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The analysis of voltage and current waveforms is important for estimating the quality of the electric power system. In this paper we propose a non-invasive approach for measuring the voltage waveform of conductive elements such as wires or cables. This non-intrusive sensor does not require any electrical contact to the mains electricity, which makes the measurement much safer and easy. The voltage is measured by exploiting coupling-capacitance elements. With this approach, the harmonic content and the amplitude of the voltage signal is evaluated and transmitted. We also present a wireless sensor network designed to implement the proposed non-invasive voltage measurement method. Each node features a low-power, 32-bit microcontroller and a wireless transceiver to send data via the IEEE 802.15.4 standard. Finally, we compare the proposed non-intrusive method with measurements using the direct access to the wire and we demonstrate that we achieve high accuracy with a maximum error lower than 1%.

We present the design of a Wireless Electrical Energy Metering node (WEM) for the integration in a wireless sensor network. The node has energy harvesting capability for long lasting monitoring, and measures the power consumption, of residential and industrial appliances, in the range 10W--10kW. Energy harvesting makes the monitoring activity completely energy autonomous by exploiting a single current transformer to scavenge energy from the electromagnetic field of the main and to perform the measure of current consumption of the load.

Monitoring current and voltage waveforms is essential to evaluate the energy consumption of a system and to improve its efficiency. In this paper we present a smart meter for power consumption which can measure both current and voltage without any physical contact to the electric load or to the conductors of the power cables. This makes the power metering much safer and easier; furthermore an energy harvesting module based on inductive coupling provides power supply to the meter without any need of batteries or plugs to the mains. We describe the innovative contact-less voltage measurement system, which is based on capacitive coupling and uses an algorithm with two pre-processing channels for self-calibration and to provide accurate measurements regardless the cable type. The three-phase version is capable of measuring the three-phase power consumption of an electric load in a complete contact-less manner. In comparison with commercial high-cost instruments, experimental results of our low-cost smart meter demonstrate similar high performance with maximum 3Â % deviation from the reference value.

Transient computing systems do not have energy storage, and operate directly from energy harvesting. These systems are often faced with the inherent challenge of low-current or transient power supply. In this paper, we propose “power-neutral” operation, a new paradigm for such systems, whereby the instantaneous power consumption of the system must match the instantaneous harvested power. Power neutrality is achieved using a control algorithm for dynamic frequency scaling (DFS), modulating system performance gracefully in response to the incoming power. Detailed system model is used to determine design parameters for selecting the system voltage thresholds where the operating frequency will be raised or lowered, or the system will be hibernated. The proposed control algorithm for power-neutral operation is experimentally validated using a microcontroller incorporating voltage threshold-based interrupts for frequency scaling. The microcontroller is powered directly from real energy harvesters; results demonstrate that a power-neutral system sustains operation for 4–88% longer with up to 21% speedup in application execution.

Monitoring current and voltage waveforms is fundamental to assess the power consumption of a system and to improve its energy efficiency. In this paper we present a smart meter for power consumption which does not need any electrical contact with the load or its conductors, and which can measure both current and voltage. Power metering becomes easier and safer and it is also self-sustainable because an energy harvesting module based on inductive coupling powers the entire device from the output of the current sensor. A low cost 32-bit wireless CPU architecture is used for data filtering and processing, while a wireless transceiver sends data via the IEEE 802.15.4 standard. We describe in detail the innovative contact-less voltage measurement system, which is based on capacitive coupling and on an algorithm that exploits two pre-processing channels. The system self-calibrates to perform precise measurements regardless the cable type. Experimental results demonstrate accuracy in comparison with commercial high-cost instruments, showing negligible deviations.

Energy efficiency in smart buildings requires distributed sensing infrastructure to monitor the power consumption of appliances, machines and lighting sources. The analysis of current and voltage waveforms is fundamental for gathering diagnostic information about the power quality and for reducing power wastage. Moreover, it enables Non-intrusive Load Monitoring (NILM), which is the process of disaggregating a household's total electricity consumption into its contributing appliances, by analysing the voltage and current changes. In this paper, an innovative full Energy-neutral (i.e. battery free) and Non-intrusive Wireless Energy Meter (NIWEM) is presented to measure current, voltage and power factor. As key features, the NIWEM is completely non-invasive and it can self-sustain its operations by harvesting energy from the monitored load. It also features a standard (Zigbee) wireless interface for communication with the smart-building system. Experimental results have confirmed that complete energy sustainability can be achieved also with very low-power loads.