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For economic reasons, fluorescent tubes (with a diameter of the voltage peak is displaced into the lamps. Therefore, an ad-
26 mm or 16 mm) and electronic ballasts are used for light ditional surge arrester must be installed in close proximity to
strips in industrial, commercial and agricultural buildings. the light strip.

In high halls, light strips with an extremely narrow-beam illu- The risk of surges entering the light strips is considerably re-
mination are installed. In this case, the regular replacement of duced if the frequently used class I light strips (PE connection)
luminaires alone (about 16,000 lighting hours in case of 26 mm are installed. If light strips feature luminaires with double or
tubes, about 20,000 lighting hours in case of 16 mm tubes) reinforced insulation, the light strip cables are often routed in a
entails high costs since aerial lift devices are required and the metal rail and are thus largely protected due to shielded design
luminaires are usually replaced outside working hours. of the metal rail.

But what if individual electronic ballasts are destroyed by In practice, light strips are operated with alternating current
surges or an entire light strip fails? In this case, immediate ac- (230 V / 50 Hz) and three-phase current (3x 230/400 V / 50 Hz).
tion is required since the necessary minimum illumination is For both types of supply, the maximum number of luminaires
frequently no longer ensured which may lead to a decrease in to be connected depends on the cross-section of the series
work performance and accidents. connected cables. To be able to consider the inrush currents
The IEC 60364-4-44 (HD 60364-4-44) standard deals with the of the electronic ballasts for the fuses, the luminaire manu-
“protection against overvoltages of atmospheric origin or due facturer specifies the maximum number of the relevant lumi-
to switching”. Section 443.3.2.2 describes that surge protective naires depending on the rated currents of the overcurrent pro-
devices (type 2 or type 3 arresters) can be used for commercial tective devices. This means that only 13 T26/58 W twin-lamp
buildings. electronic ballasts may be connected to e.g. a 16 A circuit
The often long supply lines of the light strips are highly suscep- breaker with characteristic B although the operating current is
tible to surges. Even a type 2 surge arrester or type 1 combined 13 x 0.58 A = 7.54 A. Since luminaires do not cause overload,
arrester in the power distribution board cannot prevent that the line must only be protected against short-circuits. The volt-

Type Part No.

DFL M 255 924 396

Figure 9.25.1 Type 3 surge arrester installed in an office luminaire

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