Part - Leutron GmbH

Power Engineering
Class I+II (T1+T2) Combined Arresters
IsoPro BC, TN-C, TN-S and TT Systems
• Completely mounted on busbar, ready-to-connect
• Discharge capacity up to 100 kA (10/350 µs)
• High insulation resistance
• Protection level ≤ 2 kV
• V-wiring with multi-functional terminals
• On the basis of hermetically sealed rare-gas-filled
spark gaps
• No blow-out vents, thus, not requiring any safety
clearance to other installations
• No leakage currents, thus, allowing installation
upstream of power meters
• Optional remote signalling contact (FM) requiring no
additional space
Multi-pole combined modular arresters for the protection of
low-voltage consumers’ installations in industrial, business
and residential areas against surges caused by lightning or
switching actions in the network.
The arresters can be installed at the transition 0 A to 2 according
to the lightning protection zones concept.
The series IsoPro (IP) is based on a well-proved technology.
Per pole two selectively responding protection stages are
placed in a combined DIN housing (2 MW of only 35 mm). The
leakage current-free protective circuit consists of a varistor
(MOV) and a gas-filled surge arrester (GDT) connected in series.
In addition, a rare-gas-filled, hermetically sealed highperformance
isolating spark gap from industrial ceramics
– resistant against pressure and high temperatures – is connected
in parallel.
The IsoPro BC combined modular arrester is available with a
discharge capability of 25 kA and 60 kA (10/350 µs) per pole,
or at TT systems with 100 kA (10/350µs) between N and PE.
Due to the application of the gas discharge technology the
IsoPro BC SPDs are resistant against temporary and long lasting
overvoltages (TOV) up to 500 V (50 Hz).
Therefore, the SPDs of the series IsoPro can confidentially
be applied at all protection levels according to DIN EN 62305
(VDE 0185-305).
This SPD has a redundant function. In case of a (theoretically
possible) malfunction of the first protection stage the robust
and overload-resistant main spark gap remains in operation
and guarantees the coarse protection of the network.
High-energy lightning impulse currents cause the main spark
gap to fire, thus, protecting the first protection stage (MOV
and GDT) against thermal overload.
Only the first protection stage responds during occurring
transient surges of low energy. The main spark gap will not
fire. Due to the limiting behaviour of the MOV varistor the response
of the first protection stage will not result in a short
circuit and, therefore, in no follow-on short-circuit current.
The back-up fuse will not actuate in this case.
The main spark gap extinguishes follow-on short-circuit currents
only under certain conditions. If a maximum operational
availability is desired, a back-up fuse of ≤ 160 A is necessary
to extinguish a firing main spark gap and, thus, preventing
it from thermal damage. In most cases a back-up fuse will
be installed in industrial applications and for maintenance
reasons, whereby the power supply will not be interrupted
even if the SPD fails.
Lightning impulse currents with a high energy content cause
the main spark gap to fire immediately after the triggering
of the first protection stage. Hence, the main spark gap with
its discharge capacity unloads the first stage and protects it
against damage.
With back-up fuses or circuit-breakers of more than 160 A a
selective back-up fuse (fusible cutout) of a maximum of 160 A
has to be installed to avoid an overload of the IsoPro caused
by a high short-circuit current.
Combined modular arresters of the series BC offer a higher
insulation level and lower investment and installation costs,
due to their low residual voltage. They are able to divert high
lightning impulse currents and operate also at small, transient
44 Leutron GmbH · Humboldtstrasse 30 · 70771 Leinfelden-Echterdingen · Germany · Phone +49 711 94771-0 · www.leutron.de