Selection of fire emergency lighting power supply

With the continuous deepening and development of reform and opening up, all walks of life are changing with each passing day. The rise and change of the construction industry is even more rapid and diverse. Modern buildings are in various shapes and forms, and gradually show the characteristics of high, large, complete and new. The number of floors of modern buildings is getting higher and higher, the area is getting larger and larger, the internal facilities are getting more and more complete, the functions are getting more and more complete, and the equipment and materials used are getting newer and newer. The internal flow of horizontal and vertical traffic in a building is also getting larger and larger. We hope that these buildings (including underground parts) will have uninterrupted power supply, but in fact various disasters are also possible. Such as: fire, explosion and earthquake and other disasters. When these disasters occur, the normal power supply often fails or must be disconnected, and the normal lighting is all extinguished. In order to ensure the safety of personnel and property, and to operate and handle the ongoing production and work in a timely manner, and effectively stop the spread of disasters or accidents, emergency lighting should be put into use immediately.

1 Classification of emergency lighting

Emergency lighting is lighting for personnel evacuation, safety protection or continued work when the normal lighting system fails due to power failure.

Emergency lighting is different from ordinary lighting. It includes three types: backup lighting, evacuation lighting, and safety lighting.

1.1 Backup lighting

Emergency lighting is the part of the lighting system that is used to ensure that normal activities continue when the normal lighting power supply fails. Backup lighting should usually be installed in the following places:

(1) Places where failure to operate or handle the power failure in a timely manner may cause accidents such as explosions, fires, and poisoning, such as certain operating parts in hydrogen production, paint production, chemical industry, petroleum, plastics, celluloid and its products production, explosives production, and solvent production.

(2) Places where failure to operate or handle the power failure in a timely manner will cause chaos in the production process or damage to the precious parts being processed. Such as certain processes in the chemical and petroleum industries, steelmaking furnaces in metallurgy, aerospace and other industries, metal melting and casting, heat treatment, and certain departments of precision processing workshops.

(3) Places where the failure of lighting will cause a greater political impact or serious economic losses. Such as important communication centers, radio stations, television stations, power plants and central substations, control centers, national and international conference centers, important hotels, international terminals, transportation hubs, important power supply stations (heating, gas, oil) and water supply facilities, etc.

(4) Places where the failure of lighting will hinder the fire rescue work. Such as fire control rooms, emergency generator rooms, broadcasting rooms and distribution rooms, etc.

(5) Important underground buildings will be unable to work and operate due to the failure of lighting. Such as subway stations, underground hospitals, large and medium-sized underground shopping malls, underground hotels, underground restaurants, underground garages and underground entertainment venues, etc.

(6) Places where the failure of lighting will cause the theft of cash and valuables. Such as the valuables sales area, cashier counters and bank teller counters in large and medium-sized shopping malls.

1.2 Evacuation lighting

Emergency lighting is set up to enable personnel to easily and accurately find the exit of the building when the normal power supply fails. Evacuation lighting should usually be installed in the following places:

(1) Public buildings with a large and dense population. Such as auditoriums, conference rooms, theaters, cinemas, cultural palaces, stadiums, large exhibition halls, museums, art galleries, large and medium-sized shopping malls, large waiting halls, terminal buildings and large hospitals.

(2) Buildings such as large and medium-sized hotels and large restaurants.

(3) High-rise public buildings and super high-rise buildings.

(4) Underground buildings with a large number of people. Such as subway stations, underground hotels, underground shopping malls, underground entertainment venues, and buildings with large areas without natural lighting.

(5) Large industrial plants with large numbers of people that are particularly important.

1.3 Safety lighting

Emergency lighting is the part of the building that is used to ensure the safety of people in potential danger when the normal power supply fails. Safety lighting should usually be installed in the following places:

(1) When the normal lighting in an industrial plant goes out due to a power failure, areas that may cause serious dangers such as contusions and burns to people in the dark. Such as circular saws with exposed knives and no protective measures.

(2) When the normal lighting goes out due to a power failure, the rescue of critically ill patients cannot be carried out in time, delaying the emergency time and possibly endangering the patient's life. Such as operating rooms in hospitals, emergency rooms for critically ill patients, etc.

(3) When normal lighting is extinguished due to power failure, places where a large number of people gather and are unfamiliar with the environmental conditions, which may easily cause panic and may lead to personal injury or death, or places where people cannot communicate with the outside world, etc.

According to the concept of emergency lighting and the places where emergency lighting should be installed, we can easily find that emergency lighting must meet both the general requirements of lighting and the special requirements of emergency functions. It must provide lighting in an emergency state and ensure that it is installed in the building all year round in a safe and reliable state. In addition to choosing a suitable light source, it is also crucial to choose a safe, reliable, long-lasting and durable emergency lighting power supply.

2 Classification of emergency lighting power supplies

Emergency lighting power supply is when the normal power supply no longer provides the minimum brightness required for normal lighting, that is, when the voltage of the normal lighting power supply drops below 60% of the rated voltage, it switches to the emergency lighting power supply for power supply. Emergency lighting power supplies can be roughly divided into the following types:

(1) Feeder lines from the power grid that are effectively separated from the normal power supply.

(2) Diesel generator sets.

(3) Battery packs: divided into the following situations:

1. The lamp has its own battery, that is, a self-powered emergency lamp.

2. Centrally installed battery packs.

3. Centrally installed battery packs in different areas.

(4) Combination power supply: that is, a combination of any two or even three of the above power supplies.

3 Determination of conversion time

The conversion time is determined according to the actual project and relevant specifications.

(1) The conversion time of standby lighting should not be greater than 15s;

(2) The conversion time of evacuation lighting should not be greater than 15s;

(3) The conversion time of safety lighting should not be greater than 0.5s;

The determination of conversion time is mainly based on the necessary operation, processing and possible accidents and economic losses. Some places require a shorter conversion time, such as the cashier counter in the center of the shopping mall should not be greater than 1.5s; For production sites with serious dangers, it should be determined according to their actual production needs. For evacuation lighting and standby lighting, it is easy to achieve automatic conversion. Even if a diesel generator set is used as an emergency power supply, automatic start and automatic conversion can also be achieved. For safety lighting, because the conversion time is extremely short at 0.5s, diesel generator sets cannot be used as emergency power supplies, nor can fluorescent lamps be used as light sources. Instantaneous incandescent lamps must be used and must be automatically converted.

4 Determination of continuous lighting time

From the types of emergency lighting power supplies and the requirements for conversion time, it is not difficult to see that the continuous working time of emergency lighting is subject to certain conditions. It is usually stipulated that the continuous working time of evacuation lighting should not be less than 30 minutes, and it can be divided into 6 levels such as 30, 60, 90, 120, and 180 minutes according to different requirements. The continuous working time of backup lighting and safety lighting should be determined according to the specific requirements of the place of use. For emergency lighting systems connected to the power grid or generator sets, their continuous working time is easy to meet the requirements; for emergency lighting systems powered by batteries, their working time is limited by the size of the capacity. For places that require a longer continuous working time, it is not appropriate to use battery packs alone, and they should be considered for use with generator sets. In this case, the battery pack is used only as a transition for emergency lighting, so its continuous working time can be appropriately reduced. When selecting an emergency lighting power supply, the continuous working time should be determined according to the specific situation.

5 Determination of emergency lighting power supply

The selection of emergency lighting power supply should be determined based on a variety of factors such as the type of emergency lighting, conversion time, continuous working time, characteristics of various power supplies, and the objective needs and requirements of the actual project, so as to ensure safety, reliability, advanced technology, and economic rationality.

5.1 Power supply from the power grid that is separated from the normal feeder circuit

This power supply has the characteristics of short conversion time (conversion time is easy to meet the requirements of various situations), long continuous working time, and reliable operation. Therefore, this power supply is widely used. It is especially easy to obtain this power supply in large and medium-sized cities and large and medium-sized factories. For public buildings and factory buildings, due to production and work needs, when there is a grid backup power supply, it should be used as an emergency lighting power supply first. It is not economical to set up such a power supply specifically for emergency lighting. It should be comprehensively considered in combination with the actual local power and the actual project situation, and the emergency power supply and emergency lighting power supply of power equipment should be arranged in a coordinated manner. For the backup lighting and the backup lighting of the fire water pump room that need to continue to maintain production, the same backup power supply should be used as the production power equipment and fire pumps, which is generally obtained from the power grid.

5.2 Diesel generator power supply

For emergency generator sets, since it takes a long time for the motor to be put into operation, the units that are often in the backup state take about 15 seconds to start up when the power is off. Therefore, they can only be used as emergency lighting power supply for evacuation lighting and backup lighting, and cannot be used alone for safety lighting. It is not economical and unreasonable to set up generator sets specifically for emergency lighting. In high-rise buildings, generator sets are often required to meet fire protection requirements; in some industrial production plants or communication and transportation centers, they are often considered together with the needs of power equipment for production and operation.

5.3 Battery power supply

Battery power supply can be divided into three types: built-in battery, centralized battery pack, and centralized battery pack in partitions. The built-in battery in the lamp is the self-powered emergency lamp. This method has high power supply reliability, rapid conversion and convenient increase and decrease, no impact from line failure, and small impact from battery damage. The disadvantages are large investment, continuous lighting time is limited by capacity, and high requirements for operation management and maintenance. This method is suitable for buildings with a small number of emergency lighting lamps, relatively scattered installations, and small scale. The advantages of centralized or zoned battery power supply are high power supply reliability and rapid conversion. Compared with the self-contained battery method, it requires less investment and is more convenient to manage and maintain. The disadvantages are that a special room is required, the battery failure affects a large area, and when the power supply distance is long, the wire cross-section is large, which will increase the copper consumption, and the fire protection of the line must also be considered. This method is suitable for buildings with a large number of emergency lighting lamps, concentrated lamps, and large scale. Therefore, in important public buildings and important underground buildings, it is sometimes necessary to use other types of emergency lighting power supplies in combination, which is more economical and reasonable. However, when such a power supply already exists in buildings such as computer stations and the capacity can meet the requirements, this power supply can be used as the emergency lighting power supply in this place.

5.4 Combined power supply

That is, a power supply method composed of any two or more of the above power supplies.

Since the structures and reliability of the above power supplies are different, the requirements and application scope of the system are also different. Therefore, in practice, it is sometimes difficult to meet the requirements by selecting only one emergency lighting power supply, and it is also difficult to be safe, reliable, and economical. At this time, it is necessary to select two or more emergency lighting power supplies.

When the emergency lighting power supply is an independent power supply from the power grid, it is required to draw two independent power supplies from the outside to ensure that when one fails, the other continues to work. The emergency lighting power distribution system should be self-contained to ensure that in the event of a fire, the system can still supply power after cutting off the non-fire load. In this way, the power supply capacity and power supply time are not limited, and the conversion time is easy to meet the requirements. However, in major disasters, its power supply reliability may be destroyed. Therefore, it is not enough to use only this method as an emergency lighting power supply for large-scale high-rise buildings and some particularly important buildings. At this time, it is necessary to use generator sets or batteries as necessary supplements and reinforcements for emergency lighting power supply.

The advantage of the generator set power supply method is that the power supply capacity and power supply time are basically unlimited, but the disadvantage is that the conversion time is long, and it cannot be used for safety lighting and backup lighting in some places with high conversion time requirements. When it is needed in such places, emergency lighting lamps powered by battery groups should be used as transitional lighting. High-rise buildings and some particularly important large buildings should adopt this power supply method that combines generator sets and batteries as emergency lighting power supplies.

6 Conclusion

In actual construction projects, the selection of emergency lighting power supply should be based on the number of floors, size, complexity, number of people staying and moving in the building, production and use characteristics in the building, fire hazard level and importance of the building, as well as the setting of other emergency power supplies, etc., and comprehensive consideration and technical and economic analysis and comparison should be carried out to select the best emergency lighting power supply. The combined power supply method has the advantages of more than two power supplies, and the disadvantages of one can complement each other. Although the investment is large, it is still widely used in high-rise buildings and some particularly important large buildings due to its high reliability.