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BETA Protecting
Overvoltage Protection Devices
Configuration
6/29
Siemens ET B1 · 10/2008
6
*
You can order this quantity or a multiple thereof.
Screening attenuation
Ratio of feeding power of a coaxial cable to that of the radiated
power of the cable supplied by the outer conductor
Series impedance
The impedance in signal flow direction between the input and
output of an arrester.
Short-circuit strength
The value of the prospective short-circuit current that can be controlled
by the overvoltage protection device if the respective back-up fuse
is connected.
Thermal isolating arrester
Overvoltage protection devices for power systems that are
equipped with voltage-dependent resistors (varistors) have an
integral isolating arrester, which disconnects the overvoltage
protection device from the mains in the event of an overload and
displays this operating state. The isolating arrester reacts to
"
joule heat" generated by an overloaded varistor and disconnects
the overvoltage protection device from the mains if a specific
temperature is exceeded. The isolating arrester disconnects the
overloaded overvoltage protection device from the mains so fast
that any risk of fire is prevented. However, it is not the task of an
isolating arrester to ensure "Protection against indirect contact".
Versions for Austria
The standard ÖVE/ÖNORM E 8001-1 is generally applied in Austria –
with pertinent additions.
The key difference for implementation of devices of type 2 is that
these have to have a higher rated voltage (335 V AC, 440 V AC).
Symbols
Switching symbol
Description
Overvoltage protection device
(
SPD: Surge Protection Device)
Lightning arresters, type 1
Surge arrester type 2 or type 3
Tripped spark gap
Varistors
Spark gap
Gas-filled surge arrester
Plug-in contact
Suppressor diode
© Siemens AG 2008