yes army cadets are authorised to wear the combat green chevrons, provided that thew are sewn onto the combat green armlet and worn on the right arm (since it is the same arm army cadet ranks are worn)
also, you must have a clear badge identifying you as a cadet. such as the Royal Canadian Army Cadet badge.
some corps also allow things like their affiliated unit badge or patch on the armlet. For example, on my combat armlet, i have the Royal Canadian Army Cadet badge at the top, a Hunting Stewart tartan patch below that, and my combat rank below that. the tartan patch represents the Canadian Scottish Regiment (Princess Mary's), which is the affiliated unit