Doctoral Defense

Non-Contact Instrumentation of Energy Flow for the Modern Distribution Grid

Joseph G. Cheang

August 2, 2019
11:00 AM
Light Engineering room 250
Advisor: Michael Gouzman

Concerns over the stability of the electric grid are often preceded by discussions regarding the increasing rate of distributed energy resource (DER) installations. Depending on the level of DER penetration, the effects of local system volatilities may not be fully represented by upstream monitoring and control equipment. If a holistic view is required, then investigating the local interaction of DER at each service transformer is needed. However, due to the sheer number of local nodes, this task is often impractical using traditional methods.

It’s our position, that developing a new sensor system with the capability of automated deployment would be more practical. The key to automated deployment is simplifying the device’s installation process onto powerlines. Therefore, non-contact voltage and current transducers are the essential components in the design. After reviewing several non-contact transducer technologies, this dissertation focuses on the design and application of a free-bodyprobe and an instrumental current transformer to ascertain the powerline’s voltage and current signals. Using Poynting theorem, the direction of power flow was computed from the transducers’ output signals via analog and digital methods. To validate the prototypes’ non-contact capabilities, a single phase 120Vac 60Hz powerline with grid-tie inverters and a load was created in the laboratory. The setup simulated a distribution feeder with DER that allowed us to observe the prototypes’ responses as the power flow was adjusted by varying the DER and or load.

The devices were able to determine the direction of power flow for loads above 0.5Watts. With the digital method, an HMI was built in MATLAB that provided additional functions like oscillography, calibration, and frequency magnitude response. Although the prototypes were only tested on low voltage lines, both transducers are scalable for high voltage applications. Further studies on the accuracy and limitations of the free-body-probe based electric field transducer designed in this dissertation is slated for future work.