only a 220 VAC coil contactor with the appropriate amperage for the installation.
The scheme that I show you is simplified since it does not include breakers or other devices and it is just to give you an idea.
In a normal situation, the coil is energized by A1 and A2, the circuit is closed so that both import and export power can flow freely.
If the mains supply is cut, the coil is de-energized, thus opening the circuit, preventing the return of the exported energy.
I hope it helps you.

Edited November 3, 2022 by Cef

[WannabeSolarSparky]

26 minutes ago, Cef said:

Hi @HannesZ.

Recently, my local power company went through the torturous process to allow me to export surplus PV to the Grid. That company, along with the regulations of my local municipality, is very concerned that in the event of a Grid power outage, the inverter will comply with the international standards of anti-islanding capacity: IEC 62109. However, and despite the fact that my power inverter complies with said standard, they suggested some kind of external device in case the anti-islanding system of the power inverter failed .
This was solved by presenting a connection diagram with a very simple device that consists of using only a 220 VAC coil contactor with the appropriate amperage for the installation.
The scheme that I show you is simplified since it does not include breakers or other devices and it is just to give you an idea.
In a normal situation, the coil is energized by A1 and A2, the circuit is closed so that both import and export power can flow freely.
If the mains supply is cut, the coil is de-energized, thus opening the circuit, preventing the return of the exported energy.
I hope it helps you.

That is a nice simple non-smart solution to help satisfy regulations
And those relays are pretty cheap too in the grand scheme of things.

[P1000]

8 hours ago, Cef said:

Hi @HannesZ.

Recently, my local power company went through the torturous process to allow me to export surplus PV to the Grid. That company, along with the regulations of my local municipality, is very concerned that in the event of a Grid power outage, the inverter will comply with the international standards of anti-islanding capacity: IEC 62109. However, and despite the fact that my power inverter complies with said standard, they suggested some kind of external device in case the anti-islanding system of the power inverter failed .
This was solved by presenting a connection diagram with a very simple device that consists of using only a 220 VAC coil contactor with the appropriate amperage for the installation.
The scheme that I show you is simplified since it does not include breakers or other devices and it is just to give you an idea.
In a normal situation, the coil is energized by A1 and A2, the circuit is closed so that both import and export power can flow freely.
If the mains supply is cut, the coil is de-energized, thus opening the circuit, preventing the return of the exported energy.
I hope it helps you.

Except if the coil is already energized, the contacts closed, and grid fails, you could still be powering the relay coil from the inverter through the contacts. There is a specialized anti-islanding device that is a bit more complicated for this sort of application:

https://www.victronenergy.com/accessories/ziehl-voltage-frequency-sensitive-relay-ufr1001e

Aside from that, inverters that comply to IEC 62109 (or perhaps VDE-AR-N-4105, not sure) and NRS097 should have ample anti-islanding redundancy that you don't need something like this.

[Scorp007]

A very interesting chat. I just wonder why we try to reinvent the wheel. The CT clamp is the approved and recommended blocking device and in use by thousands.

[P1000]

2 minutes ago, Scorp007 said:

A very interesting chat. I just wonder why we try to reinvent the wheel. The CT clamp is the approved and recommended blocking device and in use by thousands.

A CT in itself does nothing to the power flow. It just tells the inverter how much current is flowing - the inverter does the rest. But essentially you need to be able to measure current and voltage to be able to prevent export, so in that sense a CT one of the options you have for that (and also the most convenient).

Anti-islanding is something completely different, but you also need to measure current and voltage to detect it.

[Scorp007]

46 minutes ago, P1000 said:

A CT in itself does nothing to the power flow. It just tells the inverter how much current is flowing - the inverter does the rest. But essentially you need to be able to measure current and voltage to be able to prevent export, so in that sense a CT one of the options you have for that (and also the most convenient).

Anti-islanding is something completely different, but you also need to measure current and voltage to detect it.

But is that not what all Synsynk and Deye are doing to prevent export. I haven't really seen other means being emoyed by users.

The CT as I understand it detects the direction and for this reason with the CT it does not trigger prepaid meters into tripping on tampering.

The same on the Solis that I use.

[P1000]

4 minutes ago, Scorp007 said:

But is that not what all Synsynk and Deye are doing to prevent export. I haven't really seen other means being emoyed by users.

The CT as I understand it detects the direction and for this reason with the CT it does not trigger prepaid meters into tripping on tampering.

The same on the Solis that I use.

Yes, I just thought I should clarify. From your post it could be interpreted as just adding a CT to any inverter will work.

[Cef]

The electricity companies are interested in the lives of the operators and that is why when you request to export energy to the Grid, one of the certifications they request is the IEC 62109-xx (where xx is 1,2 ...) as well as the Test Data Sheet of the manufacturer of your inverter. where this standard is met with the Serial No. of your Power Inverter.
Notwithstanding this, and depending on the regulations of the different countries and municipalities, they will request a registered Electrical or Electronic Engineer and with attributions that are their own to assume civil responsibility, for which he does his own tests in the installation of the which is responsible and signs the electrical diagrams presented to whom it corresponds.
If you use an external anti-islanding system, it is a BACK UP system, it is not the main system that corroborates such a condition.
Being from Back UP using such a simple contactor scheme, it will be easily accepted both by the person responsible for the installation and by its municipality, since the Failure Rate of the Contactors is very low.
In general, they are electro-mechanical devices of enormous reliability. When they burn out, in general, effectively regardless of the state of excitation of the coil, they remain in a permanent CLOSED state.
The contactors fulfill a similar function to the many Relays that you have working in your power inverter (which also can and do fail), the difference is that the latter are electronic/optical and the Contactors are electromechanical devices.
As a Back UP device, the use of a contactor perfectly meets the objective with a guaranteed life greater than 10 years and an MTTF greater than 300 years.
In the worst case and if you find a very picky electrical engineer, place 2 contactors in series. Your calculator will tell you the probability that both will fail simultanely ...

[Star Harvester]

On 2022/11/04 at 8:33 AM, P1000 said:

Yes, I just thought I should clarify. From your post it could be interpreted as just adding a CT to any inverter will work.

Do you know if an external reverse power flow blocking device is required with a Multiplus II, if it has an NRS097-2-1 certificate ?

The way I see it if the South African settings are configured in VE.configure it is compliant in terms of anti-islanding and as long as "grid feed in" is disabled in ESS, reverse power flow is also blocked? Having to add external gadgets to get my system compliant is a headache I hope to avoid, DB real estate is very limited in my install. 

[P1000]

14 hours ago, Star Harvester said:

Do you know if an external reverse power flow blocking device is required with a Multiplus II, if it has an NRS097-2-1 certificate ?

The way I see it if the South African settings are configured in VE.configure it is compliant in terms of anti-islanding and as long as "grid feed in" is disabled in ESS, reverse power flow is also blocked? Having to add external gadgets to get my system compliant is a headache I hope to avoid, DB real estate is very limited in my install. 

No, it's not required. Adding a CT only changes the point at which reverse flow is stopped. Without it, only things connected to the output of the inverter will be powered by the inverter or solar. By adding a CT, you are able to also export power up to where the CT is installed. For example, if your geyser is not on the output of the inverter, by placing the CT before the geyser, will allow the inverter to know how much power it uses. With that knowledge, it can "export" just enough power to power the geyser, without exporting to the grid. (It does require the grid to be present)

[Star Harvester]

Awesome thanks @P1000 and also for the explanation regarding the CT. Makes sense. I have everything on AC out 1 and AC out 2 though so not applicable in my case. Good knowledge to have for other installs though