“Since we don’t we narrow the voltage cut offs higher and lower. Helps a lot with the overloads. We see the overload warning much more often under 200v here. So set the inverter does reject it earlier.”
Thanks for that, sounds like the type of advice I was looking for from someone that has actual experience with the issue.
On a side note, the “Overload Warning” event last week was at the same time that the electricity supplier’s transformer failed (The transformer supplies this property as well as a neighboring property). The transformer was just replaced. So far the input voltage seems more stable than before. But still to early to tell.
Yes. We call it the brownout to blackout. Very often a condition here.
Sometimes it is brownout then bounces back like they were switching our connection somewhere.
Often the 60 second log interval does not catch the actual event.on the vrm It was when i had a logging system on it i saw it.
It is a definite cause of some overloads we see when the inverter is trying to match the incoming and its fading.
Latest “Overload Event” I noticed a voltage drop to ±220VAC and a spike to 55Hz. According to the grid code settings the inverter should diconnect from grid at 42Hz (but with a trip delay of 4s)
Looking at the battery power dip at the same time as the “Overload Warning” I would assume that the inverter did reject or tried to compensate for the grid at this point and tried to drive some of the load from the batteries / PV.
Yup, I would’ve expected n frequency drop in combination with a voltage drop. Seems more and more like the long supply cable. Maybe it’s an effect of compensating for the loads upstream aswell between the ET112 and the MP-II.
@Anarchy2007
Did you consider disconnecting your houses from the grid completely and charge batteries in parallel from the grid?
Grid → charger → battery → MP2 → houses
So you get a DC recharged off grid island.
A used PSU like the Eltek Faltpack 2 HE might do the job. Put it on some 52-54V or control via relay or CAN-bus. There are projects at GitHub for Home Assistant integration. It’s based on EspHome which you might be able to integrate into Venus OS via Node Red.
The grid should not be able to be frequency shifted.
There is a possibility that something is messing with the meter readings.
But i also think it is a problem with grid feed impedence (I²R) (long wires or poor tansformer or both.)
Then the volt var response of the inverter; and then related to feeding back to loads before but not being able to compensate for the volt drop.
Many variables with internet diagnosis being what it is - a shot in the dark.
Possibly the only other thing to look at is ac able dimensions in the system? Since loads are being fed on ac in try sizing up. Unfortunately there is no control over the grid side but everything in the consumer end is.
“There is a possibility that something is messing with the meter readings.”
The Et-112 was replaced about a month or so ago just as a test.
“But i also think it is a problem with grid feed impedence (I²R) (long wires or poor tansformer or both.)”
I went to check out the new transformer today, it’s definitely a new unit. So think I can rule that out. The grid feed cable is around 200M long 4x25mm2 doubled up ie 2x50mm2 (Aluminium, so even higher impedance than copper, but here copper cables are stolen on a daily basis). I knew from the start this might be the issue as Victron described in an article related to “Overload warnings” and high impedance supply cables. But apparently this had been addressed in later FW updates.
I have a few sites with long supply cables (80M - 100M). I have never had this issue before.
On the other hand this is the only site I have with a 200M supply cable and an ET-112 meter also factoring in that everything in this site had been replaced and reconfigured except the ET-112 configuration and supply cable. Maybe time I face the fact that the culprit should be obvious.
The idea is to ultimately move the “AC LOADS” (Heavy loads from grid between ET112 and MP-II) to AC-OUT-2. That was one of the reasons for replacing the 8KVA MP-II with 2x 5KVA MP-II. This will eventually be a double up of the existing system as there are stables and borehole pumps and other heavy equipment that runs on that line.
That is an option, but there are heavly loads like pumps and staff rooms that need to be supplied which in the current configuration can be supplemented with PV power without using battery power or the need to increase the inverter size to run all these loads.
My opinion / theory at this point based on the following:
I) 08:53:22 DC Load surge -2KW
08:53:23 DC Load shifts high 2KW
II) 08:53:22 AC Frequency starts rising
08:53:24 AC frequency peaks at 55Hz
III) 08:53:24 AC Voltage drops from 240VAC to 230VAC
MP-II DC power generation spikes by 4KW (Higher than needed generation)
which causes:
Frequency shifts high (effect of much higher supply than demand)
which causes:
MP-II rejects grid hence AC voltage drops from 240VAC to 230VAC (Grid = 240VAC / MP-II = 230VAC)
I believe the MP-II makes a calculation error at some point (hence the out of wack calculation on Cerbo every time there is an Overload Warning). I believe this behaviour to be caused by the high impedance supply cable.
Any one better educated than me, please give your opinions or corrections?
It seems like the installation connected to grid rather than diconnect as per the grid code settings in Ve Configure (why, unless the installation caused the instabillity)? Extremely odd behaviour?
I just scrolled through the entire thread again to double check the 50Hz grid as I’ve never seen (grid) frequencies go so far out of whack.
What country / grid are you on ?
South Africa, we have power issues, but I’m very sure this is not the grid causing this. I have 2 other installations in the same goecraphical location feeding from the same power line with none of these issues.
Sunday morning, no overload. crazy noises from inverter, frequency shifts and back to normal. As can be seen in the graph the grid is usually very stable at +/- 0.2MHz shift max.
And again, the graphs just below FREQUENCY , Power in ET112 and Power in MP II (this is no miss read or calculation issue as these are 2 different calculations from 2 different sources) show that at the time of the frequency anomaly the inverter switches back to grid. It is supposed to disconnect from grid due to the high frequency (if it is the grid causing the issue???). Would love to hear from Victron, but unfortunately that avenue of support is non existant.
