# Evaluation of Features Generated by a High-End Low-Cost Electrical Smart Meter
## 2 Preliminaries
### Dint-Rail Meter and Its Interface  
Our experimental setup basically consists of a three-phase electricity meter designed by Meazon S.A., which is installed in the central electricity panel of a house. This meter is capable of remote monitoring and controlling the energy consumption of a household and/or an industrial building [33]. It is a rail-type device with small size (2 DIN), which can be easily installed and implements monitoring, measurement logging and controlling of:  
* Up to three separate power lines/loads;
* A three-phased load;
* An entire electrical panel (single-phase, dual-phase, three-phase).  
The meter was selected as it offers accurate measurements and a detailed profiling of energy load. It supports a wi-fi connection in order to communicate the data generated 50 times per second. Meazon's technology incorporates all the signal processing on the smart meter required to measure the following variables (features):  
* RMS Voltage \[V_{RSM}=\sqrt{\frac{1}{T_{s}}\times\int_{0}^{T_{s}}V(t)^{2}dt},\] (6)
* RMS Current \[I_{RMS}=\frac{I_{max}}{\sqrt{2}},\] (7) for sinusoidal currents. The meter also computes the RMS values of various fundamental and harmonic components of phase currents, phase voltages, and neutral current as part of the harmonic calculations.
* Active power \[P=V\times I\cos(\varphi),\] (8) where \(\varphi\) is the phase angle between vectors \(V\) and \(I\).
* Reactive power \[Q=V\times I\sin(\varphi),\] (9) where \(\varphi\) is the phase angle between vectors \(V\) and \(I\).
* Apparent power \[S=V\times I\] (10)
* Line frequency. Stable on 50 Hz.
* Power factor \[PF=\cos\varphi\] (11)* Crest factor \[CF=\frac{|\text{Peak Current}|}{\text{RMS Current}}\] (12)
* Angle between \(V\) and \(I\)  
The above equations were taken from the Evaluation Board User Guide [34]. Apart from these variables, it also computes energy-related quantities as well as the RMS of harmonics on the phase and the neutral currents and on the phase voltages, together with active, reactive and apparent powers, and the power factor and harmonic distortion on each harmonic for all phases. Total harmonic distortion (THD) is computed for all phases for current and voltage. Another distinctive characteristic of the particular low-cost smart meter when compared to others is that the interval between successive measurements (the sampling rate) is at 20 ms (50 Hz). In Figure 1, two different devices are measured with 1 s interval, which is usually the smallest in the literature for low-cost smart meters, and 20 ms interval. It is clear that with 1 Hz sampling rate important information related to the transients is lost.  
All data generated by the smart meter are stored and processed in a Cassandra database on Azure. This is achieved by an application developed by Meazon that can run on any computer system although for the project needs, this application is integrated to a small single board computer called Janus. Janus has the necessary functionality to run this application and send data on Azure. The application uploads the measurements in the cloud and allows users to analyze the data in a dashboard. In Figure 2, the data flow from the smart meter to the user's screen is depicted.  
Figure 1: Comparing time intervals. (**a**) Measuring fridge’s consumption; (**b**) Measuring TV’s consumption.  
Figure 2: Data flow from the smart meter to the user’s screen.