ERICO TDS-MOVTEC Surge Diverters - Manual (Page 12)

G L O B A L L I G H T N I N G T E C H N O L O G I E S
PAGE 12
against sustained over-voltage conditions
where the supply voltage exceeds the protection
equipment’s nominal rating for an extended
period of time, ie continuous over-voltages
from poorly regulated generators or
distribution systems.
Smaller power generation equipment
(particularly capacitive excitation induction
generators) does not generally conform to the
same standards of voltage regulation that are
in place for mains power reticulation. A large
number of smaller and/or cheaper generators
have a voltage waveform that is “loosely”
240Vrms (often poorly regulated), but more
importantly, often contains significant higher
order harmonics. These generators may
exhibit a peak voltage on each half cycle far in
excess of the normal 340V. The problem is
usually worse when the generator is lightly
loaded.
Whilst electrical equipment may tolerate this
over-voltage for a period of time, the clamping
elements in the power protection devices will
begin to conduct on the peak of each 50Hz
cycle, as their voltage threshold is reached
(typically 400V peak for a traditional 275V
diverter). This will cause slow degradation
and ultimate failure of the clamping device
(time dependent upon how poor the waveform
is).
Harmonic voltages may also be present in
distribution systems that do not feature
generators. This is normally where non-linear
loads are used, such as UPSs, rectifiers,
switch mode power supplies and motor speed
controls. The high harmonic voltages in
certain applications may have peak voltages
in excess of the protective clamping voltage
causing problems as described above. Seek the
manufacturer’s advice before installing any