question

dean-d avatar image

Multiplus 2 5kW ESS Overload faults LOM?

We have 2x sites both with similar setups that the Multiplus 2 has cut out due to overload in the last two days.

Setup: Multi 2, BYD, Fronius or SMA inverters on AC out.

The overloads have both happened around 5-6 pm(high load on the grid). Both systems have had lowish battery SOC (around 10-15%) due to overcast weather the last week.

What's interesting is that on VRM the AC out power doesn't suggest the multi is overloaded. Which leads me to believe it could be because of LOM. I have looked in VE configure and they are already set to Type B.

Could this be something other than LOM or is there a fix for cutting out due to LOM?

Thanks, Dean

Multiplus-II
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@Dean_D

https://www.youtube.com/watch?v=4SXtGIx0x5w This is a webinar on diagnosing overload.

What I have seen though in my experience is as the grid voltage collapses the amp draw is higher and if the battery is charging at the same time the system overloads on amps.

If the battery SOC is low, it generally means that the voltage is lower, then amp draw will be higher. So coupled with poor power factor issues you can get an overload.

I have seen a 1500W motor overload a 10KvA, the values seen being drawn from the battery showed the motor pulling very high amps from the battery coupled with voltage collapse this set an overload warning on the VRM.

4 Answers
offgridsystems avatar image
offgridsystems answered ·

I have a customer site that comes up overload when they run a small power tool, etc. The installation is a Multiplus 2 with ESS. There is only grid input connected, nothing is connected to either of the outputs.

I am baffled why the Multi is overloading, when nothing is connected to the output.

Any idea guys?

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Hi @offgridsystems

I am experiencing the same thing. How did you solve this?

Robert

Did you install latest Firmware on your Multi?

xxxx481 February 9, 2021

• False overloads proved still to be possible. A cause for this has been found and a solution is implemented to prevent this.

Hi Markus,

Both MP-2 5k are on firmware 481. Cebro on 2.63. The firmware upgrade doesn't do the trick nor the improvements that are made. ESS was running for less than an hour only using 200 watt's. I read that more logging has been implemented, maybe somebody can have a look at that log (or please tell me where to find this log ;).

I am more then a kilometer away from the transformer. Lines are overhead and there are many many extensions to all sides. Measured it in google earth, more than 5 k of lines and over 45 houses). Asking EDP to improve the Impedance will be impossible ;).

Robert

Hi

If you have that bad power lines, you might have to set LOM disable and use a third party grid protection device to stop the issue.

Regards

Rob D

NZ

Hi Rob,

Thanks, I was already afraid that this would be the answer. Looked into Zhiel protection relays. I don't want to spend an extra € 600,- on a protection device that does a lot and looks very complicated.

Does anybody know some good alternatives that are less complicated and cheaper?

Robert

Hi

Tele NA003 should be a bit cheaper


Regards

Rob D

NZ

robertg66 avatar image robertg66 Rob Duthie ·

Thanks for you reply, I am looking at a Carlo Gavazzi Type PI-DIN VDE-AR-N-4105.

To me it doesn't feel right, especially because I want to achieve zero feed-in. Some of the devices I look at are for systems that start from 30kw and more. I have a 1 phase system setup and this doesn't make sence to me.

I will also look at the Tele NA003, thanks.

I would make sure LOM is causing the overload issue before buying a expensive ENS.
You could disable lom temporarily and look if the overload condition still occurs.

robertg66 avatar image robertg66 markus ♦♦ ·

I have done that, that's why I think it's the LOM I have a problem with.

dean-d avatar image dean-d robertg66 ·

@robertg66 you mention both Multiplus 2, are there two in parallel? We had an overload issue due to 2 being in parallel. We think it was down to low resistance in the AC cables feeding them. Victron recommends long cables when in parallel to provide some resistance.

We ended up changing out 2x Multiplus for a single Quattro as we couldn't solve the issue.

This is confusing because the problem looks like a LOM issue, where the solution is to decrease the resistance in AC cabling.

I used the 6mm2, neoprene cables (H07RNF). All cables are the same length, about 1,5 meter. Both MP-II are right next to the main fuse box.

When I switch the LOM off for testing purposes all works perfect when running in ESS mode. This gives me the idea it has to do with LOM.

I only have to look outside to see the repairs the electricity company have done on the cables ;). When I switch the pool pump or the heating on (3600 watt) I can see the lights dim. It takes a few milliseconds and than it restores. It's the same fluctuation I see when the Multiplus tries to start in ESS mode. When Bulk charging from the grid I have no problems.

I can give it a try and use 2,5mm2 cable.

tj-botten avatar image
tj-botten answered ·

I am having a similar issue but only when connected to a generator. The Multiplus 2 operates fine on mains but when running on generator it overloads after a few minutes.

I am running a Multiplus 2 4kW with a 250/85 MPPT charge controller and have followed the configuration changes as indicated in the following document.

https://www.victronenergy.com/live/multiplus_faq

The only differences that I have is that I am using the "Other" option for the grid code as the "None" option is not allowed with the ESS Helper.

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dean-d avatar image
dean-d answered ·

Just had this happen again. Its as if the multi stops accepting the grid, then the ESS side overloads as the grid cannot power the loads. Has anyone experienced this and know how to solve it?


1592286201743.png (218.0 KiB)
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dean-d avatar image
dean-d answered ·

Thanks Alexandra,

Here is a screenshot of VRM when it happened, not pulling too much load etc. Leads me to believe it could be a poor grid problem. You can see the moment the AC input drops to 0.

The moment the grid gets kicked off and output voltage drops to 230V



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@Dean_D

230V on the output is where the systems are designed to run. All our offgrid systems run at that voltage. So the drop you are seeing is not an issue.

Your grid voltage is higher than most and the multi synchronizes with the grid when it is connected. This allows other features to work such as feedback if it is allowed. So when the grid drops out or is kicked out then the multi makes its own sign wave and voltage. That is what you are seeing in the graph.

Is your Grid supply dropping out or is the multi kicking it out? The only way to know is to see what tolerances have been programmed in. We have set our home one to reject the grid at 250V as higher voltages are not great for fridges and various other appliances.

The graphs are great at a quick over view but I have found that the .csv data is more useful for really crunching the numbers in the system. So check the file out in ms excel for the period of time you have an overload and see what your system is doing.

https://www.victronenergy.com/live/ess:design-installation-manual See Question 8 This may also be an issue. If it is an impedance issue then a change between LOM type A or B may be the solution.

Thanks @Alexandra

The Multi is kicking the grid off, as the non-essential loads stay live but the essentials shutdown when the multi overloads.

I'll check out the CSV files

I checked LOM setting already and we were on the type B which is more relaxed.

@Dean_D

It may be worth your time to check your installation to your DB, is your ac wiring the correct size?

On another note, we have just experienced an interesting thing.

A tree came down taking out some power lines. They were rejoined by the local engineers. Now the one site we have installed has a similar issue to yours. On inspecting the lines we found several joins in it. The higher impedance from the joins is causing the issue here.

The other cause may be galvanic corrosion on the joints at the power poles for your house installation.

Anyway either of these conditions causes higher impedance.

Thanks, @Alexandra We have checked out cables.

Victron has sent out a new unit to try, as they have looked into it and there's no sign of why it would be doing that.

Sounds like impedance could be an issue for a problem like this.