Active Member
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[China]
Address: 618, Goodbond Venture Base, No.18, Lu Yun Road, Yue Lu District, Changsha City, Hunan Province
Contact name:cody
Hunan Heou Engineering Consulting Co., Ltd |
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Lightning protector is an indispensable device in the lightning
protection of electronic equipment, its role is to flee into the
power lines, signal transmission lines of transient overvoltage
limit in the equipment or system can withstand the voltage range,
or will be a strong lightning current discharge into the ground, in
order to protect the protected equipment or system from the impact.
Divided by working principle
According to its working principle, SPD can be divided into voltage
switching type, voltage limiting type and combination type.
(1) Voltage switching type SPD, presenting high impedance when
there is no transient overvoltage, once responding to lightning
transient overvoltage, its impedance will suddenly change to low
impedance, allowing lightning current to pass through, also known
as "short-circuit switching type SPD".
(2) voltage limiting SPD. when there is no transient overvoltage,
the impedance is high, but with the increase in surge current and
voltage, its impedance will continue to decrease, its current and
voltage characteristics have a strong nonlinearity, sometimes
referred to as "clamp type SPD.
(3) combined SPD. by the combination of voltage-switching type
components and voltage-limiting type components, can behave as a
voltage-switching type or voltage-limiting type or both, depending
on the characteristics of the applied voltage.
Power SPD
Because the energy of a lightning strike is very large, it is
necessary to gradually release the lightning energy to earth
through a graded discharge method. In the direct lightning
non-protected area (LPZ0A) or in the direct lightning protection
zone (LPZ0B) and the first protection zone (LPZ1) junction, the
installation of surge protectors or voltage limiting surge
protectors through the first level of classification test as the
first level of protection, the direct lightning current discharge,
or when the transmission line suffers a direct lightning strike,
will conduct a huge amount of energy for discharge. In the first
protection zone after the partition (including LPZ1 zone) junction
of the installation of voltage limiting surge protector, as the
second, third or higher level of protection. The second level
protector is for the residual voltage of the first level protector
and induction lightning strikes in the area of protection
equipment, in the first level to absorb the larger lightning strike
energy, there are still some equipment or the third level protector
energy is quite huge, will be conducted over, the need for the
second level protector to further absorb. At the same time, the
transmission line through the first level of lightning protector
will also induce lightning strike electromagnetic pulse radiation.
When the line is long enough, the induced lightning energy becomes
larger, requiring the second-stage protector to further implement
the discharge of lightning strike energy. The third level protector
protects the residual lightning energy that passes through the
second level protector. Depending on the voltage level of the
equipment being protected, if the two-stage lightning protector can
limit the voltage to below the voltage level of the equipment, only
two levels of protection are required; if the voltage level of the
equipment is lower, four or more levels of protection may be
required.
To choose SPD, you need to understand some parameters and its
working principle first.
(1) 10/350μs wave is the waveform of simulated direct lightning,
waveform energy; 8/20μs wave is the waveform of simulated lightning
induction and lightning conduction.
(2) The rated discharge current In is the peak current flowing
through the SPD, 8/20μs current wave.
(3) Maximum discharge current Imax, also known as the maximum flux,
is the maximum discharge current that can be withstood at one time
using the 8/20μs current wave to impact the SPD.
(4) The maximum continuous withstand voltage Uc (rms) is the
maximum AC voltage RMS or DC voltage that can be continuously
applied to the SPD.
(5) Residual voltage Ur is the residual voltage value at the rated
discharge current In.
(6) Protection voltage Up characterizes the voltage characteristic
parameter between the SPD limiting terminals, the value of which
can be selected from the list of preferred values and should be
greater than the maximum value of limiting voltage.
(7) The voltage switching type SPD mainly discharges a current wave
of 10/350μs, while the voltage limiting type SPD mainly discharges
a current wave of 8/20μs.
