Good day to all.
On a very snowy cold day, an 'arc' warning came on and the inverter stopped its normal work. First time it happens to my 9 month old system. Turning all off for 24 hours did not cure it; had to restart and manually clear the fault.
I am curious... What inverter are you using? What does the manual say about clearing an arc fault? Does it say it will automatically reset or does it require a reset to clear the fault?
When arcing is detected and protection engages; is there a permanent fault somewhere in the underglass, wiring, connectors that will always re-trigger the fault because there is a real weak/faulty DC path?
Arc faults are tricky. Almost by definition, there is a connection someplace that is not solid, but not very good either. Consequently, it is easy for an arc fault to be intermittent. You mention it is a "snowy cold day". I can imagine a couple of scenarios where that could trigger an arc fault, both resulting from a connection that is not very solid.
* As metal gets colder, it tends to shrink. If the contacts in a connection are just barely touching, they could start to pull apart and go from connected to just barely unconnected.... which is the most common case for generating an arc fault.
* As snow or ice builds up on a wire, it could start pulling on a bad connection and make it pull apart. Again, it goes from connected to barely unconnected and creates the arc.
Notice that if things warm up or the snow blows off the cable, the connection could be re-established and the arc goes away. This intermittent nature would be a good reason NOT to automatically clear the fault till the system has been checked over and manually restarted.
The arc fault can happen anywhere along the DC power route. Most commonly it will be at a physical connection but it could be inside the panel or even internal to a frayed wire.
In other words, if a path fault exists, it will re-trigger the arc fault when system is restarted, right ?
After the reset, if there is still an arc, it should immediately fault. However, if there is no arc, the system will work after the restart, but that does not mean there is no problem. As discussed above, arc faults can be very intermittent.
If arcing happened, is there always a visual clue remaining somewhere in the current path ?
What to look for repairing the problem (eroded connectors, overheated parts, blackened conductors, ...?)
An arc will usually create a visual clue at the faulty connection.... but it may be deep in a connector and not visibly obvious without taking the connector apart. Even then, the visual clue may be a very small pin-prick mark where the arc formed.
On the other extreme, the visual clue may be the chard remains after a fire burnt down the whole system.
Can the arc protection tripping be false ..?
Sadly, yes.... and that makes the situation even more vexing. I don't remember the brand inverter, but a few months back there was a thread about a situation where there were multiple inverters with one getting an arc fault. When they swapped the inverter, the problem followed the inverter. Other people reported similar issues with the same inverter. Some people ended up finding a way to disable the fault.
Detecting an arc fault is very tricky. The system has to look for specific patterns in the voltage/current that indicate a 'bad' fault but not trigger on an acceptable arc like the tiny arc you might get when a switch is thrown. If they make it too sensitive, they will get false triggers, if they don't make it sensitive enough they will miss bad problems.
I get the impression that arc fault detection on solar is still evolving and not all companies have it dialed in yet.
Can the arc fault state be triggered by higher household KW consumption, spike or is it always on the DC side ?
I guess anything is possible, but it seems highly unlikely the AC side could cause an arc fault on the DC side.
Have you ever repaired such arc fault cause ?
Yes and no. I have never repaired an arc fault on a solar panel system but did encounter an arc fault with AC once. A friend had just replaced a socket with a combo Arc-Fault & And GFCI plug and an electric blanket kept tripping it. After trying it on a few different sockets we found it only tripped on a plug with arc-fault protection. (GFCI-only did not pop) The blanket went into the trash. (I later wished I had taken it apart to find the fault because it occurred to me that a poorly designed thermostat could cause the problem and it would have been interesting to know if that was the problem)
