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Total Solution to Earthing & Lightning Protection |
9AKK106354A3360
10
Electronic systems protection
Introduction
Enhanced performance SPDs - SPD*
IEC/BS EN 62305-2 details the application of improved
performance SPDs to further lower the risk from damage.
The lower the sparkover voltage, the lower the chance
of flashover causing insulation breakdown, electric shock
and fire.
SPDs that offer lower let-through voltages further reduce
the risks of injury to living beings, physical damage as
well as failure and malfunction of internal systems.
All Furse ESP protectors offer such superior protection and
are termed as enhanced performance SPDs (SPD*) in line
with IEC/BS EN 62305.
Enhanced SPDs can also satisfy more than one test class/
category by handling both high-energy partial lightning
currents of 10/350 μs waveshape whilst offering very low
let-through voltages. Such enhanced SPDs may be
suitable for changing a lightning protection zone from LPZ
0
right through to LPZ 3 at a single boundary or installation
point. As such they provide both technical and
economic advantages over standard SPDs.
End of life
When an SPD comes to the end of its working life it should
not leave equipment unprotected. Thus in-line protectors
should take the line out of commission, preventing
subsequent transients from damaging equipment.
SPDs for data communication, signal and telephone lines and
protectors for low current mains power supplies are usually
in-line devices. Where SPDs are installed at mains power
distribution boards it is usually unacceptable for these to
suddenly fail, cutting the power supply.
Consequently, to prevent equipment being left unprotected,
the SPD should have a clear pre end-of-life warning,
which allows plenty of time for it to be replaced.
Installation
The performance of SPDs is heavily dependent upon their
correct installation. Thus, it is vital that SPDs are supplied with
clear installation instructions.
The following is intended to supplement the detailed guidance
given with each product in order to give a general overview
of installation. This should not be viewed as a substitute for
the Installation Instructions supplied with the SPD. Copies of
these are available separately on request.
Installing parallel connected SPDs for mains
power supplies:
–– SPDs should be installed very close to the power supply
to be protected, either within the distribution panel or
directly alongside of it (in an enclosure to the required
IP rating)
–– Connections between the SPD and phase(s), neutral and
earth of the supply should be kept very short (ideally 25 cm
or less, but no more than 50 cm)
–– SPD performance is further enhanced by tightly binding
connecting leads together (simply using cable ties or
similar), over their entire length
–– For safety and convenient means of isolation, the phase/
live connecting leads should be suitably fused using HRC
fuses or switchfuse, MCB or MCCB
Installing in-line SPDs for data, signal, telephone or power:
–– SPDs are usually installed between where cabling enters
or leaves buildings and the equipment being protected (or
actually within its control panel)
–– The installation position should be close to the system’s
earth star point (usually the mains power earth) to enable a
short and direct connection to earth
–– In-line, or series, connected SPDs generally have
connections marked line and clean. The line end of the
SPD should be connected to the incoming or “dirty” line
(from where the transient is expected). The clean end of
the SPD should be connected to the line or cable
feeding the equipment
–– Cables connected to the SPDs clean end should never be
routed next to dirty line cables or the SPDs earth bond
–– Unless ready-boxed, SPDs should be installed within an
existing cabinet/cubicle or in an enclosure to the
required IP rating