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Choice of disconnector
Lightning
protection
Dimensions
Section 10
9
Choice of disconnector
The disconnector is necessary to ensure the safety of the installation
b
b
One of the surge arrester parameters is the maximum current (Imax 8/20 µs wave)
that it can withstand without degradation. If this current is exceeded, the surge
arrester will be destroyed; it will be permanently short circuited and it is essential
to replace it.
The fault current must therefore be eliminated by an external disconnector installed
upstream.
The disconnector provides the complete protection required by a surge arrester
installation, i.e.:
v
v
It must be able to withstand standard test waves:
-- It must not trip at 20 impulses at In
-- It can trip at Imax without being destroyed
v
v
The surge arrester disconnects if it short-circuits.
b
b
The ready-to-cable surge arresters with an integrated disconnection circuit
breaker are:
v
v
Combi PRF1
v
v
Quick PF
v
v
Quick PRD.
Surge arrester / disconnection circuit breaker correspondence table
Types Isc
Surge arresters
6 kA 10 kA 15 kA 25 kA 36 kA 50 kA 70 kA
Type 1
35 kA
(1)
PRF1 Master
NH 160 A gL/gG fuse
NS160N
160 A
NS160H
160 A
25 kA
(1)
PRF1
D125
NH 125 A gL/gG fuse
Type 2
65 kA
(2)
PF65, PRD65
C60N
50 A
Curve C
C60H
50 A
Curve C
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40 kA
(2)
PF40, PRD40
C60N
40 A
Curve C
C60H
40 A
Curve C
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20 kA
(2)
PF20, PRD20
C60N
25 A
Curve C
C60H
25 A
Curve C
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8 kA
(2)
C60N
20 A
Curve C
C60H
20 A
Curve C
Isc: prospective short-circuit current at the point of installation.
(1) Iimp.
(2) Imax.
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