| Summary: | This dissertation presents the concept of a small, low-cost, self-powered smart
wireless sensor that can be used for monitoring current, temperature and voltage on a
variety of utility assets. Novel energy harvesting approaches are proposed that enable the
sensor to operate without batteries and to have an expected life of 20-30 years.
The sensor measures current flowing in an asset using an open ferromagnetic core,
unlike a CT which uses a closed core, which makes the proposed sensor small in size, and
low-cost. Further, it allows the sensor to operate in conjunction with different assets
having different geometries, such as bus-bars, cables, disconnect switches, overhead
conductors, transformers, and shunt capacitors, and function even when kept in the
vicinity of an asset. Two novel current sensing algorithms have been developed that help
the sensor to autonomously calibrate and make the sensor immune from far-fields and
cross-talk. The current sensing algorithms have been implemented and tested in the lab at
up to 1000 A.
This research also presents a novel self-calibrating low-cost voltage sensing
technique. The major purpose of voltage sensing is detection of sags, swells and loss-ofpower
on the asset; therefore, the constraint on error in measurement is relaxed. The
technique has been tested through several simulation studies. A voltage sensor prototype
has been developed and tested on a high voltage bus at up to 35 kV.
Finally, a study of sensor operation under faults, such as lightning strikes, and large
short circuit currents has been presented. These studies are conducted using simulations
and actual experiments. Based on the results of the experiments, a robust protection
circuit for the sensor is proposed. Issues related to corona and external electrical noise on
the communication network are also discussed and experimentally tested. Further, optimal
design of the energy harvester and a novel design of package for the sensor that prevents
the circuitry from external electrical noise without attenuation of power signals for the
energy harvester are also proposed.
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