Voltage classifications

Electrical engineering terminology is rife with references to such voltages as MV (medium voltage), LV (low voltage) and HV (high voltage). It is often confusing and frequently misleading for new engineers to assess which is which. The problem is made more complicated by the fact there is no unanimous agreement among standard-making bodies regarding this classification. It is typical for an engineer in India to consider its own domestic network (240/415 V) as medium voltage (MV) while that in the U.S. (110 V) as LV. This is far from the truth. Any voltage less than 1 kV is LV according to all institutions making standards. The following table illustrates various categories in the table below.

Authority	Document/ clause ref.	LV	MV	HV
IEC	IEC 60269-1:2006 IEC 62271-200:2003	Less than 1 kV		1 kV to 52 kV
IEEE	IEEE 141:1983 Clause 3.1.1.2	Less than 1 kV	1 kV to 100 kV	100 kV to 230 kV
NEMA	NEMA C84.1:1995 Clause 2.1.3	Less than 1 kV	1 kV to 100 kV	100 kV to 230 kV
India	IS 10118-1:1982 Clause 5.1	Less than 1 kV		Above 1 kV
Shell	DEP 33.64.10.10 Clause 1.3.2	Less than 1 kV	1 kV to 36 kV	Above 36 kV