Siemens Simatic 6ES7 157-0AC80-0 A0 Series, Manual

Page: 118 / 182

Fundamentals of PROFIBUS-PA
A-2
DP/PA Link and Y Link Bus Couplings
A5E00193841-011
A.1 Intrinsic safety
Intrinsic safety
The intrinsic safety type of ignition protection is based on the fact that a certain
minimum ignition energy is required to ignite an explosive atmosphere. In an
intrinsically safe electric circuit, this minimum ignition energy does not exist in the
explosion-proof area either during normal operation or in the event of a
malfunction. The intrinsic safety of a circuit is achieved by limiting the current and
voltage in order to prevent sparking and high temperatures as possible ignition
sources. The intrinsic safety type of ignition protection is thus limited to circuits with
relatively low performance.
Spark ignition
The so-called spark ignition is eliminated because sparks, which usually occur
when a circuit is opened and closed either during operation or in the event of a
short circuit or ground fault, are ruled out by limiting the current and voltage and
avoiding large inductivities.
Thermal ignition
Thermal ignition is not possible either during normal operation or in the event of a
malfunction, since the equipment and lines in the intrinsically safe circuit cannot
overheat.
Further information
You will find further information on the subjects of intrinsic safety and explosion
protection in the following publications:
The manual entitled Automation Systems S7-300, M7-300, ET 200M Ex-I/O
Modules (Order no. 6ES7 398-8RA00-8xA0)
PTB report W-53, Brunswick, March 1993 (Investigations into the intrinsic
safety of field bus systems)
PROFIBUS-PA Installation guide,
Information on the use of IEC 1158-2 technology for PROFIBUS,
(German Art. No. 2.091, English Art. No. 2.092)
PROFIBUS-Nutzerorganisation e. V.,
Haid-und-Neu-Straße 7, D-76131 Karlsruhe
On the Internet under
www.profibus.com