Dips and Spike in Solar Output? Not Normal!

[Manny1314]

Hi,
It’s just my first day of using sense. It may be too early to post this but I am really curious what these dips and spikes are for my solar system output? I dont think it’s normal.

Time Sequence. Or Timeline of the event. See screenshot.

3:20:18 - Normal power generation 101W.
3:20:21 - Negative power. (-14W).
3:20:25 - Spike in Power Generation 126W.
3:20:30 - Normal power generation 101W.

There are many such events at different watt levels. I am curious if anyone observe such blips and spikes in thier power production?

I cannot see current (amps) quantity anywhere in the app so I am not sure how to conclude this event. I have requested sense to include amps and power factor in the app since amps is the common quantity we use for defining power consumption. Like, 15Amp breaker, 15Amp circuit, etc. Electricity is all about amps.

[kevin1]

Very interesting ! I’m betting that Sense is measuring accurately and that this is a real phenomenon caused by your inverter(s).
It looks like it is only a few seconds long and based on your snapshots, is only visible at low power generation. A few questions:

1. is this “glitch” only a few seconds long ? How long ?
2. Does it happen at higher production levels, above 1 kW ?
3. What kind of inverter(s) do you have ?

[ben]

Have signal checks completed on your setup? I see there is no consumption at all. Only solar production. I ask only because if Signal check is still going on, results may not be correct yet.

That said, as Kevin pointed out, this does look mechanical. The nearly flat line on your production looks like an inverter that has hit its max output. The blip to me says that it is the inverter resetting or something along those lines.

What kind of solar do you have. What kind of production are you expecting.

As for amps, I guess I would disagree with you a bit. If Sense is primarily about device detection, we refer to devices by their wattage, not amperage. You have a 100w light bulb. Or a 3500w hot water electric heater. And for solar, at least in my area, we talk about solar by its AC or DC wattage size, not its amperage. How would amperage help you in this current situation?

[Manny1314]

Ben. Let attempt that again. FYI, I still haven’t hooked up my main CTs yet to service mains. I have parallel feed so I am waiting for utilitiy to come and help me put them on service main where I have 2 conductors.

Yes, it appears modules switching now when I look the fresh data at higher power. I will wait for sense to start working when I have installation completed. I am just done with solar for now.

I have 5KW, Solar city (now tesla) installed in 2015.
It has ABB PVI-5000 Inverter.

Yes, agreed. Sense is all about sensing what’s going on however I come from a power system background, and we don’t deal with power at all. I was just trying to use amps to figure out problems that I might have in my system. If I see amp I can easily trace and conclude what it could be that inverter doing along with other supporting information. inveter produces harmonics which also can affect how power is calculated. It’s best if amp quantities available for any device which is a straight real power consumption since we have voltage, frequency, etc. Sense CTs are capturing Amps only, and use voltage information to calculate real power. So all I was asking is if CTs can just give me amp value, it’s going to be very useful piece of information.

May be I am wanting sense to give me industrial grade information such as amp, power factor, which may not be feasible for a device which is primarily designed to sense and not monitor electrical quantities.

I was asking because sense CTs already using Amps to calculate power.

[Manny1314]

1. Yes, it’s about 6 seconds. To me it appears that inverter is kicking off and on internal modules based on DC current goes through it.

2. I just checked it happens at higher wattage as well. See new screenshots from today. It’s about 3-4 seconds. Most likely internal modules switching, based in it’s set algorithm? May be if other inverter has similar signature, it can be concluded normal. May be sense has more info on other inverter? Otherwise I should as ABB on this behavior assuming sense does its job accurately.

3. ABB
   PVI-5000 inverter.

FYI. My main CTs are not hooked up yet. I have parallel feed so I am hoping pg&e guy can let me hook up on mains under the meter section. Once that is done, I will reset the data and observe fresh data.

[kevin1]

I have a 4.2kW Solar City / Tesla system from 2013 on PG&E, but have a SolarEdge inverter, not ABB. I don’t see these little artifacts in my solar production.

On current and power factor - You can probably read the Power Meter and the power display, per leg, in the settings, as a proxy for current since the RMS voltage should remain in a narrow band around 120V, except perhaps during large fast current spikes, or unless your are looking at a sub 60Hz cycle measurements. Sense does do detailed measurements of positive-going and negative-going transitions so it can do detections and ships that data back to the mothership. But I don’t think the Sense monitor sends continuous, detailed data back for voltage, current, phase, etc. on each leg (only 1/2 second aggregations). If you want a little insight on data that does make it back, watch the Data Science portion of this webinar - you’ll see that the Sense monitor does report things like phase angle during a transition of interest.

Sense Webinar - August 2018

[Manny1314]

Thanks @kevin1.
Ok. Well, it’s definitely needs to be looked into.
It’s consistently Happening for my system.

Glad to have sense installed. Will find out why it does that. And will update you here. Thanks for all insight.