Surge protection for LED-lighting

Protection concepts

The following components are relevant in an effective protection concept against transient surges:

• Streetlighting main distribution board
  
• Mast fuse box in mast
  
• Luminaire
  

Streetlighting main distributor:

High quality combi arresters type 1+2+3 can be installed in the main distribution board to protect the central supply where there is a good protective earth connection. This protects the main distribution board and thus the entire street lighting system from a total failure. Indirectly, the luminaires are also protected by centrally limiting a large part of the transient overvoltages from the mains supply. A good potential equalisation between the light points and the main distribution board increases the protective effect.

Streetlighting light points:

The protection of the individual light points depends on the situation. In principle, it is possible to install a surge protection in the mast fuse box or in the luminaire. Usually one protection device is sufficient. As the mast heights usually do not exceed a height of 15m, a good level of protection can also be achieved by installation in the mast fuse box.

The most sensible solution depends on the local conditions. Thus the following points are relevant:

• Luminaire protection class I or II
• Space conditions in the luminaire or mast fuse box
• Accessibility for maintenance purposes
• Retrofitting or new installation

Especially the question of maintenance and the possibility of retrofitting existing systems speak in favour of an installation in the mast fuse box. The slightly better level of protection and the lower installation effort are more arguments in favour of installation in the luminaire.

With protection class I luminaires, the light point operator always has the option of installing surge protection devices in the luminaire or in the mast fuse box, as a protective conductor is available here and electrical safety is guaranteed in any case.

For protection class II luminaires, surge protection devices according to IEC61643-11 must not break the protective insulation. An optimum surge protection against the metal housing or ground is therefore not possible in a protection class II luminaire. Only protection between L and N is possible without restriction.

Not to forget the protection of the lighting control. The lighting control systems like a control phase, DALI, 1-10V, RS485, DMX...must be included in the protection concept. These are usually even more sensitive than the 230V~ systems and usually not protected by the ECG. Here, coordinated surge protection solutions for 230V and control in one device are recommended to protect the luminaire.

The installation in the mast fuse box is possible under consideration of the electrical safety according to IEC 60364-4-41 "Erection of low-voltage installations - Part 4-41: Protective measures - Protection against electric shock", if the mast itself is not part of protection class II. In many lighting installations there is a protective conductor in the mast fuse box, which makes it possible to integrate the mast and a surge protection device into the protective equipotential bonding. The electrical safety, especially the switch-off conditions, are ensured by the connection of the protective conductor and the mostly existing Fuse in the mast fuse box reached. If the impedance of the protective conductor is not good enough, e.g. in TT networks, it is necessary to install RCD switches to achieve the necessary switch-off times according to IEC 60364-4-41. Thanks to the conductive connection of the luminaire to the metal pole, luminaires of protection class II can also be effectively protected against surges.

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State of the art

Surge causes, experiences and protection concepts

The trend towards LED lighting in interior and exterior lighting is steadily increasing closed. In the meantime, many local authorities and network operators throughout Europe have experience with the relatively new technology. It seems that the Advantages, especially in terms of energy savings and intelligent lighting control, will ensure that the proportion of LED solutions in lighting technology will continue to rise steadily in the future. In street lighting this is already evident in many cities, but the trend is also gaining ground in industrial and building lighting. However, here too it is clear that there are light and dark sides.

For some years now, it has been apparent that overvoltages in particular are a serious This can be a problem for the sensitive electronics. First feedbacks from the field confirm this. The city of Esbjerg has become the largest Failure of over 400 street lights reported as a result of a lightning strike. This is particularly noteworthy as Denmark is one of the regions with the lowest lightning is in Europe.

Lightning strikes can occur depending on the distance of the impact site, the ground and grounding conditions and the flash intensity reach very high values. Picture 1 shows qualitatively the influence of the light points of a street lighting system through the Formation of a potential funnel during a lightning strike.

During switching operations in the network, voltage peaks of several thousand volts, which spread through the low-voltage network and generate other Load operating resources.

A typical example is the triggering of fuses or mixed Networks with LED and conventional discharge lamps with conventional ballasts, which provide several thousand volts of ignition voltage.

Electrostatic charges are a phenomenon that is particularly common in Protection class II Luminaires occur in which a charge separation occurs (Fig. 3) followed by a high voltage at the lamp housing or heat sink of the LED. This phenomenon is very important for every car driver who has been known to get an electric shock when he tries to grab his car ...to the man who got it.

Particularly affected are luminaires which are operated completely isolated from the earth potential will be. Examples are SK II luminaires on plastic masts or wire suspensions. By using the "MLPC2-230L-V/ESP" protective device these static charges and consequential damages are prevented.

Mains faults can lead to so-called temporary overvoltages. The Drop in the neutral conductor, e.g. due to damage, is the most common cause here. With this fault, the rated voltage can increase due to network unbalances in the 3-phase mains, increase the voltage up to 400 V on the phases (Fig. 4). The protection against temporary overvoltages requires special consideration. Citel offers here special devices of the PSPD and VM series.

But there are also problems in building and hall lighting. Especially where overvoltages do not come from outside, but daily from the own system. In particular, cases from industry are known in to which electrical equipment generates overvoltages and to which they are the electrical wiring to the lighting. First sporadic failures of individual luminaires or LEDs are the typical signs of this.

Also on the basis of this experience, luminaire manufacturers have developed their requirements to the strength of the luminaires against overvoltages. Storage a few years ago the resistance of street lights to overvoltages at approx. 2,000 - 4,000 V, it currently averages approx. 4,000 - 6,000 V.

However, this is often not enough, as can be seen from Picture 5

To take this into account, many luminaire manufacturers offer the option of Luminous due to a powerful type 2+3 surge protection device (SPD) to protect. If this is not possible or desired, e.g. due to lack of space or because the lights are already installed in the field, the SPD can also be installed in the mast fuse box can be used. This also offers the advantage of simpler Maintenance and retrofitting. To complete the protection concept and to relieve the light points (Fig. 6) should be additionally equipped with a combi arrester type 1+2+3 in the street switching/Central distributor against the propagation of lightning currents and overvoltages to be protected.

In building services engineering (Fig. 7) effective protection can be achieved by equipping the electrical installation with lightning and surge protection devices. For example, Type 1+2+3 combined lightning and surge arresters for protection against lightning currents and mains transients can be installed in the building supply system, and Type 1+2+3 combined lightning and surge arresters can be installed in the lighting systems. SPD type 2+3 sub-distribution boards and lamp junction boxes for protectionare used against field coupling and switching overvoltages.

Practical surge protection

There are many manufacturers for surge protection on the market. Therefore When selecting surge protection devices, the following points should be considered be given special attention.

1. A good surge protection should be tested according to IEC 61643-11 and requirements of VDE 0100-534. In order to achieve this, among other things status signalling and disconnecting devices are integrated in the SPD.
2. Since the SPD is usually concealed in inaccessible places, e.g. in luminaires is installed, pure optical signalling is not ideal. An SPD that can additionally disconnect the luminaire from the circuit in the event of a fault a good and simple possibility of indirect signalling.
3. The size and type of mounting of the SPD must meet the requirements of the installation site. correspond to this.
4. In case of moisture or dust, an SPD with an increased IP class should be selected.
5. SPDs must take into account the protection class (SKI or SKII) of the luminaires.
6. In addition to the protection for the 230 V supply, the protection of the control unit, such as DALI, second (control) phase, 1 - 10 V or DMX can be taken into account. SPDs that combine AC and control are ideal for these luminaires and usually offer better coordinated protection than two individual SPDs.

Field test on different lights

In order to test how well current luminaires are constructively protected against overvoltages and what additional benefits active overvoltage protection components provide, luminaires from the market leader WE-EF and other manufacturers were tested. First of all the WE-EF luminaires with the standard surge protection installed were loaded with 15 pulses of up to 10kV/5kA according to the test sequence shown in diagram 1.

During the tests with surge protection devices, none of the tested systems failed to operate with 10kV (Fig. 1) pulse voltage. The integrated surge protection device limits the voltage to acceptable values (Figure 2) and the pulse current is safely reduced by the surge protection device.

Conclusion

LED technology is becoming increasingly important in lighting. The further development of technology ensures ever more reliable solutions. Practice-oriented, adapted Surge protection devices and protection concepts (Figures 6 and 7) Fuse the sensitive electronics from harmful overvoltages. The additional Costs of an effective surge protection concept for a lighting system are currently less than one percent of total costs. Overvoltage protection measures are therefore an important factor for every system operator. simple and in many cases indispensable means to ensure the long-term durability of the and reliability of the lighting and to avoid follow-up costs.

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Product overview

Street lighting with protection class II luminaire head on a protection class I pole, with or without second control phase. The surge protection in the luminaire head or in the pole connection box? The possible applications are many and varied, as is the choice of suitable surge protection solutions.

In order to quickly and easily determine the appropriate surge protection and to narrow down the selection, we have prepared the following selection guide for our customers.

MLPC series

The products of the MLPC series have been designed for the protection of 1-phase supplied end devices for protection classes 1 (MLPC1) or 2 (MLPC2). The devices meet the requirements of the IEC 61643-11 and VDE 0675 standards and can be used as type 2+3. Due to the very compact design and a max. discharge capacity of 10 kA per pole, the MLPC series offers a very good performance ratio. The connection is made via screw terminals (MLPC1-230L-V) or spring terminals (MLPC1-230L-R). The user can choose between one-sided (MLPC1-230L-x/50) or opposite (MLPC1-230L-x) connection terminals. The mounting of the housings is identical for all versions due to standardized mounting holes. This offers the user the necessary flexibility while maintaining the same ease of installation.

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MLP Series

The MLP Series is a comprehensive range of LED lighting protection products. Different variants enable the best possible customer-oriented solution to be implemented. The MLP series effectively protects the LED system, even against high-energy overvoltages, including dimming (RS485 or DALI) depending on the version. There is a choice of versions in protection classes I and II as well as various options for error signalling and disconnection in the event of an error. Depending on requirements, the lighting circuit can be disconnected from the lighting circuit or only the overvoltage protection can be disconnected from the mains. The fault signal is given optically, via a potential-free contact or indirectly via the circuit separation of the lighting circuit.

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MLPX series

The MLPX series is a type 2+3 surge protection device designed to protect single phase supplied terminals, especially for use in LED lighting systems with space constraints. The MLPX are IEC 61643-11 and VDE 0675 compliant and available in protection classes I and II. A very compact design, a discharge capacity (Imax) of 10 kA and a short-circuit resistance of 10000 A are characteristic for the performance of the MLPX series. The connection is made via double-insulated cables and the error signaling allows the functional capability to be displayed at any time. In addition, the MLPX offers the possibility of load circuit separation in the event of a fault, so that an indirect message is also given about the failure of the load circuits. The devices are optionally available in protection classes IP 67 or IP 20.

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DSLP series

The devices of the DSLP series are type 2+3 surge protection devices for top hat rail mounting. The DSLP are IEC 61643-11 and VDE 0675 compliant and available in protection classes I and II. The devices have discharge values of 10 kA Imax, a low protection level and a short circuit resistance of 10 kA. The connection is made via screw cages up to 2.5mm². The functional capability can be read at any time via the error signaling. The DSLP offers the possibility of load circuit separation in the event of a fault, so that an indirect signal is also given about the failure of the load circuits.

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MLPCA series

The MLPCA series has been designed to protect 1-phase (MLPCA1-230L) or 2-phase (MLPCA1-230-2L) powered terminal devices for protection class 1 and is specially designed for installation outside a junction box. The MLPCA series complies with the IEC 61643-11 and VDE 0675 standards and can be used as type 2+3. Due to the very compact design and a max. discharge capacity of 10 kA per pole, the MLPCA series offers a very good performance ratio. The connection is made by cable, whereby the connecting leads are located in a highly flexible and resistant rubber hose line. The MLPCA arresters offer protection against switching overvoltages from the mains as well as against earth-bound potential rises.

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Surge protection for LED-lighting systems

Technical contribution

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