Today, street light manufacturer TIANXIANG will explain to you the precautions for municipal street light design.
1. Is the main switch of the municipal street light 3P or 4P?
If it is an outdoor lamp, a leakage switch will be set to avoid the danger of leakage. At this time, a 4P switch should be used. If leakage is not considered, a 3P switch can be used as the main switch.
2. Different layout methods of municipal street lights
Single-side layout-suitable for relatively narrow roads, he requires the installation height of the lamp to be equal to or greater than the effective width of the road surface. The advantages are good induction and low cost.
Staggered layout-requires the installation height of the lamp to be no less than 0.7 times the effective width of the road surface.
Symmetrical layout-requires the installation height of the lamp to be no less than half of the effective width of the road surface.
3. Reasonable selection of street light installation height, cantilever length and elevation angle
Installation height (h)-the economic installation height is 10-15m. If the installation height is too low, the glare of the lamp will increase, and if it is too high, the glare will decrease, but the lighting utilization rate will decrease.
Cantilever length – should not exceed 1/4 of the installation height.
Impacts of too long cantilever:
A. Reduce the brightness (illuminance) of the sidewalk and curbstone on the side where the lamp is installed.
B. The mechanical strength requirements of the cantilever become higher, affecting the service life.
C. Affect the appearance, resulting in an uncoordinated ratio between the cantilever and the lamp pole.
D. The cost will increase.
4. Elevation angle – The elevation angle of the lamp should not exceed 15 degrees
The installation elevation angle of the lamp is to increase the lateral illumination range of the lamp to the road surface. Too much will cause increased glare, and the brightness of the slow lane and sidewalk will be reduced.
5. Reasonable power compensation selection of municipal street lights
The single-lamp decentralized compensation method is used to increase the power factor of various lamps to more than 0.9, thereby reducing the capacity of the dedicated transformer for street lights by more than 51%, and the line loss by about 75%, which has a significant energy-saving effect.
6. Street light control method
Based on the principle of practical energy saving, the practice of most cities today is followed, and the control method combining light control and clock control is designed according to the different requirements of illumination during different traffic periods. That is, after dark, during the period of heavy traffic, all municipal street lights are turned on to ensure the safe passage of pedestrians and vehicles; after midnight, as the traffic volume decreases, all street lights on one side are turned off by clock control, so as to achieve the most economical energy-saving effect while ensuring normal traffic.
7. Selection of lighting power distribution method
Single-phase power distribution can be used for landscape lighting and road lighting with short power supply distance and small calculated load, and the voltage drop and terminal short-circuit current value should be verified. The distribution cabinet adopts outdoor type, and the bottom edge is 0.3 meters above the floor and installed on the ground.
For long power supply distance and large calculated load, three-phase power distribution is adopted, and the three phases A, B, and C in the low-voltage circuit are connected to each group of street lights in turn to avoid three-phase imbalance. The distribution cabinet adopts outdoor type, and the bottom edge is 0.3 meters above the floor and installed on the ground.
The three-phase five-wire circuit of the lighting low-voltage line can effectively reduce the line voltage loss compared with the traditional single-phase circuit.
8. Size and laying requirements of the protective pipe diameter of street light cables
The total cross-sectional area of the wires in the protective pipe should not exceed 40% of the cross-sectional area of the pipe. The inner diameter of the pipe should not be less than 1.5 times the outer diameter of the cable.
When the cable is laid in the green belt of the sidewalk, the burial depth is 0.5 meters. At the crossing point, it is changed to a D50 steel pipe with a covering depth of 0.7 meters. If the above requirements cannot be met, a layer of c20 reinforced concrete is added on the top of the pipe.
9. Specific practices of the TT grounding system of street lights
Use a local TT system without PE line, and add a 300mA leakage protector to the outgoing circuit breaker circuit. All lamp poles and lamps must be firmly connected to the steel bars of the lamp pole foundation as a grounding device, grounding resistance
10. How to choose a transformer according to the calculated load in street light design
The capacity of the transformer is not a problem, the key is the power supply radius. In engineering, the power supply radius of the street light box transformer is usually about 700 (if you want to be accurate, you must calculate the voltage drop), so one transformer is enough for 1.5 kilometers, and it is recommended to use 3 street light box transformers for 4.225 kilometers. The capacity depends on the total power of the street lights supplied by the transformer, plus a 50% reserve (some main roads need advertising lighting or reserve electricity for intersection street lights).
If you want to know more about the industry, please contact street light manufacturer TIANXIANG for consultation.
Post time: Mar-20-2025