Introduction

At Verdigris, we understand that timely, accurate and accessible energy data is paramount to making operating and business decisions. In this study, we validate the data accuracy of a Verdigris system compared to an ANSI C12.20 certified revenue-grade meter.

Background

Sub-metering is a common use case for Verdigris systems where the building electrical load is parsed into different meters to differentiate tenancy, end-use, or equipment. When billing for energy and demand, some organizations may require certified revenue-grade meters that meet ANSI or IEC standards for data accuracy. But there are many instances where certification is not necessary for billing revenue, for example benchmarking building zones or monitoring manufacturing lines. In these and other use cases, high accuracy remains the primary requirement.

Approach

We installed a Verdigris system on the incoming mains of a 480/277V wye electrical panel at a distribution warehouse. Verdigris offers different types of sensors based on the rated breaker amperage: split core and Rogowski coils. To compare the accuracy of each type, we installed both sensors on all three phases of the incoming main. 

On the same panel we also installed a third party meter that is ANSI C12.20 certified. The ANSI standard sets the physical, performance and accuracy class for electricity meters. Figure 1 is a diagram of the set-up. 

Measurements from both meters were recorded at 15 minute intervals across five days. Over 430 data points were collected.

Figure 1: Diagram of the installation

Results

The measurements between the Verdigris and third party certified meter were within a 1% accuracy range and fractions less. There was an average 0.5% difference between the third party meter for the hinged sensors and -0.17% difference for the coils. The percent difference is graphed in Figure 2. 

 For the entire sample size, the percent standard error was 1% for the hinged sensors and 0.4% for the Rogowski coils. Calculations are summarized in Table 1. 

Figure 2: Percent difference between Verdigris sensors and 3rd party measurements

   Table 1: VDG vs 3rd party meter comparison of measurements

Conclusions

The high level of accuracy from a Verdigris meter is comparable to a revenue-grade meter that is ANSI 12.20 certified.  Verdigris systems would meet use cases where revenue-grade data accuracy is a requirement

Verdigris adds further value by using the electricity data to compute other energy parameters such as power factor, total harmonic distortion, real and apparent power.  Our enhanced features of forecasting, disaggregation, and intelligent alerts are offered through the application of AI algorithms.

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