Attention must be paid to electrical safety in city night lighting

Update:08 Oct 2021
Summary:

In recent years, some large and medium-sized cities in […]

In recent years, some large and medium-sized cities in my country have started night lighting projects in order to prosper the economy, develop tourism, improve the appearance of the city, and enhance the image of the city. Some have received good results and exerted good social and economic benefits. Environmental benefits. From a practical point of view, in the implementation of urban night scene lighting projects, social public safety is an issue that cannot be ignored and cannot be taken lightly. Night scene lighting is a public welfare undertaking that improves and creates the beautiful environment of the city at night, provides night life space for citizens to watch and activities, and enhances people's spiritual and cultural life taste; if safety is neglected, it will bring danger and threat to people, and cause personal injury. Or a catastrophic accident (such as a fire), which turns the original intention of benefiting the people into a bad thing that “causes harm to the people and harms the people”. Even this caused bad political influence. Therefore, in the construction and management of urban night scene lighting, safety matters are of great importance.

Night scene lighting may cause safety problems. Some high-altitude installations are struck by lightning, high-altitude winds cause people to fall from high altitudes, or buildings are damaged. Some light fixtures are not firmly installed and fixed or are severely corroded and fall off and hurt pedestrians. There are lights. Leakage of pole lamp holders may cause injury to pedestrians, serious traffic accidents (aviation, ship navigation, and vehicle driving) caused by light pollution and interference light, and neglect of safe operations in the construction of night scene engineering, which may cause casualties or cause major accidents (such as ten Many years ago, the fire in the Qunlin Market in the Jiefangbei area of ​​Chongqing was caused by the production and installation of advertising light boxes and electric welding, which caused flammable materials.)...and so on, we must attach great importance to it. Really regard the responsibility as more important than Mount Tai, and improve the night scene lighting. Safety awareness in all aspects of design, construction and management, strictly implement relevant technical regulations, strengthen quality supervision, strengthen legal concepts, clarify legal responsibilities, and leave no safety hazards.

The cause of a series of accidents is more about electrical safety. The policy of safe work is to give priority to prevention. The safety issues in city night scenes have begun to attract attention. In the “Night Scenery Standards” formulated and implemented in 2002, the last three chapters: power supply and distribution system, construction production and installation, and completion acceptance, all involve many safety-related issues. The provisions should be implemented conscientiously.

2 According to the negative characteristics of the night scene lighting power consumption, the night scene lighting power system is designed. Compared with other lighting power loads, the night scene lighting has low requirements for power supply reliability. Except for individual buildings with commemorative significance and significant political influence, and the venues for holding important events can be appropriately increased, they are generally classified as Class III electricity loads. However, the guarantee of power supply quality is indeed very necessary for the safe and reliable operation of night scene lighting, so there should be certain requirements for the quality of power supply. The guarantee of power supply quality is not only a unilateral affair of the power supplier, but also the power users (including the power used for night scene lighting) themselves have certain responsibilities.

The quality of power supply interacts and restricts the composition of the power supply system. Poorly designed power distribution system will make night scene lighting unable to operate stably and normally, faulty interruptions will occur from time to time, or interference will affect the entire power grid; poor power supply quality will not only affect lighting functions and lighting effects, but may also affect the safety of power supply , Become a hidden danger of accidents.

Since the night scene lighting electricity load is composed of single-phase 220V lighting appliances, and the overall capacity is not small, when designing the power supply and distribution system, the circuit should be divided reasonably, the three-phase load should be evenly distributed, and the phase balance should be achieved as much as possible. Very necessary (the electrical design code for civil buildings" stipulates that the capacity of the largest phase and the smallest phase in the three-phase power distribution system should not exceed because the various circuits of the night scene lighting are mostly single-phase loads, and sometimes it is difficult to achieve a three-phase balance under objective conditions. , It is easy to cause the neutral point shift; also because of the large non-linear load component in the night scene lighting system, the characteristics of the neutral line are somewhat special, so the transformer of the power supply system should be D, Ynll group, and the low-voltage grounding system should be TN *S or TN-C*S system.

The power load of night scene lighting is often wide and the line is long. Pay attention to the stability of the power supply voltage. Generally speaking, the power supply radius should not exceed 0.2km. If the voltage at the end of the electrical equipment is too low, the light source will not reach the normal light effect, or even Some gas discharge lamps cannot be started (ignited) to affect the landscape effect; measures must be taken to reduce the voltage drop (such as increasing the load surface of the conductor, etc.). The system voltage deviation value specified in the "Night Scenery Specification" is ±5%. It is +5%, -10%. In the night scene lighting, a large number of lamps using gas discharge light sources are used, and many lamps and lanterns accessories are inductive loads, and the natural power factor is mostly low (some only about 0.6), resulting in reactive power The load is large. Not only affects the power supply capacity of the power grid, but also heats up the distribution lines and affects the lifespan. Therefore, the "Night Scenery Specification" requires reactive power compensation (dispersed or concentrated) to increase the power factor to above 0.9.