Table of Contents
LED lighting fixtures have made considerable strides in recent years and provide significant potential for energy savings. LED luminaires can provide excellent lighting performance at a lower cost in a variety of lighting settings or traffic environments thanks to continuously improving efficiency, optimized luminaire design, and flexible lighting management.
Although LEDs are being utilized more and more in outdoor lighting, their benefits and corresponding standards are still not widely understood, which keeps them from gaining a significant share of the market. The recommendations in this article, which are primarily directed at municipal decision-makers and procurement specialists who are in charge of commissioning new or upgraded street lighting installations, concentrate on the design and procurement of street lighting systems. The standards could also be beneficial to producers of lighting, project contractors, energy consultants, and designers and planners of street lighting.
The reader’s unique situation and goals will heavily influence the advice in this article. For instance, professionals who are already aware with the fundamentals of LED street lighting (Luminance, Glare, CCT, CRI, IP, IK, IEC protection, SPD, Efficiency, Lifetime, Warranty, Price) can skip ahead to chapter 5 to explore recommendations for specific procurement criteria. For beginners, experts should start with chapter 2. The fundamentals of comprehending procurement standards are covered in this chapter, including the EN 13201 standard and the main quality and efficiency factors of city street lighting.
The measurements listed below are used to measure how much light is produced by a lighting system and how much is seen by the human eye. They consist of brightness, luminous flux, luminous intensity, and illuminance.
Luminance as per EN13201
The entire amount of radiation emitted by a specific light source that is visible to the human eye is known as luminance flux (measured in lumens, or lm). The luminous flux used in photometry is a measurement of the perceived power of various lights since the human eye responds differently to various wavelengths (for instance, green light is more sensitive than red or blue light). It differs from radiant flux, which is modified to reflect the various wavelengths of light to which the human eye is sensitive.
The entire amount of light that reaches a specific lighted surface area is known as illumination (measured in lux, or lx, where 1 lux = 1 lm/m²). For various road categories, the EN13201 standard provides minimum illumination standards. Normal conditions would dictate that both motor vehicle lanes and non-motor vehicle lanes (such as sidewalks) have brightness standards. The typical illumination needs of footways and bicycle lanes range from 2 to 15 lux. EN 13201 provides recommendations for standard illuminance and illuminance requirements.
The expression of the spatial distribution of light, or the luminous flux inside a certain solid angle from the source, is the luminance intensity (in candela or cd, where 1 cd = 1 lm/radian square). Any upward lighting is frequently unwanted in street lighting, where spatial distribution must assure adequate lighting for roads, street furniture, and road users.
Brightness comes next after introducing the luminous intensity. The brightness of an illuminated surface or item as seen by the human eye is represented by luminance (measured in cd/m²). When light goes in a specific direction, brightness is a photometric measurement of the luminous intensity per unit area. It speaks of the quantity of light falling within a specific solid angle. For motor vehicle lanes, the recommended minimum brightness ranges from 0.3 to 2cd/m². If you’re interested, you might review the EN13201 standards, which outline the minimum brightness criteria for road categories encompassing various highways.
A glaring visual effect is one that requires the eye to quickly adjust and is brought on by an unnatural brightness distribution or excessive contrast. Two common glare effects are
- Disable glare, which reduces contrast sensitivity as a result of light scattering inside the eye,
- Uncomfortable glare that causes people to feel uncomfortable.
Different classifications for discomfort and incapacitating glare are introduced, classifying various levels of shielding. Shielding levels for discomfort glare range from D1 to D6, whereas shielding levels for disability glare range from G1 to G6. When examining the IES of LED light, the disabling glare can be obtained by using the table. I A-0.5, in unit cd/m, is the discomfort glare index, where:
With a 0,5 m diameter and an intensity of 60 cd per 1000 lm of bare lamp output, a light sphere is visible from any angle. The apparent area is equal to 0.5 x 0.5 / 4 m² = 0.20 m², and the glare index value is equal to 134 for each 1000 lm light output at 60 x 0.20 x 0.5. Using 50 W LED street lights for this specific luminaire results in classes D5 according to current lamp output values.
High brightness levels from LED light sources can produce glare. To lessen this brightness, diffusers are typically included with LED lights. The brightness of the lit area and the light source shouldn’t differ significantly from one other in street lighting systems. Additionally, eyestrain can be brought on by often shifting illumination levels, thus this should be avoided, especially on lengthy drives. The TI value is typically the major topic when simulating city street lighting.
Luminous intensity classes
|Class||Maximum luminous intensity in directions below the horizontal of the output flux of the luminaire.||Other requirements|
|at 70° and aboveb||at 80° and aboveb||at 90° and aboveb|
|G*4||500||100||10||Luminous intensities above 95° b to be zero|
|G*5||350||100||10||Luminous intensities above 95° b to be zero|
|G*6||350||100||0c||Luminous intensities above 90° b to be zero|
- Luminous intensities are given for any direction forming the specified angle from the downward vertical with the luminaire installed for use.
- Any direction forming the specified angle from the downward vertical, with the luminaire installed for use.
- Luminous intensities up to 1 cd/klm can be regarded as being zero.
Despite frequently emitting light with a wide variety of distinct wavelengths, light sources are only thought to have one hue. The correlated color temperature is the name given to this light source’s hue. The temperature of the Planck radiator closest to the color of the light source is called Correlated Color Temperature (CCT), and it is determined by heating the Planck radiator to a specified temperature (measured in Kelvin). Warm light is around 2700K, neutral white is around 4000K, and cool white is at 5000K or greater; CCT is specified in degrees Kelvin. Regional preferences in Europe for both interior and outdoor lighting colors vary. For instance, “cool white” (blue) lighting is more common in southern European nations while warm white lighting is preferred in central and northern European nations. As a result, citizens of Central and Nordic nations could find high color temperature light to be less pleasant.
When compared to prior lighting technologies, LED lighting provides the flexibility to change or choose the color temperature for a variety of purposes. However, it should be remembered that the color temperature of the light source affects the lighting system’s energy efficiency, which could have physiological consequences on both people and animals. For the lighting system, cool white light with a high color temperature offers a higher level of energy efficiency. On the other hand, there may be safety and health concerns due to the strong blue light present in cold white light sources, which must be taken into account. White light, which supports the human eye’s perception more effectively than yellow light, appears brighter, according to research. Consequently, white light (e.g., 4000 K) is typically preferable in complex traffic circumstances involving several types of road users (e.g., vehicles, bikes, and pedestrians). Lower, warmer color temperatures, on the other hand, might be more appropriate for spaces with larger dimensions.
Along with correlated color temperature, the term “chromaticity,” which refers to a color’s precise coordinates in the spectrum, can be used to describe the color uniformity of a specific kind of lamp. A MacAdam ellipse is a graph that illustrates variations in light color over time or throughout a batch of lights. The dimensions of the MacAdam ellipse can be used to illustrate the color consistency of a specific lamp or luminaire type. There are often 3 steps, 5 steps, and 7 steps. The color consistency of 3-step LEDs is higher than that of 5- or 7-step LEDs. Currently, a 5-step McAdam ellipse is the minimum required, while some projects call for 3-step LEDs.
Color coordinates and MacAdam ellipses can be used to specify and assess color variation over time. Since aging LED modules can alter their color temperature and color coordinates, color maintenance is especially important for LED lighting. Material deterioration, contamination, or other sorts of system deterioration used for the LED package or lens might lead to problems with color maintenance. Greater working temperatures, higher operating currents, and optical material degradation brought on by blue or UV radiation could all be the direct causes.
Colour rendering index
A light source’s CRI rating compares it to natural or normal light sources in terms of how accurately it can display the color of diverse objects. Color representation of lighted areas and objects can vary substantially amongst light sources with the same color temperature. As a result, the color temperature and color rendering capability of the light source are not concepts; instead, they depend on the spectral wavelength that the light source emits, not the color temperature. A light source that offers the entire gamut of wavelengths can accurately depict all color nuances of lighted things. Only certain hues can be represented by light sources that emit only those colors.
Under controlled laboratory circumstances, a light source’s capacity to render eight specific standard colors is measured. The color rendering index describes how colors are rendered (CRI, with a maximum index of 100). For accurate facial recognition, a lighting setup with a color rendering of 80 or higher is recommended. LED bulbs typically have a color rendering index of 80 or better. In most cases, the Ra>70 color rendering is enough for streets with straightforward traffic patterns. Ra > 80 is preferred for usage and lighting scenarios that are more complicated.
Artificial lighting, such as light pollution or unauthorized outdoor light transmission, can be detrimental to both people and animals. The affects on people include excessive nighttime lighting in and around cities, as well as sleep disruption brought on by badly placed external lighting in residential areas. Animals, on the other hand, rely on natural light sources for navigation, therefore artificial illumination may mislead or scare them away. This has an impact on animal physiology, reproduction, and navigation. According to studies, LED street light sources repel insects better than other lighting technologies. “Warm white” LEDs (3000 K color temperature) repel insects substantially less than “cool white” LEDs (6000 K color temperature).
A light source that illuminates the area being lit. The use of LEDs in combination with directional light sources is very effective for achieving an optimal light distribution. In general, it is undesirable for light to emit above the light source.
The Upward Light Output Ratio, often known as ULOR or RULO, is a measurement of the amount of light that a luminaire emits upwards.
Total Lamp Lumen Output / Lamp Up Output.
Now BUG Rating has taken the place of ULOR. The Forward light, Back light, and Up light lumen ratios of LED bulbs are used to calculate the BUG rating. These are the lights that are above, behind, and in front of the LED light. These solid angles, which make up a portion of the whole 4 solid angle around the luminaire, are further subdivided into 10 secondary solid angles. We may get BUG ratings by estimating the lumen content of these secondary solid angles. The different lights and their qualities are visually shown in the image below.
To ensure their continuing normal operation, street lighting fixtures must be shielded from other substances (solid and liquid), mechanical trauma, and voltage fluctuations. Ingress protection, surge protection, and voltage protection requirements are typically specified for this reason.
According to the EN60529 directive of the European Committee for Standardization of Electronics, the enclosure’s IP grade is the level of environmental protection it offers. IEC 60529 is the comparable European standard. Additionally, it is listed in the EN/IEC 60598-1 general standard for LED lamps and lanterns. Typically, IP ratings contain two digits:
- First digit. The luminaire is shielded from solid objects or materials by solid particle protection.
- Second digit. Lamps are shielded from the impacts of liquids such as water, steam, etc.
For LED lighting fixtures, IP certification is highly significant. The general public will need IP66 test results for LED street lamps because they are utilized outside, including on highways, parking lots, squares, etc., and must have enough resistance ability to dust, particles, and bad weather.
|1st Digit||Protection against foreign/solid objects||2nd Digit||Protection against liquids and moisture|
|0||Not potected||0||Not potected|
|1||Protected against objects greater than 50 mm||1||Protected against vertical falling drops of water|
|2||Protected against objects greater than 12 mm||2||Protected against sprays of water up to 15 degrees from the vertical|
|3||Protected against objects greater than 2.5 mm||3||Protected against sprays of water up to 60 degrees from the vertical|
|4||Protected against objects greater than 1.0 mm||4||Protected against water sprayed from all directions|
|5||Dust is not entirely excluded, but cannot enter in sufficient quantity to interfere with the satisfactory operation of the equipment (dust proof)||5||Protected against low pressure jets of water from all directions|
|6||Totally protected against dust (dust tight)||6||Protected against high pressure jets of water from all directions|
|7||Protected against the effects of immersion between 15 cm and 1 m|
|8||Protected against up to 10 m of submersion|
|9K||Protected against close-range high pressure, high temperature spray downs|
International standards describe the IK rating or “impact protection” (K stands for “kinetic energy” to distinguish it from IP rating) as the degree of resistance an electrical enclosure offers to mechanical shock. The IEC 62262 standard specifies the IK code for luminaires’ mechanical impact resistance. EN/IEC 60068-2-75 and EN/IEC 60598 also discuss related standards. LED street lights with IK ratings between IK00 and IK10 are impact-resistant up to 20 joules. We advise that outdoor luminaires be at least IK08. This is because they could be directly destroyed or struck by falling branches or other debris in high winds.
Electrical safety (IEC)
Electrical protection makes ensuring that, in the case of a failure, components have enough insulation. An international institution known as the IEC (International Electrotechnical Commission) creates safety standards for the electrical industry. It has developed pertinent standards. Class I and Class II, which refer to the internal design and electrical insulation of lamps or power sources, are terms we are more familiar with. These regulations were created by IEC to safeguard consumers against electric shock. The prerequisites for Class I and Class II standards are as follows:
- Products in the CLASS I category additionally provide grounding treatment in addition to basic insulation for electric shock protection.
- Class II refers to a product’s anti-electric shock insulation structure or insulation type that does not only rely on basic insulation but also includes additional safety measures (double insulation) to prevent the occurrence of contact with faulty live parts. Class II is derived from the IEC standard or an equivalent standard.
LED power supplies, LED modules, and controls can sustain damage from transient overvoltages, which are voltages that last for a brief period of time and are greater than the usual design voltages. The overvoltage protection rating serves as a gauge of their resilience to this variation.
Although EN 61547 stipulates 0.5 kV (neutral to ground) as the minimal norm for overvoltage protection of LED lights, this is plainly insufficient for more severe circumstances like lightning strikes. Due to the development of a matching standard for surge protection devices in EN61643, many street light projects now refer to this standard when determining whether overvoltage protection must be at least 10 KV.
Since LED outdoor lamps are intended for outdoor use, the project party will need them to be able to withstand extreme weather. Because it resists corrosion, LED street lights are more useful in hostile locations like docks and beaches. How then can we increase the corrosion resistance of LED streetlights? We must first comprehend the principle of corrosion. Metals and alloys undergo an electrochemical process called corrosion in which they are converted into significant oxides, hydroxides, and water salts. Consequently, an electrochemical reaction takes place when lights (often aluminum alloys), salt, and water are combined. The use of barrier coatings (both electrophoresis and spray) to keep metal parts from being exposed to salt spray is one of the simplest and most affordable techniques to prevent corrosion. In general, LED lights treated in accordance with the necessary procedures have good anti-corrosion properties and can pass the salt spray test required by ISO9007/ASTM B117 and other pertinent standards.
Compared to most other technologies, LEDs offer exceptionally high levels of energy efficiency (lumens per watt of power). Currently, LED lighting technology may save 40% to 60% more energy than conventional lighting. When combined with an intelligent control system, energy savings can exceed 75%. Generally speaking, the more energy-efficient a lamp is, the less power it needs to illuminate a road and the higher its efficiency. The spatial light distribution (luminous intensity), the state of the roads, and the geometric configuration of the luminaire, however, all have an impact on a luminaire’s lighting effectiveness. High-efficiency lighting could occasionally need more watts than low-efficiency lamps. The Power Density Index (PDI) was created as an appropriate indicator to assess energy efficiency at the level of the road system. The Annual Energy Consumption Indicator (AECI), in turn, can more accurately depict the entire energy efficiency and consumption over the course of a year. Additionally, the project party (tenderer) and the manufacturer need to pay attention to these points.
The lengthy lifespan of LED lights is a significant benefit. The adoption of LED lamps over the last few decades provides more evidence that they are superior to conventional lamps in this area. Complex elements, such as electrical and thermal operational data, ambient temperature, and other parameters, affect the lifespan of LED bulbs. In general, the lumen maintenance time of the LED and the lumen maintenance time when LEDs are applied to the LED lamps will be used to calculate the service life. The LM-80, ISTMT, and TM21 reports are utilized to estimate the life, and the life is typically computed using the L70 result. The MTBF data of the power supply and the LxxByy report of the LEDs are also utilized as the foundation for calculating the lamp’s service life. LED bulbs typically have a lifespan of more than 50000 hours.
Smart control system
Smart Control is a dynamic street light management system that allows for the most real-time street light control possible. On the one hand, it can manage the switching and dimming of lamps by controlling them individually or in groups. However, the central control server can also gather data regarding the condition of the bulbs (for example, parameters such as faults, energy consumption, temperature, voltage and current). The programming of the luminaires can also be modified concurrently as needed for better and more effective project management. Most of these only involve alterations to the fixture’s internal software or real-time control, not to the hardware itself.
Mandatory requirements of award criteria of city street lighting project
Luminance and glare
The EN13201 standard specifies exactly what is needed for various types of roadways in terms of illumination. The M1 to M6 standards are typically used for motor vehicle lanes. It determines which brightness standard should be used for various driving scenarios (speed, traffic volume, traffic composition, separation of carriageways, junction density, parked vehicles, ambient luminance, etc). The most widely used standards for sidewalks and non-motorized vehicle lanes are P1 through P6, which primarily specify the illumination needs of the ground in accordance with the design speed, use intensity, traffic composition, parked vehicles, ambient brightness, and facial recognition. Yibai LED Lighting thinks that lighting requirements for planners and road users should come first for road developments. To demonstrate that the lamps offered are compatible with the project’s road conditions, the bidder must submit an appropriate lighting simulation and IES of the lamps. However, many projects merely specify the wattage and light output of bulbs at the moment, which we believe is inadequate.
Disability glare and discomport glare, which correspond to two levels including G class and D class, were clearly explained in EN13201. EN13201 also specifies the TI value for illumination simulation. In Yibai illumination simulation, the TI value must adhere to the required standard. Conditionally necessary items can only be of the G class or D class. Its G class and D class will differ as a result of varied bulb wattage, light distribution curve, installation angle, and lamp structure.
CCT and CRI
Standards are typically applied to projects involving street lighting. Yibai LED Lighting thinks that most vendors can easily accomplish these two goals, and all we need to do is make sure the project’s specifications are met. There are two things to consider:
- For CCT, we want to concentrate on how each region/country prefers CCT. As was noted in the preceding chapter, “warm white light” is preferred in central and northern Europe, whereas “cool white light” is more common in several nations in southern Europe, South America, and Africa. It is important to note that a growing number of projects are now requesting warm white light (below 3000K), since research to support this claim indicates that it has a less negative physiological effect on people and plants.
- For CRI, Yibai feels that CRI70 is enough for simulating street illumination, but CRI80 can be increased if the road circumstances are extremely intricate so that drivers can better assess the conditions, including obstructions, pedestrian traffic, and facial recognition for better response.
IK and IP
In order to ensure that the lamps can adapt to normal road conditions and usual weather conditions, municipal street lighting should meet the most fundamental protection requirements of IP65 and IK08. The IP rating can be raised to IP66 or higher in extremely harsh weather conditions (such wind and sand). IK09 or IK10 may be needed for outdoor stadium lighting due to the luminaire’s protection from hits from balls in motion.
Electricity is inherently harmful, and electrical equipment is inherently risky. Electrical protection guarantees that components have appropriate insulation in the event of a failure to avoid an unacceptable risk of bodily injury. Therefore, some projects need two layers of insulation to provide protection and keep users away from problematic live parts. Given the prevalence of Class II protection, Yibai advises using Class II standard lamps and lanterns when appropriate.
Transient voltages must be prevented from harming facilities, equipment, or terminal equipment by using surge protection. Thus, the primary functions of the surge arrester are to restrict the amplitude of the surge voltage and ensure that the device’s dielectric strength is not exceeded. Limits the surge discharge currents brought on by surge voltages. The system should typically have a surge of 10KV surge protection, which can shield the majority of lamp overvoltages. In order to make sure that the lights are better able to resist damage from surges, Yibai thinks that it should take into account upgrading to a 20KV surge protection device if there is a lot of lightning in the area where the lamps are located.
We do not believe that lamps’ surfaces require special treatment for general projects because they typically undergo a surface treatment procedure and are subjected to adverse weather conditions, such as acid rain and a small amount of salt spray environment. Yibai thinks that specific treatment, such as electrophoretic phosphating and electrostatic spraying of particular coatings, is necessary for the surface of lamps when your project is near the sea (indoor lamps such as food factories). This can guarantee the lamp’s structural integrity in inclement weather, safeguard the regular operation of the electronic components inside the lamp, and thus enable the lamp to operate better when used for street lighting projects.
LED post top lights and street lights can reduce electricity use by more than 40% when compared to conventional LED lighting. LED is a good option for preserving the planet’s deteriorating ecological situation. The main justification is that LEDs have a higher luminous efficiency than conventional lights, but how can we make our LED street lights more energy-efficient? We must first consider the luminous efficacy of bulbs. In general, bid projects will award higher points to lamps with excellent luminous efficiency. Yibai thinks it is appropriate to emphasize light efficiency while also paying attention to lamp wattage. The reason is that, despite some lamps’ high light efficacy, they may not always produce a suitable lighting impression due to their illogical light distribution (lens). The two models of street illumination, for instance, employ 20W lamps. The lamps in the simulation on the right produce 140lm/w of light. Despite the left image’s 130lm/w light effect, it is clear that the lighting effect is superior. In this instance, the lamps in the photo on the right must raise their wattage in order to achieve the effect of the one on the left, making them less competitive.
The lifespan of LED bulbs is intended to range from 50,000 hours to 100,000 hours or even more (calculated by L70). In comparison to the majority of high pressure sodium lamps, metal halide lamps, or high intensity discharge (conventional street lamps) light sources, it often has a longer life (about 3-6 times). Like all other light sources, LED light sources gradually lose their ability to convert electrical energy into light energy, but it is possible to slow this down with the right expertise. We mostly consists of these three things:
- The lamps’ heat dissipation
- The LEDs’ driving current
- The LEDs’ build quality.
These three factors have a bigger effect on the LED’s lifespan. Additionally, the MTBF-based measurement of the LED power supply’s quality is crucial. It is advised to use L70 and MTBF as Award points since extended lifetime indicates that the luminaire can service your project for a longer period of time.
Under the terms of the warranty, the seller may decide, in its sole discretion, to repair, replace, or refund the purchase price of the LED light if it is found to be defective. Municipal street lighting installations have a longer project cycle. If the project side offers a warranty, that indicates the owner will have a guarantee. To ensure that the lamps can serve the project for a long time and protect the rights and interests of the owners and users, most projects now offer 5–10 years of product quality assurance. A product with a long warranty period, according to Yibai LED Lighting, demonstrates the manufacturer’s trust in the quality of the product and has a naturally high rating.
The cost of the lamps’ maintenance, power usage, and installation are all included in the price. Yibai thinks that the cheaper a price is, the less desirable it is. It will always be true that “you get what you pay for,” thus we should make every effort to select street lamps with great cost-performance. The luminous efficacy, lifespan, and warranty are the primary factors that need to be taken into account for high cost performance. Of course, the cost of the light itself and how challenging maintenance is must also be taken into account. It is essential to carefully analyze the street lamp options that are best for your project. You can get in touch with us or read our post on “How much do the street lights cost” if you’re curious about the cost of an LED street light.
We hope that by reading this post, everyone will have a better grasp of what luminance, glare, CCT, CRI, IP, IK, IEC protection, SPD, efficiency, lifetime, warranty, and price of street lights represent and how important these elements are when making decisions about street light projects. Of fact, LED bulbs have many more features than just these. The architecture of the luminaire, the power source’s use of LEDs, and certification are all crucial elements. We simply wanted to write this essay to let everyone (project parties, buyers, and suppliers) know that there are a lot of issues we need to address. Finally, we think there is still a lot of promise for the LED sector. We hope that this article will draw the attention of all concerned parties and offer guidance for the creation of pertinent standards and pertinent guidelines for LED lighting systems. You are welcome to write to Yibai LED Lighting if you have different views or are interested in different street lights so that we can communicate and advance together.