Datasheet

II-2015, www.findernet.com
24
E
7P SERIES
Surge Protection Device (SPD)
7P
SERIES
Rated values and marking common to all SPD
[U
C
] Maximum continuous operating voltage: Under this voltage the
SPD is guaranteed to appear as an “open switch”. This voltage is normally
at least equal to the nominal supply voltage (U
N
) +10%. For the Finder SPD,
U
C
is specified as 275V.
[U
p
] Voltage protection level: This is the highest voltage level seen across
the SPD during its intervention. For example, for Finder SPD Type 2, this
means that a 4kV overvoltage would be limited by the SPD to a maximum
1.2 kV. Consequently, electronic devices such as PC, TV, stereo, etc. are
protected - as their own internal protection will handle overvoltages U
p
to 1.5kV.
To better understand this concept; imagine that the SPD is a switch in
series a low resistance. In the case of an overvoltage the switch closes and
all the current goes through the resistance. According to Ohm’s law the
voltage developed across the resistance will be this resistance x the current
(V=RxI), and will be limited to <U
p
.
Figure 4: Overvoltage limiting
Short circuit proof: A further characteristic, not normally marked on the
product but important for its correct installation, is the Short circuit proof
at maximum overcurrent protection. This is the maximum short-circuit
current that the SPD is able to withstand when it is installed with additional
maximum overcurrent protection - such as a fuse rated in accordance with
the value stated under the SPD specification. Consequentely the maximum
prospective short-circuit current of the system at the point of installation
of the SPD must not exceed this value.
Rated vaules and marking of SPD Type 1
SPD Type 1 must be connected upstream the system, at the point of
delivery of power energy. SPD protects building and people from the risk
of direct lightning (fire and death) and are characterized by:
[I
imp
10/350] Impulse current: I
imp
corresponds to the peak value of a
10/350 μs current impulse waveform. This waveform represents a direct
lightning strike and is used in tests to prove the performance of SPD type
1 devices.
Figure 5: 10/350μs current waveform
Comparison of the waveforms in figures 5 and 6 shows the much higher
energy content controlled by the type 1 SPD.
[I
n
8/20] Nominal discharge current: The peak current (and waveform
shape) through the SPD under conditions prescribed by EN 62305 to
represent the surge current as a consequence of a lightning strike to the
electric supply line.
I (peak)
Figure 6: 8/20μs current waveform
Rated values and marking of SPD Type 2
SPD Type 2 devices are designed to remove all the overvoltage from supply
circuits that are not likely to be directly hit by lightning. SPD Type 2 are
connected downstream SPD Type 1 or SPD Type 1+2, (minimum distance
1m) and they protect machine and tools connected to the ground and
reduce the risk of economic loss.
SPD Type 2 are characterized by:
[I
n
8/20] Nominal discharge current: The peak current (and waveform
shape) through the SPD under conditions prescribed by EN 62305 to
represent the surge current as a consequence of a lightning strike to the
electric supply line.
[I
max
8/20] Maximum discharge current: Peak value of the highest current
of a 8/20μs waveform that an SPD can discharge at least once without
breaking.
Rated values and marking of SPD Type 3
SPD type 3 devices are used to protect the end user from overvoltage.
They may be installed in supply networks where SDP types 1 and/or 2
already exist. They can be installed in fixed or mobile sockets and have the
following characteristic parameters.
U
oc
: test voltage. This is the peak value of the no load voltage of the
combined test-generator; this has a waveform of 1.2/50μs (figure 7) and
can supply at the same time current with waveform 8/20μs (figure 6).
Figure 7: 1.2/50μs voltage waveform
Suggestion for the connection
The correct connection of SPD requires a shortest as possible connection
to the local equipotential bar, to which are connected PE cables of the
equipment to be protected. From the local equipotential bar there is a
connection to the EBB. The phase wiring remains appropriate to the load.