Negative readings

Two very different things cause negative readings. If there is solar or another generator behind the meter, negatives are real and expected on low-load days. If there is no generation, a negative phase is almost always a current transformer installed the wrong way round.

First question: is there embedded generation behind this meter?

Yes, there is solar or a generator. Then negative consumption means the site was exporting: generation exceeded demand and the surplus flowed back through the metering point. The classic signature is negatives clustering on Sundays, public holidays and other quiet days, and in the middle of sunny days. This is correct behaviour, not a fault.

No generation at all. Then something is wired or configured backwards. A single phase reading negative while the other two look normal is the signature of reversed current transformer polarity on that phase. It quietly distorts your recorded consumption and every bill verification built on it.

What you will see

• Negative kilowatt hours on quiet days.
• One phase reading negative for an extended period.
• A sudden change in the bill with no change in operations, and a negative phase in the data when someone finally looks.
• Large negative water readings, which is a different cause again. See Negative or implausible water readings.

What to do

1. Confirm whether there is any embedded generation behind the meter, including generators, and say so when you report it. This one answer halves the investigation.
2. Look at the phases individually on Technical Analysis rather than at the total.
3. Note when the negatives started. They very often begin at a power event: an outage, a substation trip, maintenance work.
4. Email support@augos.io with the point path, the phase, and the date the behaviour started.

What Augos will do

Support can flip the polarity setting on a measurement point from the platform side and will tell you the exact timestamp from which the change takes effect. Data recorded before that timestamp keeps the old sign. Where the cause is physical rather than a setting, they will identify the phase and ask for the current transformer to be checked on site.

Good to know

• Polarity is a support-side setting on the point. You do not need a site visit to change the setting, but you may need one to correct the wiring.
• Where reversed polarity has been running for months, ask for bill verifications to be recalculated from the date it started. Otherwise your baseline is wrong.
• A consistent, exact percentage shortfall against a utility bill, always in the same direction, is a strong hint of a current transformer ratio or polarity problem rather than a billing dispute. See Understanding a bill verification variance.

Still stuck

Email support@augos.io with the point path, which phase is negative, the date it started, whether there is any generation on site, and a screenshot of the phase view.