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I L I L
1 1‘ 1 1‘
BLITZDUCTOR XT ITE
2 2‘
I L I L

2 2‘ Figure 8.2.9 Nominal current of BLITZDUCTOR XT

Type I L at 45 °C Type I L at 45 °C
B 1.2 A
BE 0.75 A / 1 A BD 0.75 A / 1 A
current I sn
BC 0.75 A / 1 A BE C 0.1 A
Figure 8.2.7 Test setup for determining the limiting voltage in case BE HF 1 A BD HF 1 A
of nominal discharge currents
MY 3 A BD DL S 0.4 A
BD EX 0.5 A
BD HF EX 4.8 A
U in V limiting voltage
60 Table 8.2.2 Maximum nominal currents of the BXT protection
modules
40
20
0 f G f in Hz
- 20 3 dB
- 40
- 60
0 10 20 30 40 50 60 70 80 90 100
t in µs a E in dB

Figure 8.2.8 Limiting voltage in case of nominal discharge currents Figure 8.2.10 Typical frequency response of a BLITZDUCTOR XT

Limiting voltage in case of nominal discharge Cut-off frequency f G
currents The cut-off frequency describes the frequency-dependent be-
This test is carried out to determine the limiting behaviour haviour of an arrester. The cut-off frequency is the frequency
of protection elements with constant limiting characteristics which causes an insertion loss (a E ) of 3 dB under certain test
(Figures 8.2.7 and 8.2.8). conditions (see IEC 61643-21 (EN 61643-21)) (Figure 8.2.10).
Unless specified otherwise, the specified frequency refers to a
Nominal current I L 50 ohm system.
The nominal current of BLITZDUCTOR XT characterises the per-
missible operating current of the measuring circuit to be pro- Selection criteria (SC)
tected. The nominal current of BLITZDUCTOR XT is determined 1. Which discharge capacity is required?
by the current carrying capability and the insertion loss of the The discharge capacity of BLITZDUCTOR XT depends on the
impedances used for decoupling between the gas discharge protective task the arrester must fulfil. To facilitate selection,
tubes and fine protection elements as well as by the follow the following cases a to d are explained.
current extinguishing capability of the gas discharge tubes. The
nominal current is stated as d.c. value (Figure 8.2.9). Case a
Examples of the maximum nominal currents of the individu- In this case, the terminal device to be protected is located
al BLITZDUCTOR XT protection modules are listed in Table in a building with an external lightning protection system or
8.2.2. the roof of the building is equipped with metal roof-mounted

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