Overvoltage Categories - Definitions - HT HT10 Manual De Instrucciones

1.4.

OVERVOLTAGE CATEGORIES - DEFINITIONS

IEC/EN61010-1 (Safety requirements for electrical equipment for measurement, control
and laboratory use, Part 1: General requirements) defines what a measurement category
(usually called "overvoltage category") is. At § 6.7.4: Measuring circuits it quotes: Circuits
are divided into the following measurement categories:
 Measurement Category IV is for measurements performed at the source of low
voltage installations.
Examples are electricity meters and measurements on primary overcurrent protection
devices and ripple control units
 Measurement Category III is for measurements performed in building installations.
Examples are measurements on distribution boards, circuit breakers, wiring, including
cables, bus-bars, junction boxes, switches, socket-outlets in the fixed installation and
equipment for industrial use and some other equipment, for example, stationary motors
with permanent connection to fixed installation.
 Measurement Category II is for measurements performed on circuits directly
connected to the low voltage installations.
Examples are measurements on household appliances, portable tools and similar
equipment.
 Measurement Category I is for measurements performed on circuits not directly
connected to MAINS.
Examples are measurements on circuits not derived from MAINS, and specially
protected (internal) MAINS-derived circuits. In the latter case, transient stresses are
variable; for that reason, the norm requires that the transient withstanding capability of
the equipment is made known to the user.
EN - 4
HT10