[Project] Fault Detection: Power Quality

Fault Detection: Power Quality is an algorithm that identifies voltage dips and spikes in your home. In a split-phase 120/240V electric panel, each leg should sustain a voltage of around 120V. This experiment identifies fluctuations outside of a normal range.

If you’ve received a notification in the Sense app about a Power Quality issue, we’d like you to share details here in the Sense Labs community. Here is an example of a correctly formatted post.
Please post Power Quality-specific project feedback below.

How to create a Power Quality post for community feedback

  • Title - For the title of your new post, please label the post: Power Quality - [SUBJECT]
  • Completeness - In order for the Sense community to provide feedback or insight, please share the below details when posting a Sense Labs detection to the community. Below is an example of a properly formatted submission.
  • Tagging - Please make sure the entry is tagged correctly as “Power Quality”
  • Consistent formatting - Please make sure you have as many of the above criteria as possible in your post so Sense community members can offer feedback or questions.

Required information to include:

How your Power issue was detected?
Did you notice anything to indicate a voltage dip or spike in your house (flickering lights, etc.)?

Voltage graph screenshot

Event Timestamp screenshot

Resources for Power Quality

Below are some initial resources for Power Quality issues. If you have suggestions for additional resources to add to this list, please reach out to @JustinAtSense.

Types of Power Quality Issues

Brief voltage dips and spikes can be harmless. You may notice voltage spikes and dips throughout the day in your home. If you are seeing a high amount of spikes and dips, please share your information with our Sense Labs community.

Voltage dips can occur when a motor in a large appliance in your home starts up (like a refrigerator), and greatly reduces the energy available for other devices. If you share the same power mains with your neighbors, you might even experience a voltage dip when a large appliance in your neighbor’s home starts up. Dips can be caused by a line-to-ground fault due to a tree falling on a power line or a lightning strike. They can also be caused by a temporary short circuit or sudden load change in utility power lines. You may notice a light flickering or a computer rebooting when a dip occurs.

Voltage spikes are the opposite of dips, but share many of the same causes such as a lightning strike or a short circuit on a utility power line. They can also occur when a large utility load is turned off resulting in voltage on the power line increasing for a short period of time, or when the utility switches power from one geographic area to another as supply and demand changes. Voltage spikes can be harmful to sensitive electronics in your home. However, using inexpensive surge protection equipment can ensure that your important devices remain safe


I just wanted to suggest, can the app/website do a screenshot for me for the time period where it recorded/detected a spike or dip? I just posted a report for my 2 recorded dips, which were several days ago, but the graph of voltage only shows the most recent 24hours, not relevant to the dips.

going even further, it would be nice to be able to scroll back through time of a voltage graph, much we can with the current wattage meter. This would allow me to see the spike/dip.

And of course, being able to plot the voltage graph on top of the wattage graph would be ideal, so we would have device labels as well to see any correlation between dips/spikes and devices.

Keep up the great work!


Thank you @Edison517. This is something we’ve heard from several users, and the request makes sense. We’re still thinking about the specific enhancement here (and can’t commit to a timeline yet), but I certainly understand the use case of seeing the graph of your actual dips and spikes rather than just the 24h.


Does the Dip or Surge have to be outside the 10% or outside the shaded piece to count?

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Just wanted to add a suggestion to have an alert pop up when a spike or dip has occurred.

I’m probably lucky that I haven’t had many dips, but I’ve had a few new ones and if I hadn’t checked the dashboard I wouldn’t have known.

I know that if someone has a LOT of dips, they might get sick of notifications, so maybe the option to turn them on/off would be nice.


Thanks @Edison517. Alerting is certainly on our radar. We’re still collecting data on these experiments and will be rolling out improvements iteratively, but that’s certainly the type of enhancement we’d like to make.


make the alerting optional, for those of us with poor power quality we dont need hundreds of alerts a week or month


@Edison517 This recent catch with the Power Quality lab –

points to more meaningful and deeper analysis that Sense (@EmoryAtSense2) is likely really looking for. I can see why there might be many reasons to have threshold alerts (I’ve asked for them myself) but like all things Sense the magic happens when the alerting is more sophisticated.

One of the Lab’s side effects is going to be that Sense could get blamed for issues. It is easy to explain what is and isn’t under Sense’s control but some users are going to struggle with where that line is drawn. e.g. I can see why it would be better from Sense’s perspective to create simple threshold alerts than “likely failure of X” alerts but only the later is really meaningful to non-technical users.


It also points out that it is helpful to articulate the threshold that has been crossed.

[mod edit: user address removed]


I’m going to repost a link on Power Quality here that I thought was quite interesting. It turns out that most of the negative effects of poor power quality, things like device malfunctions and early device failures, are typically driven by too little or too much energy, which is a function of both power sags/swells, plus the length of those sags/swells. It might be useful to have Sense alert based on the IT Industry Power Quality Tolerance Curve, which also takes into account duration of the sag/swell event.


Just wanted to add a suggestion to have an alert pop up when a spike or dip has occurred.

I’m probably lucky that I haven’t had many dips, but I’ve had a few new ones and if I hadn’t checked the dashboard I wouldn’t have known.

I know that if someone has a LOT of dips, they might get sick of notifications, so maybe the option to turn them on/off would be nice.


I am so thrilled Sense has added this feature!!! I have been wanting voltage graphs since day one!

Now that it is out of course I want a few tweaks!

Can you make this graph the same fidelity as the power meter graph? I want to be able to full screen it and zoom in, etc…

The first step is letting me zoom in and go back through as much history as you are willing to store.

After that, I want to be able to get alerts about power quality events and to be able to get high resolution snapshots of power quality events (beyond average data values that normally get stored). Many power quality events only last a handful of cycles and so averages may not tell the full story.

Where this should be interesting is to be able to watch online tap changers and voltage regulators operate on the utility side (and also when they do switching operations or take restoration actions after a storm).

I love it! Please make it a first class citizen feature!


I was good until Isaias hit last week(<10 drops) . I haven’t had a drop for 5 days so think it was just storm related.
There were power lines taken down across the street (actually, power lines were down on almost every street in the neighbourhood when we went for a walk after the storm hit). They still need to fix some houses down the block. We may get another spike when they are re-connected.

I would also like the ability to go back further. You can export the data until a spreadsheet, however, a graph like the power meter would be simpler.


@eric2, @jonhawkes,
Sounds like your interests in additional functionality lie in root-causing the dips/sags/swells, plus prevention if the cause is located inside your house. But if the issues are caused by utility transitions or storms, what would you hope to learn from a close zoom into the data ? And @eric2, you mention seeing events that cover a few cycles. Would it be OK seeing in the 1/2 second min resolution of the Power Meter ?

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