I’m in Central America and have a Victron system with solar, batteries, and 2 MultiPlus-II units. Several months ago I was running into an issue where VRM would show the grid voltage constantly cycling up and down and AC loads also ramping up and down to thousands of watts. I asked on the old community site, and I was pointed to LOM detection issues likely caused by a high impedance connection to the grid. The installer disabled ESS and set up Virtual Switch Ignore AC which resolved the issue, but now I’m not able to charge batteries from the grid, use scheduled charging, and other ESS features.
How is the grid detection different on the Ziehl box, and can I be confident that won’t have the same LOM issues the ESS was having?
Should this be easy for an installer to set up, or is there some advanced configuration required (I assume this is something they haven’t done before, since it’s a smaller company/country).
Mainly I guess, the Ziehl protection relay cannot do the LOM detection better than any inverter. The LOM detection of the Ziehl is purely based on voltage meassurement while any inverter is able to do impedance meassurement. Therefore inverters may feed in some apparent power. If voltage changes, its a big public grid. If frequency changes its a small island. Ziehl cannot do this as the relay cannot feed in any power.
The reason some grid providers like to have a Ziehl relay is the cable lenght between grid connection point and your inverter. This cable length might have significant voltage drop what can be detected by the Ziehl UFR. In Germany we need to use this above 30kVA, in Italy above 7kVA but its needs is discussed very controverse. Ziehl is a small company around the corner here. I know the developers in person and have UFR and EFR models in use with my multiplus installation.
Although Victron does not really publishes any documentation on what their LOMs are doing exactly, your installer needs to check the setup of correct grid code before using anything else.
Thanks for the info! The grid code is set to “None” (this is a single home system with batteries where no feed in back to the grid is allowed). Here is the original thread I found on the old Victron Community site with more details and a video of what I was seeing:
The installer said they didn’t know what was happening, but the solution was to disable ESS and enable Virtual Switch Ignore AC. Someone in that thread above mentioned a possible high impedance connection to the grid, and that does sound like it would apply (we’re far from the transformer and it’s a developing country where I’ve seen strange things done with grid connections).
I’m just wondering if I can’t avoid a high impedance grid connection if there’s anything I can do to get ESS working again (and it sounded like the Ziehl might be a solution since it uses a different approach that wouldn’t be affected by high impedance).
Obviously, the video shows a 120 Volt 60Hz 2-phase system. I dont know many about the grid rules of US-network operators but one thing is sure: You must not connect to public grid without valid grid code. Not dependend from the size of your ESS grid setpoint.
Normally the voltage tolerance of public grids is up to about 10%. This changes always results in overshoots of the ESS grid setpoint regulator. Depending on your installation size, you should always be about 100 Watt negative to avoid any power purchasing.
In any case, choosing a correct grid code (Victrons installer password required) the multiplus performs same voltage supervision than the Ziehl UFR. If your installation goes frequently offline, its possibly a problem of your grid operator to hurt the specifications against the required grid code.
If you continue working without grid code, you probably supply your neighbours in case of grid failure until your Multiplus shut down for the reason of overload.
Edit: Another thing is suspicious in the video: L1 always shows exactly 0 Watt. Possibly there is something wrong with the neutral line in your installation? As the neutral conductor carries unsymmetric part of the load, missing neutral results in excessive voltage changes.
Thanks again for the details! As I mentioned, I’m not in the US (I’m in a country in Central America), and the authorized Victron installer set the grid code to “None” (I watched them set it up), so I’m not sure what’s going on with that. I never had issues with the installation going offline (even with frequent power outages here), and for what it’s worth, everything does work fine now that it’s in Virtual Switch Ignore AC mode, but that does sound concerning if they’ve configured it wrong.
That is definitely strange with L1, looking at VRM this is what I see for the past 30 days:
Unfortunately the installer hasn’t been very helpful with troubleshooting, but I’ll get an electrician to look into that. What exactly would you ask them (to look into a bad neutral connection on one of the phases but not the other)?
Edit: And I just confirmed (turning on a large load). When the battery is low and the Virtual Switch is just letting the grid passthrough, VRM shows L1 on both Grid and AC Loads as 0W. But as soon as solar charges the battery and Virtual Switch switches the grid off, AC Loads does show correct wattage for both L1 and L2.
What kind of grid counter do you use in your AC-In Lines? See ESS handbook page 1 + 2.
No grid counter (energy meter) coupled with data line to Cerbo? All loads on AC out?
There seems too less info about your installation what needs to check everything to make sure its correct. If AC in is connected to grid, ESS and grid code should be used.
Dont know your country, but its also possible to switch off the grid connection by manual switch if the grid is really lousy. ESS also goes on working without grid.
The neutral line check has nothing to do with your Multiplus. Take a AC current clamp and meassure the current of a strong load (e.g. hair dryer) connected to L1. Expect there are no other loads, currents on L1 and Neutral should be equal. Make same check on L2. Take a second load (hair dryer) same time on L1 und L2. Both L1 and L2 should report same current while neutral current should remain null.
If there is a neutral line problem, voltages on L2 will change if you switch a load on L1. This must not happen.
There’s no energy meter in my system. AC feeds into the Multipluses and then on to all the loads from there. I’ll follow up with the installer to see what’s going on with the grid code. And thanks for the details on the neutral line check, we’ll take a look at that too.
