  Micro-Phasor Measurement Units (u-PMUs) are devices that permit monitoring
voltage and current in the distribution grid with high accuracy, thus enabling
a wide range of smart grid applications, such as state estimation, protection
and control. These devices need to transmit the synchronous measurements of
voltage and current, also known as synchrophasors, to the power utility control
center at high rate. The use of wireless networks, such as LTE, to transmit
synchrophasor data is becoming increasingly popular. However, synchrophasors
are included in small frames and it would be more efficient to use low power
cellular solutions, such as LTE cat-M. In this work, we present experimental
research on the deployment of a u-PMU with the ability to connect over a
commercial LTE cat-M network. The deployed u-PMU is built with off-the-shelf
hardware, such as Arduino microcontrollers, and is used to transmit
data-compliant with the IEEE C37.118.2 standard at a variable rate from 1
frame/s to 80 frames/s. A detailed network performance analysis is carried out
to show the suitability of LTE cat-M to support u-PMU communications.
Experimental results on performance indicators, such as delay and jitter, are
reported. The effect of the LTE cat-M access mechanism on the time distribution
of frame arrivals is also thoroughly analyzed.
