# A Cyber-Physical Approach for Residential Energy Management: Current State and Future Directions
## 4 Data Acquisition
### Metering Devices  
The basis of residential energy management lies in metering. In the IEC TS 63297:2021 standard (see [[https://webstore.iec.ch/publication/66131](https://webstore.iec.ch/publication/66131)]([https://webstore.iec.ch/publication/66131](https://webstore.iec.ch/publication/66131)) (accessed on 15 March 2021)), [[https://webstore.iec.ch/publication/66131](https://webstore.iec.ch/publication/66131)]([https://webstore.iec.ch/publication/66131](https://webstore.iec.ch/publication/66131)) (accessed on 15 March 2021)), sensing devices have been defined as gateways between the physical electrical installation and the system's data analytical. This standard was originally conceived for NILM. Considering that in every HEMS application, a certain number of points for sensing are needed, all with the same functionality (sampling at an adequate rate), it is possible to generalize the definition given in the IEC TS 63297:2021 standard to a more holistic approach related to HEMS. Therefore, the characteristics of residential energy management sensing devices are defined by three main parameters, shown in the schematic of metering device of HEMS in Figure 6:  
* Input sampling frequency: The frequency at which the electrical signals are sampled by the metering device. This parameter is essential to the electrical waveforms production characterization. * Output rate: The rate at which the metering device produces data that can be used by the Data Analytics stage. Typically varies from 1 set of data-per-second to 1 set of data-per-30 min. Figure 5: Schematic diagram for appliance categorization according to the target application. * Data bit rate: The average bit-per-second (bps) over an hour at which the electrical signals are quantified by the metering device. Typically varies from a few bps to the Mbps range. In a household, there are current and voltage metering devices on the main power supply to measure the electricity consumption in an entire household. Additionally, there may be metering devices for specific appliances, as well as ambient sensors distributed throughout the household. The measurements are either sent directly to a central data server from the sensors or data are processed by the local data processing unit and then sent to the central data server. A central data server can be in the household's domains, i.e., installed in the Home Area Network (HAN), or at the utility level, which receives load data from multiple homes, i.e., the neighborhood area network (NAN) [43]. In a household, the metering devices can be installed at different levels. Therefore, HEMS can be categorized into four different groups according to equipment deployment granularity in the Data Acquisition stage. A general model of the three groups is shown in Figure 7.  
* Grid level: The metering device is set to measure the aggregated power consumption of the household, i.e., the utility's energy meter. * Area level: The metering devices are used to monitor household areas, measuring the consumption after the utility's energy meter. * Plug level: The metering devices are located next to the plugs to monitor directly appliances connected to the outlet or multi-outlet. * Appliance level: The metering devices are embedded directly in the appliances or placed in a dedicated outlet (i.e., outlet for a specific appliance). The smart meters are one of the key systems of future smart cities, forming an AML. These devices collect information on energy use and send it safely to the service center or operations and control center of the smart grid [91]. Taking advantage of smart meter readings, the consumer can know how much energy is consumed in real-time, and decide whether to disconnect from the grid or not (depending on the price of electricity at that time). For utilities, it reduced the need for many labor-intensive business processes, such as manual meter reading, field trips for service connection and disconnection, on-demand reads, power outage and restoration management, and other metering support functions [3].