An Optical Voltage Sensor Based on Piezoelectric Thin Film for Grid Applications

TL;DR

This paper introduces a compact optical voltage sensor using piezoelectric thin film for power grid monitoring, offering advantages over traditional bulky transformers in terms of size, cost, and environmental robustness.

Contribution

The authors developed a millimeter-sized optical voltage sensor based on AlN thin film that enables continuous AC voltage measurement with high accuracy and low power consumption, addressing limitations of existing transformers.

Findings

Achieved a resolution of 170mVrms at 5kHz bandwidth

Sensor operated with 110μW optical power from a low-cost LED

Maintained measurement accuracy within 0.04% over 20-60°C temperature range

Abstract

Continuous monitoring of voltages ranging from tens to hundreds of kV over environmental conditions, such as temperature, is of great interest in power grid applications. This is typically done via instrument transformers. These transformers, although accurate and robust to environmental conditions, are bulky and expensive, limiting their use in microgrids and distributed sensing applications. Here, we present a millimeter-sized optical voltage sensor based on piezoelectric aluminum nitride (AlN) thin film for continuous measurements of AC voltages <350kVrms (via capacitive division) that avoids the drawbacks of existing voltage-sensing transformers. This sensor operated with 110uW incident optical power from a low-cost LED achieved a resolution of 170mVrms in a 5kHz bandwidth, a measurement inaccuracy of 0.04% due to sensor nonlinearity, and a gain deviation of +/-0.2% over the temperature range of ~20-60C. The sensor has a breakdown voltage of 100V, and its lifetime can meet or exceed that of instrument transformers when operated at voltages <42Vrms. We believe that our sensor has the potential to reduce the cost of grid monitoring, providing a path towards more distributed sensing and control of the grid.