I think not. The "why not" is that it means different things to different sectors of the industry. In my world, "LV" is below 120 VAC, and applies to fire alarm, security, and similar systems. I use "MV" for anything above 480 VAC, up to 25,000 VAC or so, and "HV" for anything higher. But a person who works with fire alarm systems might consider 120 VAC to be "high voltage." So whenever I hear or read someone's use of these terms, I make sure to verify what that person means by the terms, before proceeding.
Charles E. Beck, P.E., Seattle
Comments based on 2008 NEC unless otherwise noted.