Siemens ISI EN 50295 - Manual (Page 103)

Siemens IK PI · 2004 6/103
AS-Interface Slaves
Modules with special functions
Overvoltage protection module
6
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Overview
The AS-Interface overvoltage protection module protects down-
stream AS-Interface devices or individual sections of the instal-
lation in AS-Interface networks from conducted overvoltage
caused by switching procedures and distant lightning strikes.
The installation site of the overvoltage protection module repre-
sents the transition from Zone 1 to 2/3 within the lightning protec-
tion zone concept. Direct lightning strikes must be overcome by
means of additional protective measures at the transitions from
lightning protection Zone 0A to 1.
The AS-Interface overvoltage protection module enables the AS-
Interface to be integrated into the overall overvoltage protection
concept of a plant or machine.
The module has the same design, connection and degree of
protection (IP67) as the previous AS-Interface application mod-
ules. It is a passive module without an AS-i IC and therefore does
not require its own address on the AS-Interface network.
It is connected to an AS-Interface system via the FK-E or PG-E
coupling module. The EEMS interface can be used to protect the
AS-Interface cable and the auxiliary voltage cable against over-
voltage.
Overvoltages are diverted via a ground cable with a yel-
low/green oil-proof outer casing. This cable is permanently inte-
grated into the module and must be connected to system earth
with a low resistance connection.
Nominal discharge current i
sn
The nominal discharge current is the peak value of a peak cur-
rent with an 8/20 microsecond waveform for which the overvolt-
age protection module is rated in accordance with a specific test
program.
With the 8/20 waveform, 100% of the value is reached after
8 microseconds and 50% of the value is reached after 20 micro-
seconds.
Protection level U
p
The protection level of an overvoltage protection module is the
highest instantaneous voltage value at the terminals which is
determined from individual tests.
The protection level characterizes the capability of an overvolt-
age protection module to limit overvoltages to a residual level
Accessories
An FK-E or PG-E coupling module is required to connect the
AS-Interface cable and the auxiliary voltage supply cable.
Installation guidelines
Earthing of the protective modules and of the devices to be
protected must be carried out via a common grounding point
(equipotential bonding). If devices with total insulation are to be protected, their mounting brackets must also be connected into
the grounding points.
Application example
NSA0_00093 AS-
Inter-
face AS-
Inter-
face
Application
Device without earth connection
® Earthing of the mounting plate
Mounting plate Device with
earth connection
Application
OVP
OVP = Overvoltage protection
A S -
I n t e r -
f a c e
N S A 0 _ 0 0 0 9 2
A
A S -
I n t e r -
f a c e
B
A S -
I n t e r -
f a c e A S -
I n t e r -
f a c e
Z o n e 2
p r o t e c t e d r a n g e
E q u i p o t e n t i a l b o n d i n g
( s y s t e m e a r t h )
Z o n e 1 Z o n e 1
P r o t e c t i o n a p p r o x . 0 . 5 m t o t h e l e f t
P r o t e c t i o n a p p r o x . 5 m t o t h e r i g h t
O V P O V P
O V P = O v e r v o l t a g e p r o t e c t i o n