Short interruptions
The risk
Discharge lamps require a relighting time of a
few minutes after their power supply has been
switched off.
The solution
Partial lighting with instantaneous relighting
(incandescent lamps or fluorescent tubes)
should be provided if safety requirements so
dictate. Its power supply circuit is, depending on
current regulations, usually distinct from the main
lighting circuit.
Voltage fluctuations
The risk
The majority of lighting devices (with the
exception of lamps supplied by electronic
ballasts) are sensitive to rapid fluctuations in the
supply voltage. These fluctuations cause a
flicker phenomenon which is unpleasant for
users and may even cause significant problems.
These problems depend on both the frequency
of variations and their magnitude.
Standard IEC 61000-2-2 (“compatibility levels for
low-frequency conducted disturbances”)
specifies the maximum permissible magnitude of
voltage variations as a function of the number of
variations per second or per minute.
These voltage fluctuations can be caused by
high-power fluctuating loads (arc furnaces,
welding machines, starting motors) or remote
control signals (ie: Pulsadis, at 175 or 188 Hz
used by EDF -Electricité de France-).
The solution
Special methods can be used to reduce voltage
fluctuations. Nonetheless, it is advisable,
wherever possible, to supply lighting circuits via
a separate line supply.
The use of electronic ballasts that can be
controlled at 1-10 V is recommended for
demanding applications (hospitals, clean rooms,
inspection rooms, computer rooms, etc).
High line voltage
The risk
A high line voltage is responsible for reducing the
service life of incandescent lamps. This difficulty is
encountered in areas where the voltage regulation
provided by the energy distributor is inadequate.
The solution
Dimmers can be used, but are not a common
solution. The use of compact fluorescent lamps
is recommended if the installation allows.
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