SIEMENS
7/153
Siemens IK PI · 2015
Industrial Remote Communication
Accessories for remote networks
LTOP overvoltage protection
7
■
Overview
•
Line transformer with overvoltage protection
•
For electrical isolation of a dedicated line modem from the
trunk line
•
For protection against overvoltages that can be injected into a
trunk line
■
Benefits
•
Reduces overvoltage to tolerable levels before they reach
sensitive electronics circuits
•
Electrically isolates line sections; prevents interference due
to external voltages
•
Limits damage to segments affected by overvoltage
•
The protective components are housed in a plug-in OPM
overvoltage module. The OPM can be replaced without
interrupting the trunk line.
■
Application
Dedicated copper lines are susceptible to electromagnetic inter-
ference. The coupling of extraneous voltages can be inductive
or capacitive, for example due to the effects of lightning. Direct
conductive coupling is also possible due to bad insulation.
The LTOP overvoltage protection limits external voltage and
overvoltage to a non-critical level. The floating transformer
additionally provides electrical isolation, and the transfer of
voltages to other cable sections are therefore prevented.
LTOP protects people and investments, and is therefore an
essential safety element in private trunk line networks.
Note:
The LTOP modules are not
suitable for protecting dial-up
connections (telephone or ISDN network). Companies such as
Phoenix and Dehn offer TAE6, S
0
, RJ-12, and RJ-45 jacks with
overvoltage protection.
■
Design
The protection concept consists of a combination of compo-
nents that complement each other in terms of functionality:
•
Surge arresters filled with noble gas as coarse protection
(G1, G2)
•
Inductance that limits the rise of the current (L1, L2)
•
Metal-oxide varistor as surge protection (voltage-dependent
resistor; R1)
•
Translator for galvanic decoupling (T1)
•
Suppressor diode for limiting the secondary voltage of the
translator (V1)
The overvoltage protection module LTOP is available in two
variants:
•
LTOP 1;
overvoltage protection module for use at the beginning or at
the end of a 2-wire cable
•
LTOP 2;
overvoltage protection module for use at the beginning or
at the end of a 4-wire cable or at a 2-wire grading point. At a
4-wire graded point, two LTOP2 units are needed.
Both LTOP variants feature screw-type terminals and an RJ12
Western jack. The WAN connecting cable (RJ12 - RJ12) that
came with the MD2 and MD3 modems (used as dedicated line
modem) can be connected directly to this RJ12 jack.
© Siemens AG 2014