Ten knowledge points for street lamp pole design
Advantages and disadvantages of different layouts of street lamp pole design.
One-sided arrangement – for narrower roads, he requires that the installation height of the lamp be equal to or greater than the effective width of the road surface.
The advantages are good inducibility and low manufacturing cost.
The disadvantage is that the brightness (illuminance) of the road on the side where the lamp is not set is lower than the team on which the light is placed.
Staggered layout – requires the installation height of the lamp is not less than 0.7 times the effective width of the road surface.
The disadvantage is that the longitudinal uniformity of the luminance is weak, and the inducibility is not as good as the unilateral arrangement.
street lamp pole design installation height, reasonable selection of cantilever length and elevation angle
Installation height (h)—The economic installation height of the gas discharge lamp is 10-15m.
The installation height is too low, the glare of the lamp increases, the high glare decreases, but the lighting utilisation rate decreases.
Cantilever length – should not exceed 1/4 of the mounting height. Impact of long cantilever:
1. Reduce the brightness (illuminance) of sidewalks and curbs on the side where the lamp is installed.
2. The mechanical strength of the cantilever becomes higher and affects the service life.
3. Affect the appearance, resulting in the inconsistent ratio between the cantilever and the light pole. 4. The cost will increase.
Elevation angle – The elevation of the lamp should not exceed 15 degrees.
The installation elevation angle of the luminaire pole is to increase the illumination range of the luminaire on the road surface.
Excessive conventions cause excessive glare, and the brightness of slow lanes and sidewalks is reduced.
Street lamp reasonable power compensation selection
The single street lamp pole design dispersion compensation method is used to increase the power factor of various lamps to more than 0.9.
Which can reduce the capacity of the transformers for street lamps by more than 51%?
And the line loss can be reduced by about 75%, which has a significant energy saving effect.
The choice of lighting distribution methods
For single-phase, power distribution for landscape lighting and road lighting with short power supply distance and small calculation load.
The voltage drop and terminal short-circuit current value shall be verified.
The power distribution cabinet adopts outdoor type, and the bottom side is installed 0.3 meters above the ground floor.
For long power supply distances and large calculation load, three-phase power distribution is adopted.
The three phases of A, B, and C in the low-voltage loop are connected to each group of street lamps in turn to avoid unbalanced three-phase.
The power distribution cabinet adopts outdoor type, and the bottom side is installed 0.3 meters above the ground floor.
The use of three-phase five-wire loops in low-voltage lighting circuits can effectively reduce line voltage losses compared to traditional single-phase loops.
Street lamp cable protection pipe size and laying requirements
The total cross-sectional area of the protective conductor shall not exceed 40% of the cross-sectional area of the pipe.
The inner diameter of the tube should not be less than 1.5 times the outer diameter of the cable.
The cable pipe was buried in the green belt of the sidewalk with a depth of 0.5 meters.
And the steel pipe at the street was replaced with a D50 steel pipe with a thickness of 0.7 meters.
If it can not meet the above requirements, then add a layer of the c20 reinforced solid layer on the top of the pipe.
Street lamp TT grounding system specific practices
Using a local TT system that does not have a PE wire, a 300 mA leakage protector is added to the outlet circuit breaker circuit.
All poles and lamps must be firmly connected with the low steel bars of the poles. Grounding devices should be used.
Grounding resistance should be less than 30Ω. After the base construction of the poles is completed.
The grounding resistance must be tested to meet the requirements.
If the conditions are not met, the grounding level must be increased. , see the specific practices: “National Atlas of Architectural Design,” grounding device installation 03D501-4.
How to design a street lamp according to the calculation load
The size of the transformer is not a problem. The key is the problem of the power supply radius.
In engineering, the power supply radius of the street light box is usually around 700 (if it is necessary to calculate the pressure drop accurately).
Therefore, a transformer of 1.5 kilometres is used, and 4.225 kilometres is recommended. 3 street light boxes changed.
See if the total power of the transformer for the circuit lamp is determined by the capacity, plus 50% of the reserve (some trunk roads need to be advertised or reserve cross street lamps)
First, your power calculation has missing items, the NG250 of the lamp is the power of the high-pressure sodium light source, do not forget the power of the ballast, generally 10-20% of the power of the light source, this is the estimated value.
If the lamp is selected There is a ballast’s power value, which can be added directly.
Second, you are more worried about the transformer capacity.
Therefore, if the power (KW unit, powerful energy) is added together, if it does not exceed 80 kW, this total can be directly divided by 0.85 (that is, the street lamp power factor), and the resulting number is assumed to be S1. Let the transformer splits S1.
The capacity meets the requirement at 70-85%. Or use S1 divided by 0.8 to see the value, select the transformer closer to the standard ability.
Of course, street lamp pole design should consider traffic signal power, advertising power, and public landscape power.
The transformer capacity is usually set at 70%, but it must be combined with the owner to reserve the power.
If the transformer capacity is more significant than 100KVA, we must consider the low voltage compensation.
The calculation method of the above method, but the power factor of 0.85 is changed to 0.9 or 0.92