Troubleshooting Data Discrepancy

Here are some steps you can take if you notice a discrepancy between data reported by an Auditor and data derived from a different device or system.

The Auditors family are Class 1 (factory calibrated based on IEC 62053-21) energy meters with +/- 1% accuracy. With more than 50,000 units deployed all across the globe and selected to provide crucial energy data for audits, assessments, and case studies purposes by a range of customers, the Auditors are proven to be reliable and accurate.

From time to time, we do receive support requests identifying potential discrepancies between energy data reported by Auditors and other devices, such as inverter consumption monitoring (e.g. Fronius or SMA) or retail meters, or from third-party services or software, or bills.

While there is sometimes an expected small variation between billing data and our devices, in nearly all cases, these discrepancies are caused by factors other than the Wattwatchers device.

The Wattwatchers support team is unable to respond to support requests of this nature unless the request can point definitively to a fault with the Auditor, or all avenues of inquiry have been exhausted.

If you have identified a discrepancy, please follow the following steps before contacting support.

Confirm the device ID

Confirm the physical installation

• Have you confirmed that the Auditor has been installed correctly? Phase mismatch and polarity issues are the most common causes of data discrepancies between Auditors and other energy measurement devices.
  • Indications that there might be a phase mismatch or polarity issues:
    • Grid or other Load circuits are recording negative power during non-production hours.
    • Solar Generation circuits are recording negative power during production hours.
      Low power factor (pf <0.7) for:
      • Solar Generation circuits during sunny days
      • Elemental/resistive loads when they are running
      • General loads when pulling more than 2A (use discretion when dealing with inductive loads)

Confirm the granularity and nature of the data is the same

• When comparing energy data from Auditors to data from other monitoring devices, have you,
  • Checked the granularity of the data
    Auditor reports data in 5-minutes resolution whereas most of the retail meters report data in 15-minutes or 30-minutes resolution. Data post-processing is required when comparing data with different granularity
  • Confirmed the units of the data
    Refer to the right data column and unit when comparing the data. For loads that have a good power factor, one may accidentally compare the VA data to the W data or be comparing kW to kWh depending on the period of data returned.

Confirm the configuration of the Auditor

Calculated values in our software rely on the Auditor's channel configuration information to be properly set within the Onboarding tool.

• Configuration of the Auditor
  • CTs rating
    • The Auditor captures the energy from the CTs. Wattwatchers offer a wide range of CTs from 60A to 600A. Confirm that the rating of the CTs connected to the Auditor has been set accordingly.
      
    • Do you use CTs supplied by Wattwatchers?
      Wattwatchers can only guarantee the accuracy of the data when using accessories supplied by Wattwatchers.
    • The assignment of the CTs needs to be set correctly as the data will be allocated to a specific column in the database based on this assignment.

Verify the two system's timezones are reported the same

• Timezone
  • Has the Auditor set to the right timezone?
    Having the Auditor set to an incorrect timezone may affect the periodical summary of the energy data that you see on the MyEnergy app or the online dashboard. Set the timezone accordingly to ensure that you are comparing the same dataset.
    That being said, this should affect the data itself as the data is recorded with a UTC timestamp when using the Wattwatchers API and it is up to the user application to apply the correct timezone offsets.
    Use the Onboarding tool via wattwatchers.app to set the right timezone for the Auditor.

Ensure that both systems are using the same methodology for calculated values

Different meter manufacturers may adopt different methods of processing the energy data. The Wattwatchers' dashboard processes the data in a 5-minutes interval which means that for every 5-minutes interval of Grid Connect data recorded, the positive values will be allocated to the Import column where the negative values will be allocated to the Export column. This is not necessarily the case for every meter or energy management system solution. Other solutions may be logging data in 5-minute intervals, but the data may be processed in 15-minute intervals.

While either method preserves the conservation of energy, a different method may lead to different breakdowns in energy imported and exported.

Please refer to the example below.

Notice that from the sample of dataset above, the 'Net' flow is 17 units of energy imported from the Grid. However, when the data is processed in the 5-minutes intervals, it reveals that there are 18 units of energy exported to the grid and 35 units of energy imported from the grid; where when data that is processed in a 15-minutes interval only captures 17 units of energy imported from the grid and no energy unit exported to the grid.

Internally, we refer to this phenomenon as the 'Net Metering energy accumulation process'.

Also, please refer to the dataset below extracted from one of the sites. The site is a three-phase site with a single-phase solar on the white phase. Ch. 1 measures Solar Generation, where Ch. 4, Ch. 5, and Ch. 6 measure the Net Grid.

The negative values recorded by the channels that measure Net Grid are accumulated to the exportsKwh column and the positive values are accumulated to the importsKwh column. Again, different meter manufacturers may adopt different methods of processing the Net Grid data. For example, there are meter manufacturers that sum the total measurement of Ch. 4, Ch. 5, and Ch. 6 before allocating the data to either import or export column.

Wattwatchers provides import and export data measurements for each long energy period, so review the API documentation at https://docs.wattwatchers.com.au/api/v3/index.html to make sure you are processing the data correctly.

Auditor data via API

If you are collecting the data via API, the most common issues are around the timing of the data.

• Have you set the Auditor to the right timezone?
• Are your script and server set to the right timezone?

Auditor data vs other measurement device data

When using Auditor to confirm or check the measurement of another measurement device (e.g., utility meter), the golden rule is to compare the current recorded between devices.

Assuming that the Auditor and another measurement device are configured correctly, the current measurement should be similar between devices despite potential phase issues that may affect the power values reported by the devices.

Things to confirm when comparing energy data vs other measurement device data:

• Do the data show a similar magnitude of Current (A) for each channel?
  If the current data from different devices is showing a similar trend with different magnitudes, confirm the calibration of the CTs or current sensor on each device.
• Are these measurements of current are in the same phase order?
  If they have similar magnitudes but in a different order, check the Physical troubleshooting Auditors section below as there might be phase issues.

Physically troubleshooting Auditors

Phase mismatch

To confirm that the power supply and the CTs have been allocated correctly on a multiphase application, have a licensed electrician perform a voltage continuity test.

The voltage difference between P1 and any naked part of the conductors monitored by CT1/4 should be very close to 0V. If the voltage readings show >400V, it implies that CT1/4 is not clamped on the right phase. The same can be performed for the pairs of P2 and CT2/5; and P3 and CT3/6.

Current mismatch

The Onboarding Tool and a clamp meter are useful when assessing current measures by the Auditor.

 

To confirm that you are dealing with the right CTs:

• Go to Onboarding
• Unclamp one of the CTs
• The CT which reading turns to ~0A is the one that you are dealing with

 

Interference from nearby loads

Make sure that the CTs are not touching other cables or sandwiched by other cables or else, the readings may not be as accurate as they should be. To prevent this, in a cramped switchboard situation, try to clamp the CTs on a less crowded section of the switchboard, then, secure the CTs to the load's cable that it monitors by cable tying the tails of the CTs to the load's cable.

I've done all of the above, and I'm still noticing an issue...

After following the steps above and data discrepancies remain, please send a support ticket via the link below:

https://service.wattwatchers.com.au/kb-tickets/new

Please include the following information:

• The summary of trend/issue that is being observed
• Provide the data that you are working on
• The data from another device(s) that you are comparing our data with
• If the data comes in different granularity, please provide both RAW and processed data that have the same granularity of Auditors' data
• Photos that the Auditors CTs and the other device are measuring the energy from the same line(s) or circuit(s). (SLD is also helpful.)
• Outline the steps that you have done.