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Third level of protection
The purpose is the ultimate means of protecting equipment, the
value of the residual surge voltage is reduced to within 1000V, so
that the energy of the surge does not damage the equipment.
In the electronic information equipment AC power inlet end of the
power supply lightning protector installed as the third level of
protection should be series-limited power supply lightning
protector, the lightning through-current capacity should not be
less than 10KA.
The last line of protection can be used in the internal power
supply part of the power equipment with a built-in power supply
lightning arrester, in order to completely eliminate the purpose of
the small transient overvoltage. The power supply lightning
arrester used there requires a maximum impact capacity of 20KA per
phase or less, and the required limiting voltage should be less
than 1000V. For some particularly important or sensitive electronic
equipment with the third level of protection is necessary, but also
to protect power-using equipment from the transient overvoltage
generated within the system.
For microwave communication equipment, mobile station communication
equipment and radar equipment, such as the use of rectifier power
supply, depending on its working voltage protection needs are
appropriate to choose the working voltage of the appropriate DC
power lightning arrester as the last level of protection.
Fourth level and above
According to the voltage level of the protected equipment, if two
levels of lightning protection can be done to limit the voltage
below the level of the equipment, only two levels of protection are
required, if the level of voltage resistance of the equipment is
low, it may require four or more levels of protection. The fourth
level of protection should have a lightning through-current
capacity of not less than 5KA.[3]
Installation Method Editor Podcast
SPD conventional installation requirements
Surge protector using 35MM standard rail installation, for fixed
SPD, conventional installation should follow the following steps [1
1) Determine the discharge current path
(2) mark the additional voltage drop caused by the wire at the end
of the equipment,.
3) To avoid unnecessary induction loops, the PE conductor of each
device should be marked.
4) to establish an equipotential connection between the equipment
and the SPD.
5) To carry out energy coordination of multi-level SPD
In order to limit the inductive coupling between the protected part
of the installation and the unprotected part of the equipment,
certain measurements need to be made. Through the separation of the
induction source and sacrificial circuit, the selection of the
circuit angle and the limitation of the closed circuit area can
reduce mutual inductance, when the current-carrying component
conductor is part of the closed circuit, due to the proximity of
this conductor to the circuit and the induced voltage and reduce.
In general, it is better to separate the protected conductor from
the unprotected conductor, and, moreover, should be separated from
the ground wire. Also, in order to avoid transient quadrature
coupling between the power cable and the communication cable, the
necessary measurements should be made.
SPD grounding wire diameter selection
Data line: requires greater than 2.5mm²; when the length exceeds
0.5m requires greater than 4mm². yd/t5098-1998.
Power line: phase line cross-sectional area S ≤ 16mm², ground with
S; phase line cross-sectional area 16mm2 ≤ S ≤ 35mm², ground with
16mm²; phase line cross-sectional area S ≥ 35mm², the ground
requires S/2; GB 50057 section 2.2.9 [3]