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6.1.2 This clause specifies the scope and power supply capacity of important roads and locations that require dual power supplies.
6.1.3 In order to ensure that the lighting source works under normal voltage conditions, to ensure the service life and efficiency of the light source electrical appliances, the upper and lower limits of the supply voltage are specified. At the same time, a limit requirement is imposed on the allowable value of the deviation of the lamp terminal voltage under normal operating conditions, so as to avoid the situation where the voltage at the end of the line meets the requirements and the voltage at the beginning end exceeds the limit.
6.1.4 The design of street lamp power supply network must meet the requirements of urban road planning, and should also be installed in urban main trunk roads, prosperous neighborhoods, new high-rise buildings and new residential areas. The distribution line is gradually adopting underground cables or overhead insulated wires.
In the design of the street lamp power supply and distribution system, the correct selection of the power supply components and system structure can reduce the voltage deviation to a certain extent.
The three-phase distribution transformer of the D, yn11 junction group refers to a three-phase distribution transformer with a high-voltage winding as a triangle, a low-voltage winding as a star, and a neutral point and an "11" junction group, D, yn11 junction It is much smaller than the zero-sequence impedance of the Y, yn0 junction, which is beneficial to the removal of single-phase ground short-circuit faults. In addition, the Y, yn0 junction transformer requires that the neutral current does not exceed 25% of the rated current of the low-voltage winding, which severely limits the balance of single-phase loads such as the use of street lamps, which affects the full utilization of the capabilities of the transformer equipment. In low-voltage power grids with TN and TT system grounding, it is recommended to use D, yn11 junction group distribution transformers.
In addition, Article 7 of the recommendations of the China Electrotechnical Society's Industrial and Building Applications Committee in November 1986 on the design of anti-shock protection for low-voltage power grids states: “D,yn11 junction transformers should be used in TN systems†. Since the voltage levels at various points of the power grid are different, the voltage conversion ratio and voltage tapping of the transformer can be reasonably selected, and the voltage of the power supply and distribution system can be adjusted to a reasonable level. In addition, it is necessary to control the range of voltage deviation, usually using the following measures:
(1) The voltage loss of the power supply component is proportional to its impedance. Under the premise of technical and economical rationality, reducing the number of voltage transformation stages, increasing the line cross section, and using cable power supply, the voltage loss can be reduced, thereby narrowing the voltage deviation range.
(2) Reasonable compensation of reactive power can reduce the voltage deviation range.
(3) In the three-phase four-wire system, if the three-phase load distribution is uneven (phase-to-neutral line), a zero-sequence voltage will be generated to shift the zero point, one of the voltages of the phase is lowered, and the voltage of the other phase is increased. High, increasing the voltage deviation. Since China has not yet established a national standard for the asymmetry limit of three-phase voltage and current, this standard proposes to balance the three-phase load as much as possible.
6.1.5 In order to minimize the impact of circuit failure on lighting, single-phase protection is usually used in the design of power supply and distribution of street lamps. When an overload or short-circuit fault occurs, single-phase operation may occur. Since the light source of road illumination is mainly a gas discharge lamp, there is a certain harmonic current in the circuit. In order to ensure the operation safety, especially the cable line does not allow overload in principle, it should be considered according to the most unfavorable situation. In addition, the neutral line section and the phase line section are also equal to meet the pressure drop requirements and can reduce the line loss.
6.1.6 The purpose is to avoid large-area light-off caused by single-lamp failure and to minimize the scope of the fault. According to the requirements of the relevant electrical standards, it is not necessary to separately set the protection unless the protection circuit of the upper line has been able to protect the section or branch line with the reduced section, or the loop current is below 20A.
6.1.7 According to the definition of relevant regulations, isolated buildings (buildings) with a height of more than 15 m, civil and general industrial buildings with a height of 20 m or more higher than other buildings or at the edge of the building are classified as three types of defense. Ray construction, the general requirement for lightning protection against lightning strikes in such buildings is to install lightning protection belts or wall lightning rods in buildings susceptible to lightning strikes.
6.1.9 The TN-S grounding mode is to strictly separate the working neutral line N from the special protection line PE. The advantage of using it is that when the system is in normal operation, there is no current on the dedicated protection line, but there is an unbalanced current on the working zero line. . There is no voltage on the PE line to the ground, so the zero protection of the metal casing of the electrical equipment is connected to the special protection line PE, which is safe and reliable; the disadvantage is that if the PE line is disconnected, it will not be protected and may cause an electric shock accident.
The TT grounding form is to directly ground the metal casing of the electrical equipment, thus reducing the risk of electric shock. The advantage of using it is that it is safer. The disadvantage is that the fault current is small, and the instantaneous overcurrent release of the fuse or circuit breaker cannot be used. It also acts as a ground fault protection, and the residual current protector should be used for ground fault protection. At this time, the protection sensitivity is higher; however, due to factors such as outdoor humidity, if the line is too long, the leakage current is large. If the setting current is improper (the setting value is too small), it will cause malfunction, so it is required to correctly and properly set it. Operating current. In addition, the metal poles need to be grounded. When each pole is grounded, the distribution line does not need to be equipped with a protection line (PE).
The design should be based on the above characteristics of the system, combined with the specific conditions of the street lamp power supply system, choose to use TN-S system or TT system.
6.2 Lighting control
6.2.1 Urban road lighting control should be based on time control and supplemented by light control functions. First of all, according to the geographical location (latitude and longitude) and seasonal changes of the region, refer to the information provided by the National Observatory for the time of the morning light or the lighting management unit, and the corresponding relationship between the morning and evening time and the illumination in the year, to reasonably determine the opening of the street light. Turn off the light. In addition, consider the deviation from the average due to weather changes. For example, sometimes during the day, you may encounter thick clouds and heavy rains. In this case, you need to turn on the street lights to provide illumination. In this case, an auxiliary light control function is required to automatically turn on the street light, and when the weather returns to normal, the street light can be turned off in a timely manner. For those cities that are temporarily unable to implement time control and light control to cope with the need for temporary lighting, manual intervention of manual control should be appropriately enabled to make the road lighting on and off accurately and reasonably.
6.2.2 In view of the current “three remote†system of road lighting that is being actively promoted and applied in various places, in order to ensure that in the event of a communication line failure or when monitoring the center, it will not cause a large area to be extinguished for a long time, it should be configured in the control system. This feature ensures the normal operation of road lighting.
6.2.3 This regulation stipulates the illuminance level of the switch lamp. The illuminance level of the turn-on and turn-off lights specified in the original standard is 2~10lx. After several years of practice, and through the study of foreign experience, the illuminance level of the lamp will be turned on when the standard is revised. Increase to 15lx, turn off the light level to 30/20lx, for the following reasons:
(1) Increase the level of illumination when turning off the lights, that is, delay the time to turn off the lights. Before and after turning off the lights in the morning, the urban roads gradually entered the period of heavy traffic. If the lights were turned off when the natural light level was 2lx, the road illumination was immediately reduced from 20~30lx to 2lx. The human eye encountered dark adaptation problems and the driver was near. In 10 seconds, the vision decreased or even disappeared, which made this time a high-risk period for various traffic accidents. In recent years, many media reports and letters from the masses (including motor vehicle drivers) have reflected this problem and strongly urged the delay in turning off the lights. Therefore, improving the illuminance level of turning off the lights is a scientific and reasonable measure.
(2) Regarding the illumination of the lighting, it is set to 15lx, which takes into account:
1 When the light is turned on, the human eye encounters a clear adaptation, and the adaptation time is short, so the illumination of the light can be lower than that of the light off;
2 High-intensity gas discharge lamps have a delay effect, and 90% to 100% of the luminous flux can be achieved after 15 minutes of ignition, so it is not suitable to set the illumination of the lamp too low.
3 maintain a certain relationship between the illumination of the lights on and off.
(3) Refer to the relevant foreign standards for the opening and closing lamp illumination level. For example, the Australian standard recommends that the illumination level of the opening and closing lamps be 30 to 60 lx, and the German standard recommends that the illumination of the lamp be 70 lx. The illuminance ratio of the illumination level of the on and off lamps recommended by some countries is 1:2 to 1:3.
(4) Through actual measurement, on the basis of the current time of turning off the lights, postponed for 13 minutes or so, the illuminance can be raised from about 3lx to about 30lx, which means that the street lights need only ignite more than ten minutes every day, and the total number of lights increases every year. The power consumption is very limited, and these energy consumption can also be compensated by reducing the road surface brightness (illuminance) in the middle of the night. Increasing the illumination level of the lights on and off can effectively improve the quality of the road lighting environment and bring higher economic benefits.
(5) Different levels of road lighting have different illumination levels, so the illumination level when turning off the lights should also correspond to them in principle. However, in order to facilitate management and control, two illumination levels of 30lx and 20lx are specified. 
6.1.1 In view of the lack of resources for urban power supply lines, and from the perspective of resource sharing and improving the comprehensive benefits of resources, it is neither possible nor suitable to invest in the construction of 10kV street lamp power supply lines for cities that do not use 10kV dedicated lines. At the same time, the cities that used the 10kV street lamp power supply line in China basically switched to the 10kV city public network. However, in order to reduce the impact of peak-to-valley changes in urban public loads on the quality of streetlight power supply, this standard recommends powering the streetlight-specific transformers on the city's public network.