Noncontact Power Sensing

Technology

This non-intrusive power monitoring apparatus provides circuit information without coming in contact with the circuit. The apparatus comprises a capacitive pickup, circuitry for sensing a signal from the pickup, an Analog to Digital Converter, and a digital filter that rejects low-frequency disturbances. The sensor’s design allows an untrained user to place the device in a suitable position to measure a physical parameter (electric or magnetic field) produced by existing installed equipment. In order to maximize the dependence of gain on plate-to-wire distance, the system takes a differential measurement of two vertically stacked sensor plates. Doing so neatly selects the signal from a nearby wire and rejects signals from distant wires. The circuitry of the sensor is optimally designed to be fast enough to respond to the fluctuations in monitored power and strong enough to obtain usable voltage signals out of the amplifier.

Problem Addressed

Reducing utility customer power consumption could lead to improvements in greenhouse gas emissions. With the help of power monitoring information, a smart grid can allow customers to capitalize on energy savings. Centralized power monitoring systems identify and monitor loads according to their current signatures. These systems employ closed or clamp core sensors to provide current sense signals, which are impractical in many retrofit applications. Firstly, skilled labor is required to separate line and neutral in order to deploy a wrap-around sensor, and secondly, in some industrial environments electrical service interruption may be unacceptable or prohibitively expensive. Non-contact power monitoring addresses both of these problems, but current solutions require replacement of the existing circuit breaker. As a result, there is a significant increase in cost on the consumer end.

Advantages

• Easy installation does not require a hired technician
• Enables power monitoring without altering circuit
• Lower cost, more sensitive, and more robust sensor because of integrated capacitive pickups

Publications

Aboulian, A. et al. "NILM Dashboard: A Power System Monitor for Electromechanical Equipment Diagnostics," IEEE Transactions on Industrial Informatics 15, no. 3 (March 2019): 1405-1414. doi: 10.1109/TII.2018.2843770.