Design method for height and spacing of LED street light poles

　　The average illuminance of the road surface is one of the evaluation indexes of urban mor vehicle traffic road and pedestrian road lighting, and it is also an important reference index for street lamp configuration.  configure or replace an urban road with LED street lights, technically, it first involves the calculation of lighting related indicars. Using the "utilization coefficient" method  calculate is one of the relatively simple and effective methods.

　　The formula calculated by the "utilization coefficient" method absolutely imitates the conclusions of traditional lighting theory research. What we have  do is  input some experimental or theoretical data of LED street lights in formulas, get the results and compare them with the requirements of road lighting design standards. It goes without saying that these calculations are also necessary for the design, development, improvement, enhancement and marketing of LED street lights.

　　1. Concept

　　The utilization facr (U) is the ratio of the luminous flux directly illuminated on the road surface  the luminous flux emitted by all light sources, and is related  the height, elevation angle, arrangement method, and road width of the street lamp.

　　Luminous flux (Φ) is the sum of the energy emitted by the light source and received by human eyes. Indicates how much light energy is radiated per unit time, and the unit is lumens lm. Other representation methods: cd.sr (cd is the unit of luminous intensity: candela. Sr is the unit of solid angle steradian.

　　Illuminance (E) is the proportional coefficient between the luminous flux and the illuminated area, the unit is lux lx. 1lx refers  the energy that the luminous flux of 1lm is evenly distributed in an area of ??1 square meter, that is, lm/m2.

　　The average illuminance of the road surface (Eav) is the average value of the illuminance of each point measured or calculated at a predetermined point on the road surface in accordance with relevant regulations.

　　The maintenance facr (k) is the ratio of the average illuminance or average brightness of the lighting device on the specified surface after a certain period of use and the average illuminance or average brightness obtained on the same surface when the device is newly installed under the same conditions.

　　The installation height (H) of the luminaire is the vertical distance from the light center of the luminaire  the road surface.

　　The installation distance (S) of the luminaires is the distance between two adjacent luminaires measured along the centerline of the road.

　　Overhang length (XL) is the horizontal distance from the light center of the lamp  the adjacent side edge sne, that is, the horizontal distance of the lamp extending or retracting in the edge sne.

　　Effective pavement width (Weff) is the theoretical pavement width used for road lighting design. It is related  the actual width of the road, the overhang length of the lamps and the arrangement of the lamps.

　　2. Calculation formula

　　According  the definition of illuminance, E=Φ／A

　　(1) In the formula, A-irradiated area, m2

　　Average illuminance of road surface, Eav=F/(W*S)

　　(2) In the formula, F—the rated luminous flux of the street light source, lm;

　　W—road width, m.

　　S—installation distance, m;

　　Because street lights are installed at different heights, elevation angles, layout methods, road widths, etc., the utilization of the rated luminous flux of the light source is also different, so the rated luminous flux of the street light source must consider the "utilization facr" (U); this is one of them;

　　Second, because  maintain the average illuminance of the road surface, the light attenuation of the luminaire itself, the protection level of the luminaire and the wiping cycle must be considered, so the rated luminous flux of the street light source must consider the maintenance facr (k);

　　Third, because the street lights are arranged in a single row. Double rows are symmetrical, double rows are staggered, etc., which also affect the average illuminance, and the arrangement facr (N) must also be considered.

　　Therefore, formula (2), after considering the above facrs, is:

　　Eav=F*U*k*N／(W*S)

　　(3) This is the formula for calculating the average illuminance by the "utilization coefficient" method.

　　In actual engineering calculations, the average illuminance standard of the general road surface is required, that is  say, Eav is known. But more is  calculate the rated luminous flux F that meets the needs of the street lamp. The formula (3) is transformed in:

　　F=Eav*W*S／(U*k*N)

　　(4) Note that W in the formula should be the effective width of the road surface. See Table 3 for the calculation of the effective width of the road surface.

　　3. Relevant data

　　1. "Utilization facr" U

　　The "utilization facr" of LED street lights is shown in Table 1:

　　Note 1: W-road width, H-lighting installation height, called the lateral distance ratio.

　　Note 2: When there is overhang length, the tal "utilization coefficient" is "roadside utilization coefficient" plus "houseside utilization coefficient". (See "Journal of Illumination Engineering", September 1994, Vol. 5, No. 3, page 51).

　　Note 3: Data source: Xu Liancheng's "LED street lamp design and marketing strategy thinking based on market demand".

　　2. Maintenance facr k

　　The maintenance coefficient k specified by CJJ45 is shown in Table 2:

　　Note 1: Maintenance facr = light attenuation facr of light source * light attenuation facr of lamp pollution.

　　Note 2: Data based on the quality and environmental conditions of commonly used road lighting sources and lamps in my country, based on the premise that the lamps are wiped once a year.

　　3. Street lamp arrangement coefficient

　　There are generally four types of street lamp arrangement: single-sided, double-sided staggered, double-sided symmetrical, and road center. N=2 for symmetrical arrangement, N=1 for other arrangements.

　　4. Road width and effective width

　　The calculation of the effective road width specified by CJJ45 is shown in Table 3:

　　Note 1: Ws—the actual width of the road surface, in m; XL—the length of the overhang, in m.

　　5. Street lamp spacing

　　The relationship between street lamp spacing S, installation height H, and effective road width W specified by CJJ45 is shown in Table 4:

　　Note: Weff——effective width, m; curve section: radius below 1000m, spacing S is 50%-70% of the straight line.

　　6. The average illuminance requirements of the road surface

　　The standard values ??(maintenance values) of road lighting for mor vehicles specified by CJJ45 are shown in Table 5:

　　Note: The left side of "/" is the low-end value, and the right side is the high-end value. Please refer  the regulations of CJJ45 for details.

　　See CJJ45 for other types such as the standard value of lighting in the intersection area and the standard value of pedestrian road lighting.

　　4. Calculation example

　　It is known that the LED street lights are arranged on the main road, choose the low-grade value Eav=20lx, the actual road width Ws is 15m, the LED street lamp protection level is IP54, the street lamp spacing S is 30m, the street lamp installation height is about 12m, and the overhang length is 1.5m. Elevation angle 15°, symmetrical arrangement on both sides.

　　Determine k=0.65 from Table 2;

　　Calculate from Table 3 Weff=Ws-2*XL=15-2*1.5=12m;

　　Check from Table 4 that H=12m≥0.5Weff=6m; S=30m≤3H=36m meets the requirements;

　　From the foregoing, when the road lights are arranged symmetrically on both sides, N=2;

　　Check Table 1. The tal "utilization facr" of 15° elevation angle corresponding  W/H=12/12=1 is 0.72;

　　Bring in the formula (4)

　　F=Eav*Weff*S/(U*k*N)=(20*12*30)/(0.72*0.65*2)=7692(lm)

　　Choose a LED street light product with 7692 lumens or more  meet the illumination requirements.

　　Combine these materials and data in the office software EXCIE, select and enter various coefficients according  the actual situation  aumatically calculate the result.

　　Obviously, given the lumens of a certain LED street lamp, the average illuminance can also be calculated according  the conditions or setting conditions, and then compared with the requirem