Electrical Interconnection In Explosion Hazardous Areas - ABB TTH300 Operating Instruction

5.3

Electrical interconnection in explosion hazardous areas

Depending on the safety requirements, special interconnections are required for use in
potentially explosive atmospheres.
Important
Refer to Chapter "Ex relevant specifications".
Intrinsic safety
The supply isolators / PCS inputs must feature intrinsically safe input protection circuits in order
to eliminate hazards (spark formation). The interconnection must be inspected. In order to
provide proof of intrinsic safety, the electrical limit values must be used as the basis for the EC-
type examination certificates for the equipment (devices); this includes the capacitance and
inductance values of the cables. Proof of intrinsic safety is said to have been provided if the
following conditions are fulfilled when a comparison is carried out in relation to the limit values of
the equipment:
Fig. 15
A Transmitter
OI/TTH300-EN
Transmitter
(intrinsically safe equipment)
U
i
I
i
P
i
L + L (cable)
i c
C + C (cable)
i c
Field (Ex area)
+
-
A
Supply isolator / PCS input
≥
≥
≥
≤
≤
B Supply isolator / PCS input with supply /
Segment coupler
TTH300
Electrical connections
(related equipment)
U
o
I
o
P
o
L
o
C
o
Control room (safe area)
+
-
B
A00096
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