Sunsynk not charging from AC, with erratic AC frequency

[Deondup]

Need advice please, as I experienced an odd error during early hours of this morning. Our power went off (incoming mains remained, no issue) at 2, due to LOW VOLTAGE Error,as the SOC was at 17%. All as it should be. Issue is that AC didn't charge as per my parameters, where it should be kept at 45% by AC. What I found very interesting is the AC frequency being very erratic, starting just before 10pm, last night. I bypassed the inverter, so we can at least have power, and DC is charging very well like always. Could this be a faulty CT coil? How do I reset this, to get back to normal, and undo the bypass, and thus using municipal? 

Graphs is from Solar Assistant.

Edited September 30 by Deondup

[madness_za]

You have a supply problem. The synsynk is sensitive to grid frequency and voltage.

[ccrause]

The grid frequency seems unbelievable, especially the 0 Hz portion when the grid voltage seemed OK.  My suspicion is that there is a frequency measurement problem on the inverter side.

[madness_za]

40 minutes ago, ccrause said:

The grid frequency seems unbelievable, especially the 0 Hz portion when the grid voltage seemed OK.  My suspicion is that there is a frequency measurement problem on the inverter side.

Where are you based? I have seen similar frequency and voltage spikes in my own supply here in Jhb.

[Deondup]

Hi thanks, based in Pretoria East. How does one fix it though? 

[Bobster.]

The problem you have here is eliminating two possibilities. These are
1) Poor grid supply
2) A measurement problem on the inverter.

Buy yourself my favourite gadget, a Kill-a-watt. Plug it into a non-backed up socket. It will display both grid frequency and grid voltage. If the inverter starts complaining and the kill-a-watt agrees then your incoming supply is not great. If the inverter complains but not the kill-a-watt then you need to start looking at your installation.

This does mean that you have to watch the inverter and then check the kill-a-watt in real time. 
 

[Deondup]

Thanks @Bobster. Makes perfect sense. What bugs me though and potentially points to problem no 2, is why now. This installation has been working without any hassles for nearly two years. Saying that, is there perhaps on possibility no 1, a case where the equipment from the municipality have become unstable, at the box on the street?

Interesting thing I also noticed on both Solar Assistant, and the Inverter display, is that the Frequency goes to 0Hz, which explains the graphs, which I posted this morning.

Last question (silly one perhaps). Could it be that the CT coil in the DB board, going to the inverter, becoming faulty? Or does the CT only measure W, and V?

 

Edited Monday at 02:29 by Deondup

[ccrause]

6 hours ago, madness_za said:

Where are you based? I have seen similar frequency and voltage spikes in my own supply here in Jhb.

I'm based near Sasolburg.  I've checked the data over the last two weeks and the largest deviation I could spot was 0.5 Hz away from 50.  Below the grid frequency trend for yesterday.  The daily plot over the last two weeks never looks noticeably worse than this.

 

[Bobster.]

16 hours ago, Deondup said:

Thanks @Bobster. Makes perfect sense. What bugs me though and potentially points to problem no 2, is why now. This installation has been working without any hassles for nearly two years. Saying that, is there perhaps on possibility no 1, a case where the equipment from the municipality have become unstable, at the box on the street?

Something has deteriorated, that's clear. When I got my system installed the grid supply was either fine or we were load shedding. But then a couple of years later the voltage started dropping and the inverter would disconnect and start using the battery (irrespective of SOC). In this case it was the municipal equipment that had been damaged by shedding and cable theft. 

I'm not saying that it has to be grid and can't be any part of your install, but you have to eliminate things one by one to find out where the problem lies, or call in an expert.

16 hours ago, Deondup said:

Interesting thing I also noticed on both Solar Assistant, and the Inverter display, is that the Frequency goes to 0Hz, which explains the graphs, which I posted this morning.

As I understand SA it is driven by your system. So the two will tend to agree with each other. That's why I recommended directly testing the grid on a non-backed up socket. 

16 hours ago, Deondup said:

Last question (silly one perhaps). Could it be that the CT coil in the DB board, going to the inverter, becoming faulty? Or does the CT only measure W, and V?

I don't have the expertise to answer that.

Edited Tuesday at 07:06 by Bobster.

[JustinSchoeman]

It is pretty much impossible for the grid frequency to vary that much.

That would mean either a measurement fault (inverter), or a significant amount of noise/non-linearity on the supply, which is causing bad measurements.  I would guess the latter, but no idea how to test without the proper equipment.

[Scorp007]

21 minutes ago, JustinSchoeman said:

It is pretty much impossible for the grid frequency to vary that much.

That would mean either a measurement fault (inverter), or a significant amount of noise/non-linearity on the supply, which is causing bad measurements.  I would guess the latter, but no idea how to test without the proper equipment.

With a 3000/1 ratio one gets only 30mA on the secondary 2 wires at a 100A. Thus one would need a very sensitive ammeter to measure if it is working as it should. 

This being why as mentioned one needs the right equipment. 

Just a piece of just info. Over the weekend I found my Axpert showing a 45Hz reading for grid and inverter output. I knew this was wrong as ALL utility generators would gave shut down at such a low level. After I switched off my PV and back on both readings went back to normal. 

[Deondup]

Ok problem solved; software issue it seems. First did an upgrade of firmware, but then the system still didn’t charge the battery from AC. My installerer fiddled on software settings and we’re back. So obviously not supply as that is impossible. I’ll repost the software solution when I receive it. Thanks for all the positive input.