Surge Protection for LED Lighting Systems
Causes of Overvoltages and Their Effects on Lighting Systems
Overvoltages have a highly destructive effect on electronic devices, including LED lighting systems. They can lead to premature wear and tear of LED drivers and LED modules, and even to the total failure of the lighting system.
Due to their exposed locations, public lighting systems are highly vulnerable to harsh environmental conditions. They are exposed to both nearby and distant lightning strikes and power surges; therefore, in locations where operational continuity is critical, these systems must be protected against lightning strikes and overvoltages.
Of the causes of overvoltages listed in international protection standards, public lighting systems are most likely to be affected by:
Direct lightning strikes on distribution lines (conducted through the power lines)
Lightning strikes near a building or structure (induced overvoltages)
However, the risks posed by overvoltages should not be overlooked in building systems either. In industrial and sports facilities, lights are usually installed at very great heights. In the event of a failure, the required minimum illuminance cannot be achieved if the lights go out, which can lead to an increased risk of accidents. Replacing defective components incurs not only hardware costs but also high expenses associated with the use of lifting platforms and service personnel, as well as potentially costly downtime (e.g., in industrial production facilities).
To prevent potential hazards and damage—and thereby ensure the continued operation of the facilities—appropriate investments in lightning and surge protection must be considered. The use of suitable surge protective devices (SPDs) can extend the service life of lighting systems, improve public services, and significantly reduce overall operating and infrastructure costs.
The vulnerability of electronic lighting systems to overvoltages is widely recognized in the technical literature, and various international regulations and standards stipulate the need for appropriate lighting protection.
For example, IEC 60364-1 requires protection against lightning and overvoltages for people, livestock, and property. Furthermore, the need for protection against the effects of lightning strikes can be determined through a risk analysis in accordance with the lightning protection standard IEC 62305. The luminaire standard IEC 60598-1 Luminaires—Part 1: “General Requirements and Tests,” Section 4.32, states: “Surge protection devices must comply with IEC 61643-11.” A key factor in ensuring effective protection is that the protection level of the surge protection device must be below the surge immunity of the luminaires and the LED driver.
What are transient overvoltages, and how do we protect LED equipment from them?
Overvoltages in power supply systems can be triggered by various causes and lead to damage or failure of LED lighting systems. Lightning strikes and switching operations typically cause transient voltage spikes that can reach tens of thousands of volts but last only a few microseconds. Despite their short duration, their high energy content can cause serious problems for electronic devices connected to the power grid, as the voltage spikes are usually well above the impulse voltage withstand capabilities of the connected electrical equipment (LED lights). The consequences range from premature aging to complete destruction, leading to operational disruptions and costly repairs.
While a few years ago the surge voltage resistance of streetlights was approximately 2–4 kV, today it averages about 4–6 kV. Top-quality luminaires even offer surge voltage resistance of up to 10 kV.
However, as shown in Figure 1, this is often insufficient, especially since the surge voltage resistance of the lights is usually determined by the so-called passive surge protection provided by the LED driver.
Figure 1: Possible causes of overvoltages and their magnitudes, as well as the rated surge voltage according to EN 60664-1 / VDE 0110.
As mentioned earlier and shown in Figure 1, transient overvoltages in power supply systems can be triggered by various causes. For example, lightning strikes that hit a building’s distribution line or its lightning rod directly can induce electromagnetic fields that generate voltage spikes in nearby lighting systems. Long outdoor power distribution lines are highly susceptible to the direct effects of lightning strikes, as large currents are conducted from the lightning into the power lines. In this case, we refer to so-called lightning surges. Depending on the distance from the strike location, the ground and grounding conditions, and the intensity of the lightning, lightning surges can reach very high levels. Figure 2 illustrates, in a general sense, how the light points of a street lighting system are affected by the formation of a potential funnel during a nearby lightning strike.
Figure 2: Potential overvoltage stress on light sources in the event of a nearby lightning strike
However, even “weather-independent” phenomena can cause voltage spikes in adjacent lines, such as switching devices (contactors) in control panels or the shutdown of transformers, motors, and other inductive loads or high-power equipment (generators, welding machines) that feed energy into shared branch circuits connected to sensitive electronic equipment, placing a heavy load on them (see Figure 3)
Figure 3: Overvoltages caused by switching operations in the power grid. For example, fuse tripping, switching of inductive loads, ground faults and short circuits, magnetic ballasts in mixed power grids ...
In this case, we are referring to so-called switching surges, which are caused by “switching operations in the power grid” and can reach values of several thousand volts.
A typical example in lighting technology is the tripping of fuses or mixed circuits containing both LED and conventional discharge lamps with conventional ballasts, which generate ignition voltages of several thousand volts.
Electrostatic discharge (ESD) is a phenomenon that occurs particularly in Class II luminaires, where charge separation takes place (Figure 4), and as a result, a high static voltage can build up on the luminaire housing or the LED heat sink, which can then discharge uncontrollably within the luminaire, potentially damaging the LEDs or the LED driver. Luminaires operated completely isolated from ground potential are particularly affected. Examples include Class II luminaires mounted on fiberglass-reinforced plastic (FRP) and wooden poles, or those suspended by cables. Standard LED luminaires available on the market generally do not provide adequate protection against this phenomenon and should, if necessary, be equipped with appropriately designed protective devices to prevent secondary damage caused by ESD.
Figure 4: Left – electrostatic charging in an insulated enclosure (SK II);
Right – Preventing static electricity buildup by installing an MLPC2-230L-V/ESP
Mains faults can lead to what are known as temporary overvoltages. The loss of the neutral conductor – for example, due to damage – is the most common cause here. In the event of this fault, the rated voltage on the phases can rise to as high as 400 V due to mains asymmetries in the three-phase system (Figure 5). Protection against temporary overvoltages requires special consideration because, unlike transient overvoltages, they can last significantly longer and therefore cannot be handled by conventional surge protective devices. Citel offers special devices from the "VM" series for this purpose.
Figure 5: Temporary Overvoltages Caused by a Drop in the Neutral Conductor
But there are also problems with building and warehouse lighting – particularly in cases where power surges do not originate from external sources but arise daily from the facility’s own electrical system. In particular, there are known cases in the industrial sector where electrical equipment generates power surges that travel through the electrical wiring to the lighting system. The first sporadic failures of individual lights or LEDs are typical signs of this problem.
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Effective Protection Concept
In general, the most effective approach to protecting large lighting systems from surges is to cascade multiple protection stages. Each stage provides the necessary balance between discharge capacity and voltage protection level. In this way, a first stage (typically a Type 1 or Type 2 SPD) provides robust protection and diverts most of the energy from a surge, while a second stage (typically a Type 2 or Type 3 SPD) offers “local” protection. The peak voltage and peak current reaching the equipment always remain below the critical value. Every installation has its own specific characteristics—therefore, SPD solutions should be tailored accordingly and include appropriate lightning protection and grounding systems. Properly executed grounding connections are essential for the effective functioning of a lightning protection system. The grounding connections must ensure proper contact in accordance with industry standards for the construction of electrical installations. The connection resistance must be low, and the conductivity of the grounding material must allow for efficient dissipation of surge energy.
The following components are therefore relevant to an effective protection concept against transient overvoltages: A. Street lighting main distribution panel (control cabinet | main distribution) B. Pole fuse box inside the pole (UV / sub-distribution) & luminaire(s)
CASE 1.) Street and outdoor lighting:
Figure 6: Protection concept for street lighting: Type 1+2+3 combined SPDs in the control center; Type 2+3 surge protection devices at the light points (in the pole and/or luminaire head)
Street Lighting Main Distribution Panel:
High-quality Type 1+2+3 combined SPDs can be installed in the main distribution panel to protect the central power supply where there is a good protective ground connection. This protects the main distribution panel—and thus the entire street—from a total outage. Indirectly, the lights are also protected (relieved) because a large portion of the transient overvoltages from the power grid is centrally limited. Good equipotential bonding between the light fixtures and the main distribution panel maximizes the protective effect.
Streetlight locations:
IEC 61547 stipulates that all luminaires should be protected against surges of up to 1 kV in differential mode and 2 kV in common-mode (standard protection at the luminaire level). In addition, protection up to 10 kV is recommended. The protection of individual light points depends on the specific situation. In principle, it is possible to install a high-performance Type 2+3 surge protection device (SPD) in the pole junction box or in the luminaire itself. Typically, a single protection device is sufficient. Since pole heights generally do not exceed 15 m, a good level of protection can already be achieved by installing the device in the pole junction box. Many luminaire manufacturers offer their customers the option of protecting their luminaires with an integrated SPD. If this is not possible or desired—for example, due to space constraints or because the luminaires are already installed in the field—the SPD can always be installed in the pole protection box.
The most sensible solution, therefore, depends on the specific local conditions.
Therefore, the following points are relevant when developing a solution:
Lighting fixture protection class: I or II
Space availability in the lighting fixture or in the pole-mounted safety box
Accessibility for maintenance purposes
Retrofit or new installation
In particular, the ease of maintenance and the ability to retrofit existing systems are arguments in favor of installation in the pole-mounted junction box. The slightly higher level of protection and the lower installation effort are arguments in favor of installation in the luminaire.
For Class I luminaires, the lighting system operator always has the option of installing surge protective devices either inside the luminaire or in the pole-mounted fuse box, since a protective conductor is available throughout the system and electrical safety is guaranteed in all cases.
Figure 7: Surge protection installed in a Class I luminaire … – left: in the cable entry box; right: in the luminaire. Ensure that the PE connection is continuous.
For Class II luminaires, according to the luminaire standard IEC 60598-1, surge protection devices compliant with IEC 61643-11 must not compromise the protective insulation. Optimal surge protection against the metal housing or ground is therefore not possible in a Class II luminaire. Only protection between L and N (in so-called differential mode) is possible without restriction. With metal poles, therefore, there would be no effective protection in the event of an increase in ground potential due to nearby lightning strikes.
Figure 8: Left: Protection Class I surge protection in a Protection Class I pole (with PE) with a Protection Class II light fixture;
Right: Protection Class II surge protection when both the light fixture and the pole are designed to Protection Class II standards
Installation in the pole safety box is possible in accordance with the electrical safety requirements of IEC 60364-4-41 “Installation of Low-Voltage Systems — Part 4-41: Protective Measures — Protection Against Electric Shock,” provided that the pole itself is not classified as Protection Class II. In many lighting installations, the pole fuse box contains a protective conductor that allows the pole and a Class I surge protective device to be integrated into the protective equipotential bonding system. Electrical safety—particularly the trip conditions—is ensured by connecting the protective conductor and the fuse, which is usually present in the pole fuse box. If the impedance of the protective conductor is insufficient—as is the case, for example, with TT systems—RCDs must be installed to achieve the required tripping times in accordance with IEC 60364-4-41. By electrically connecting the luminaire to the metal pole, even Class II luminaires can be effectively protected against lightning surges.
It is important not to overlook the protection of lighting control systems. Lighting control systems—such as phase control, DALI, 1-10V, DMX, and others—must always be included in the protection strategy. These systems are typically even more sensitive than 230V~ systems and are generally not protected by the electronic ballast. In this case, we recommend combined surge protection solutions for 230 V and lighting control in a single device to protect the luminaire (see Figure 9).
Figure 9: Combined SPD for power supply and lighting control in a single device.
Left: DALI; Right: Control phase
CASE 2.) Building Systems:
In building services engineering (Figure 10), effective protection can be achieved by equipping the electrical installation with suitable lightning and surge protection devices. For example, Type 1+2+3 combined SPDs can be used in the building power supply to protect against lightning currents and power grid transients, while Type 2+3 SPDs can be installed in lighting sub-distribution panels and luminaire junction boxes to protect against field coupling and switching surges.
Figure 10: Protection of an industrial building
Power supply: Combined SPD, Types 1+2+3; Lighting UV: Types 2+3; Lighting circuit: at least Type 3, preferably Types 2+3
Practical Surge Protection
When selecting surge protection devices, special attention should be paid to the following points:
A good surge protection device (SPD) should be tested and certified in accordance with IEC 61643-11 and meet the requirements of VDE 0100-534. To achieve this, status indicators and disconnect devices, among other features, are integrated into the SPD. These allow maintenance personnel to easily perform a visual inspection to determine whether the SPD is still functional. Regular inspection is essential.
Since the SPD is usually installed in concealed, inaccessible locations—such as inside light fixtures—visual signaling alone is not ideal. An SPD that can also disconnect the light fixture from the circuit in the event of a fault offers a good and simple means of indirect signaling in such cases.
The size and mounting type of the SPD must meet the requirements of the installation location.
If moisture or dust is present, an SPD with a higher IP rating should be selected.
SPDs must be compatible with the protection class (SKI or SKII) of the luminaires.
The SPD must be rated for the exact nominal operating voltage of the system. An SPD rated for a higher operating voltage does not provide better protection.
Low protection level; ≤1500 V; lower is better
In addition to protection for the 230 V power supply, protection for the control system—such as DALI, the second (control) phase, 1–10 V, or DMX—should be taken into account. SPDs that combine AC and control circuits are ideal for these luminaires and generally provide better-tailored protection than two separate SPDs.
When installing SPDs, always follow these guidelines: Install SPDs in accordance with local electrical codes and the SPD manufacturer's instructions.
Active Surge Protection vs. Voltage Withstand:
A key advantage of active surge protection devices is that they operate regardless of the magnitude of the surge. An SPD functions like a voltage-controlled switch. If the surge voltage is lower than the SPD’s activation voltage, the device remains inactive. If, however, the surge voltage exceeds the SPD’s activation voltage, the SPD diverts the surge energy and prevents it from damaging the equipment. When selecting the appropriate surge protection, the maximum energy absorption capacity is of critical importance. Here, the impact of lightning on the equipment must be taken into account, as well as the maximum surge voltage the equipment must withstand. It is important to consider the type of surge protection, the installation situation, and the risk to the system or to people. If, on the other hand, the insulation strength or voltage withstand capacity of a luminaire without active surge protection is exceeded, a total or at least partial failure of the luminaire is generally to be expected. To test how well current luminaires are structurally protected against surges (passive surge protection) and what additional benefits active surge protection components provide, a field test was conducted on luminaires from various well-known manufacturers. First, the luminaires with their standard-equipped surge protection were subjected to 15 pulses of up to 10 kV/5 kA; subsequently, the same test was repeated with a surge protector connected upstream.
While in the tests without upstream surge protection the lights failed one after another—since the test pulses exceeded the lights’ pulse withstand voltage at a certain level—in the tests with an upstream surge protection device, not a single failure of the tested systems was recorded, even at a pulse voltage of 10 kV (Figure 11a). The simple explanation: Unlike “passive” surge protection, where the surge withstand voltage is set to a specific maximum voltage level through purely design-based measures, the active surge protection device limits the voltage to acceptable levels (Figure 11b) and safely dissipates the generated surge current.
Figure 11a) (1.2/50 µs) Pulse voltage
Figure 11b) Voltage Limitation and Discharge Current (8/20 µs) by the SPD
LED technology is establishing itself as the new standard in lighting. Advances in this technology are leading to increasingly efficient and reliable solutions. Practical, customized surge protection devices and protection concepts (Figures 6 and 10) safeguard sensitive electronics against harmful surges. The additional cost of an effective surge protection concept for a lighting system currently amounts to less than one percent of the total cost. Surge protection measures are therefore a simple and, in many cases, indispensable means for every facility operator to maintain the long-term service life and reliability of the lighting system and to avoid follow-up costs.
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Product Overview
Street lighting with Protection Class II luminaire heads mounted on Protection Class I poles, with or without a second control phase. Should the surge protection be located in the luminaire head or in the pole junction box? The possible applications are diverse, as is the range of suitable surge protection solutions.
To help our customers quickly and easily determine the right surge protection and narrow down their options, we have created the following selection guide.
MLPC Series
The products in the MLPC series are designed to protect single-phase-powered 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 devices. Various models make it possible to implement the best possible customer-oriented solution. The MLPC series effectively protects the LED system, even against high-energy surges; depending on the version, it also protects the dimming system (DALI – MLPCH-230L-V/DL, control phase – MLPC1-230L-V/2L). The diversity of the product line is complemented by additional combined variants for optimized energy management (MLPC-VGx-230L-x, MLPCHx-230L-x) as well as additional protection against static electricity—ESD (MLPC2-230L-x/ESP2) or temporary overvoltages—TOV/POP (MLPVM2-230L-5A). Thanks to its very compact design and a maximum discharge capacity of 10 kA per pole, the MLPC series offers an excellent price-performance ratio. Connections are made via screw terminals (MLPCx-230L-V) or spring-loaded terminals (MLPCx-230L-R). Users can choose between single-sided (MLPCx-230L-x/50) or opposite-side (MLPC1-230L-x) connection terminals. The housing mounting procedure is identical for all versions thanks to standardized mounting holes. This provides users with the necessary flexibility while maintaining simple installation.
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MLPM Series
The MLPM series is a cost-optimized standard product line designed to protect LED lighting. It effectively protects the LED system with a maximum discharge capacity of 12 kA per pole, even against high-energy surges. The devices meet the requirements of the IEC 61643-11 and VDE 0675 standards and are classified as Type 2+3. This is also confirmed by the existing KEMA and ENEC certificates. Models are available in protection classes I (MLPM1-230L-R) and II (MLPM2-230L-R). The visual fault indication on the device is mechanical in nature, allowing the protective components to be inspected at any time, even when no mains voltage is present. Furthermore, the surge protector does not consume any additional energy, as is the case with electronic fault indication via LED. In the event of a fault, the fault message is conveyed indirectly through the disconnection of the lighting circuit (the light is OFF). Connection is made exclusively via spring-loaded terminals. As with all MLPC versions, the MLPM series also features identical, standardized mounting holes, which provide the user with the necessary flexibility while maintaining simple installation.
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MLPX Series
The MLPX series devices are Type 2+3 surge protective devices designed to protect single-phase end devices, particularly for use in LED lighting systems with space constraints. The MLPX devices comply with IEC 61643-11 and VDE 0675 and are available in protection classes I and II. A very compact design, a discharge capacity (Imax) of 10 kA, and a short-circuit withstand capacity of 10,000 A are hallmarks of the MLPX series’ performance. Connection is made via double-insulated cables, and the fault signaling function allows the operational status to be monitored at all times. In addition, the MLPX series offers the option of load circuit disconnection in the event of a fault, ensuring that an indirect signal is generated even in the event of a load circuit failure. The devices are available with either IP 67 or IP 20 protection ratings.
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MLPCA Series
The MLPCA series was designed to protect Class 1 equipment powered by a single-phase (MLPCA1-230L) or two-phase (MLPCA1-230-2L) supply and is specifically intended for installation outside a cable junction box. In addition, there are 2-port variants (2-port MLPCA1-230L-DL and 2-port MLPCA1-230L-2L), which are primarily used in ground-powered bollard lights. The MLPCA series complies with the IEC 61643-11 and VDE 0675 standards and is classified as Type 2+3. Thanks to its very compact design and a maximum discharge capacity of 10 kA per pole, the MLPCA series offers excellent value for money. Connection is made via cables, with the connecting wires housed in a highly flexible and durable rubber-sheathed cable. The MLPCA SPDs provide protection against switching surges from the power grid as well as against earth-bound potential rises.
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Surge Protection for DIN Rail Mounting - DSLP / DLPM / DACN10 Series
The devices in the DSLP, DLPM, and DACN10 series are all compact Type 2+3 surge protection devices designed for DIN rail mounting. Due to their compact design, they are ideally suited for use in pole protection boxes. They comply with IEC 61643-11 and VDE 0675 and are available in protection classes I and II (does not apply to the DACN10 series). The devices feature discharge ratings of up to 15 kA Imax, a low protection level (Up ≤ 1.5 kV), and a short-circuit withstand capacity of 10 kA. Connections are made via screw terminals for conductors up to 2.5 mm² or via elevator terminals for conductors up to 10 mm² in the DACN10 series. Fault signaling allows the operational status to be monitored at any time. In the DLPM series, this is indicated mechanically, while in the DSLP and DACN10 series, it is indicated electronically via LEDs. All devices offer the option of load circuit disconnection in the event of a fault, so that an indirect signal is also provided via the failure of the load circuits.
