Introduction and Specifications
General Safety Summary 1
1-7
Description of IEC 61010 Measurement Categories
The IEC 61010 safety standard defines four Overvoltage (Installation) Categories (CAT I
to CAT IV) based on the magnitude of danger from transient impulses as shown in Figure
1-1.
Service
Entrance
Meter
Meter
Service
Entrance
Meter
Outbuilding
Outbuilding
Transformer
Underground Service
Underground Service
CAT I
Electronic
CAT II
Appliances,
PCs, TVs
CAT III
MC Panels, etc.
CAT IV
Service
Entrance
cat_levels.eps
Figure 1-1. IEC 61010 Measurement Category (CAT) Levels
The IEC 61010 Measurement CAT level indicates the level of protection the instrument
provides against impulse withstand voltage.
CAT I equipment is designed to protect against transients from high-voltage, low-energy
sources, such as electronic circuits or a copy machine.
CAT II equipment is designed to protect against transients from energy-consuming
equipment supplied from the fixed installation, such as TVs, PCs, portable tools, and
other household appliances.
CAT III equipment is designed to protect against transients in equipment in fixed
equipment installations, such as distribution panels, feeders and short branch circuits, and
lighting systems in large buildings.
CAT IV equipment is designed to protect against transients from the primary supply
level, such as an electricity meter or an overhead or underground utility service.
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