Additional means of protection for single fault conditions
Accessible parts shall be prevented from becoming HAZARDOUS LIVE IN
SINGLE FAULT CONDITION. The primary means of protection (see
Figure 2.2) shall be supplemented by one of
A
,
B
,
C
or
D
. Alternatively, one of
the single means of protection
E
or
F
shall be used. See Figure 2.2.
B
A
A
C
C
D
E
F
B
BASIC
INSULATION
ENCLOSURE or
BARRIER
IMPEDANCE
REINFORCED
INSULATION
PROTECTIVE
IMPEDANCE
SUPPLEMENTARY
INSULATION
PROTECTIVE
BONDING (or
SCREEN)
AUTOMATIC
DISCONNECTION
of the SUPPLY
CURRENT- or
VOLTAGE-LIMITING
DEVICE
HAZARDOUS PART
ACCESSIBLE PART
and
DOUBLE INSULA
TION
Figure 2.2:
Acceptable arrangement of protective means against electric shock
Example: A measurement device is specified as 600 V CAT II reinforced
insulation, with a maximum input voltage 1000 V DC.
Using the information above, it can be concluded that this specification informs
the user that the measurement device is tested on input to chassis ground for
five seconds at 3510 V RMS and impulse 6400 V. The maximum operating input
voltage is 1000 V DC. This device is to be used to measure CAT II circuitry up
to 600 V.
GEN3t
I3995-3.1 en HBM: public
31