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What is your Power Quality telling you?

Sense Team
December 21, 2020

Andrew had noticed mysterious things happening in his home, with some spanning back years, including lights flickering and solar panels failing to operate when other appliances were turned on. After a while, these mysterious events became part of day-to-day life and Andrew saw them as normal.

Earlier this year, Andrew looked in his Sense app and discovered a new Labs project that analyzed the power quality in his home. He realized that his power quality could be causing the odd behavior. More details on Andrew later, but first, what is power quality and how is it measured by Sense.

With the introduction of Sense Labs earlier this year, Sense users started sharing stories about how Labs projects have increased their awareness of what is happening inside their homes. The Power Quality project has been widely shared across our Community and Facebook.

How does Sense Labs Power Quality work?

The Sense Labs Power Quality project measures the electricity coming into your home from the grid and uses an algorithm to identify fluctuations in voltages outside of a normal range.

Above: Power Quality graph from Sense Labs depicting a home with consistent power quality

The Power Quality project shows live voltage readings from both legs as well as a graph of voltage for the last 24 hours. Power Quality also records dips and spikes in voltage outside of a normal range (10%) with a 24-hour graph view of both phases. Sense users can download a .csv file of dips and spike events from the past 30 days.

At Sense, we’ve noticed that power quality issues vary by region and even within a specific utility’s service area. The reasons for power quality issues can be varied and complex. For instance, homeowners in rural areas might see inconsistencies in the electricity they are receiving from the grid if their utility’s infrastructure is old or needs repair. Neighbors like large factories or commercial buildings with big machines that draw a lot of power can stress rural grids, too.

Many fluctuations in power quality can be explained by weather events or utility maintenance, but frequent dips and spikes may indicate an issue with the power feed from the utility or the wiring inside the home. The Power Quality project alerted Andrew and other Sense users to abnormal situations that turned out to be serious.

Power Quality in California

We spoke to Andrew, a Sense Labs user in California that used Sense Labs to track down an issue that has impacted his home for almost eight months before he learned more about the underlying cause.

“I’ve had long term issues with flickering lights when large appliances (such as the AC) turned on. It has been going on for a few years and I thought it was normal. The major issue I noticed was my solar panels shutting down when I turned on my toaster oven and microwave at the same time. Then Sense turned this feature on and reported that I was getting over 680 voltage dips. I called my power company and they sent someone over about three or four days after. Once they had inspected the line coming into my house, they detected that the ground line from the drop-line was faulty and had a team come out to fix the issue immediately.”

Above: Power Quality graph from Sense Labs depicting a home with a faulty ground line

Since the issue was resolved by Andrew’s power company, he hasn’t seen any unexplainable voltage dips or spikes.

Power Quality in North Carolina

It’s not unusual for utility companies to be unaware of issues that occur between the electrical lines and the home. “Sense was able to have a huge impact very rapidly. I had it installed for about six weeks before this issue came about,” said Curtis K., a Sense user in Raleigh, North Carolina. After enabling Sense Labs in his Sense app, Curtis opened Sense Labs to see 74 dips or spikes within the last 30 days. Since he was due for an HVAC inspection anyway, Curtis had an HVAC technician out to his home for routine maintenance and was able to rule out that the power quality issues were caused by his HVAC system turning on.

Above: Power Quality from Curtis K. showing voltage dips & spikes from last 30 days

Curtis shared that he “couldn’t overlay the impact of a device starting with the voltage fluctuations from Sense Labs, but it was clear that they weren’t related because the dips and spikes were not happening with regularity.” This insight gave Curtis enough reason to call his local utility, Duke Energy.

“I told them what I was seeing with the voltage dips in Sense Labs, and that I was concerned that the waveforms were asymmetrical on one of the phases,” Curtis recounted. “Within about 10 minutes, there were three trucks with technicians from the energy company at my house to inspect my electrical service lines and connections.”

The utility technicians on-site were able to confirm that there wasn’t a failed neutral, but there were other signs pointing to an issue with the electrical lines. Curtis was aware that this particular electrical line had experienced several impacts from large branches during hurricanes and ice storms, and could very well be the cause of the issue.

The utility technicians respliced the neutral at the electrical pole and Curtis’ home and repaired the middle of the electrical line connecting his home to the pole. A partial break in the neutral was responsible for frequent spikes and dips that Curtis was noticing. He was even able to connect the diagnosis from the utility with some of his own observations. “There were days with lots of dips and spikes that seemed to be related to wind. It looked like the partial break in the neutral was moving with the wind, causing it to open and close regularly.”

Since the issue was fixed by his utility, Curtis has been able to export his Sense voltage data into a spreadsheet and add conditional formatting so it flags dates when voltage is outside of the normal range.

Have you used Sense Labs to save money or learn more about your home? Share your story with us on Sense Saves, or in the Labs section of our Community.

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