The national standard GB 51309-2018 "Technical Standard for Fire Emergency Lighting and evacuation indication system" (hereinafter referred to as "Technical Standard") puts forward new requirements for the implementation of fire emergency lighting and evacuation indication system. The national standard atlas 19D702-7 "Emergency Lighting Design and installation" (hereinafter referred to as "Emergency Lighting") explains and demonstrates the "Technical Standard". However, due to the fundamental difference between the "Technical Standard" and the traditional practice, there are still some problems; after the release of the national standard GB 51348-2019 "Electrical Design Standard for Civil buildings" (hereinafter referred to as "Civil Standard"), many designers have doubts about the relevant provisions of fire emergency lighting. In order to clarify some fuzzy practices, this paper intends to discuss several problems in the implementation of fire emergency lighting and evacuation indication system for peer reference, improper, but also hope colleagues to criticize and correct.
Design basis of Fire Emergency Lighting and evacuation indication system
Fire emergency lighting and evacuation indication system is a system that provides lighting and evacuation instructions for places where people evacuate and still need to work in the event of a fire. This system is a part of the electrical fire control system. Because of its importance, emergency lighting is provided in the building design code and the relevant special electrical design code. Sometimes there are even provisions that are not easy to implement or contradictory provisions between the codes. In civil and general industrial buildings, we have reached the following consensus: the setting and scope of fire emergency lighting system should be mainly based on GB 50016-2014 Building Fire Protection Design Code (2018 version, hereinafter referred to as "Building Code"), and how to set up should be mainly based on the special fire protection standard "Technical Standard". When the contents of the fire emergency lighting and evacuation indication system in the relevant building and electrical standards such as the Civil Standard are inconsistent with the Technical Standard and the Building Code, the Technical Standard and the Building Code shall prevail.
Power supply, Distribution and switching of Fire Emergency Lighting
Since the battery power supply is not emphasized in the traditional emergency lighting practice, emergency lighting is also included in the end switching category of the fire power supply in the Code. Therefore, the traditional emergency lighting distribution box is a dual-power switching box, and the branch circuit is distributed in phases. Some projects are equipped with batteries in this dual-power distribution box, as the EPS power box, some projects have batteries on the evacuation sign lights, while the evacuation lights directly use part of the general lighting, the practices are different, the system is chaotic, and there are no specific standards on how to do it, but it is also a convention, and there is not much response and opinions.
The Technical Standard puts forward clear requirements for the power supply and distribution of fire emergency lighting and evacuation indication system, especially the power supply of fire emergency lamps should be composed of main power supply and battery power supply, and the main power supply is municipal power supply. according to whether the fire emergency lighting system is a centralized control system or a non-centralized control system, the main power supply determines whether it is a fire power supply or an ordinary power supply. The Technical Standard stipulates the power supply and power conversion of lamps and lanterns:
a. When the lamp is supplied by a centralized power supply, the main power supply and the battery power supply of the lamp should be provided by the centralized power supply, and the main power supply and the battery power supply should be supplied by the same distribution circuit after the output conversion is realized within the centralized power supply.
b. When the lamp is powered by its own battery, the main power supply of the lamp should be distributed through the emergency lighting distribution box to supply power for the lamp. After the main power output of the emergency lighting distribution box is disconnected, the lamp should be automatically transferred to its own battery for power supply.
c. In the centrally controlled system, the centralized power supply centrally set up shall be supplied by the special emergency circuit of the fire protection power supply, and the decentralized centralized power supply shall be supplied by the fire power distribution box of the fire protection zone and the same fire prevention zone floor; the emergency lighting distribution box shall be supplied by the special emergency circuit of the fire power supply or the fire power distribution box of the floor in the same fire prevention zone.
d. In a non-centrally controlled system, the centralized power supply set up centrally shall be supplied by the normal lighting circuit, and the decentralized centralized power supply shall be supplied by the normal lighting distribution box of the same fire protection zone floor; the emergency lighting distribution box shall be supplied by the normal lighting distribution box of the fire zone and the same fire zone floor.
From this, it can be seen that the fire emergency lamps and lanterns already have the switching of municipal power and battery power, and it is no longer necessary to set up a dual power switching box of municipal power, which meets the requirements of switching at the end of the Code. In addition, the "Technical Standard" regards the emergency lighting distribution box as a proper term, which specifically refers to the power distribution products with their own power supply, which is completely different from the traditional emergency lighting distribution box.
The problem of city power start-up when fire emergency lighting is cut off
Article 13.4.6 of the mandatory provisions of the Civil Standard stipulates: "evacuation lighting shall be controlled manually and automatically in the fire control room." It is not allowed to turn on the evacuation lights directly by cutting off the fire power supply. " Some people understand that it is not allowed to cut off the city power and turn on the evacuation lights, which is in contradiction with the "technical standards". This article is suitable for the centralized control system of type A lamps and lanterns, but it can not be satisfied for type B lamps and non-centralized control systems. The "technical standard" is based on the starting point of personal safety in the case of fire, and the principle of using battery power supply as far as possible in the case of fire. Therefore, for the centralized control system, if it is a type A lamp, the fire municipal power supply can not be cut off; if it is a type B lamp, the power supply should be cut off in case of fire. For non-centrally controlled systems, the municipal power supply is an ordinary power supply, and the municipal power should be cut off to start the emergency lights in case of fire. From the literal meaning, it is not a direct contradiction to cut off the municipal ordinary power supply to start the emergency light and not to cut off the fire power supply.
According to the requirements of the "Technical Standard", it is very easy to understand and implement the power supply to the traditional non-centralized control double-head wall lamp with its own battery, which is in line with the reality. It is powered by ordinary power supply, and the power supply is cut off and turned on in case of fire. If according to the traditional practice, the emergency lighting must use the fire power supply, and the fire power supply can not be cut off in case of fire. When using the double head wall lamp, its power supply and lighting will be caught in a paradox, which can not be justified. Therefore, the following provisions are made in the "General Code for Electrical and Intelligent Building", which is currently in the stage of application and approval.
"4.5.5 the power supply and distribution design of evacuation lighting and evacuation sign lamps should comply with the following requirements:
1 the lamps and lanterns shall be powered by the main power supply and the battery power supply. The battery pack should be charged normally and the power supply time of the battery pack should be ensured to meet the requirements of safe evacuation in case of fire.
(2) for the centrally controlled system, the main power supply should be supplied by the fire power supply. "
At the same time, it is added in the description of the provision: "the main power supply of the non-centrally controlled system should be supplied by the normal power supply, and the normal power supply should be removed and powered by the battery in case of fire, which can ensure the safety of evacuation and fire rescue personnel." The clear and clear methods for centralized and non-centralized control systems are given, and it is also helpful to understand that fire emergency lamps can be started with normal power supply and cut off normal power supply. The "Technical Standard" has given clear requirements, which completely solves the self-contradictory practice of traditional double-headed wall lamps.
Battery powered continuous working time
The Technical Standard stipulates that after emergency start-up of the system, the continuous working time of the battery power supply shall meet the following requirements:
"1 Civil buildings with a height greater than 100 m should not be less than 1.5 h.
(2) Medical buildings, care facilities for the elderly, with a total construction area of more than 100000 m2The public buildings and the total floor area are more than 20 000 m2The underground and semi-underground buildings should not be less than 1.0 hours.
(3) other buildings should not be less than 0.5 h.
4 Urban traffic tunnels shall comply with the following provisions:
1) Class I and II tunnels should not be less than 1.5 hours, and the station house connected to the tunnel port should not be less than 2.0 hours.
2) the third and fourth tunnel roads should not be less than 1.0 h, and the station house connected to the tunnel port should not be less than 1.5 h.
5 in the places specified in paragraphs 1 to 4 of this article, when designed in accordance with Article 3.6.6 of this Standard, the continuous working hours shall respectively increase the continuous emergency lighting time specified in the design documents (that is, in a non-fire state, after the main power supply of the system is cut off. The centralized power supply or emergency lighting distribution box should interlock to control the emergency lighting of the non-continuous lighting, and the light source of the continuous lighting should be changed from the power saving lighting mode to the emergency lighting mode. The continuous emergency lighting time of lamps and lanterns should comply with the provisions of the design documents and should not exceed 0.5 h).
6 the battery pack of centralized power supply and lamps and lanterns shall ensure that the discharge time meets the continuous working time specified in paragraphs 1-5 of this article after reaching the service life cycle. "
Among them, paragraphs 5 and 6 are more detailed and more specific than those required by the Construction Code, which relate to the fact that the evacuation lights can be lit after the main power is cut off in a non-fire state, but the longest lighting time can not exceed 0.5 h. If the main power supply is not restored during this period, the system needs to turn off the evacuation lights to ensure that in the event of a fire at this time, the battery power supply time meets the requirements of the Building regulations, and the technical standard requires that the battery power supply time should meet the power supply time in the case of fire and non-fire, but the non-fire time is not specified between 0 ~ 0.5 h. Emergency Lighting recommends the duration of battery power supply in a non-fire state, as shown in Table 1.
Table 1 increases the emergency time of the main power outage in the non-fire state on the basis of meeting the "Building regulations".2It needs to be clear here: this is the system design requirement that the battery should meet, not the requirement of the initial capacity of the battery! The initial installed capacity of 90 min specified in GB 17945-2010 "Fire Emergency Lighting and evacuation indication system", the nominal residual capacity of the storage battery after reaching the service life cycle can basically meet the requirements of 45 min;. Most of the existing fire emergency lamps and lanterns with batteries in GB 17945-2010 can meet the requirements of the standard, except for civil buildings and densely populated places with a height greater than 100m, especially residential buildings. In the design description, the continuous power supply time of the battery can meet the design requirements, and the initial installation capacity of the battery should be determined according to the charge and discharge characteristics of the battery, and the product should comply with the provisions of GB 17945. The new national standard GB 17945 is expected to be approved and implemented soon.
Power supply range and capacity of centralized power supply or emergency lighting distribution box
When supplying power to the lamps of different floors along the vertical direction of the electrical shaft, the power supply range of each output loop of the emergency lighting distribution box should not exceed 8 floors in public buildings and 18 floors in residential buildings. The power supply range of each output loop of centralized power supply should not exceed 8 floors in public buildings and 18 floors in residential buildings. Each centralized power box or emergency lighting distribution box has 8 circuits, which can supply a wide range of power, even more than 18 floors of residential buildings. However, it should also be noted that the capacity of each centralized power box can not exceed 1 kW, and each circuit can not exceed 6 A, which limits the scope of power supply can not be too large, need to be considered comprehensively, can not be considered only from a limited condition. According to the restrictions on the number of output circuits and current in the Technical Standard, the actual maximum lamp capacity allowed for each equipment is shown in Table 2.
In the actual project design, it is often encountered that many designers place a centralized power box in each shaft, and the power of LED emergency lights is relatively small, and only 2 of the 8 loops of centralized power are used on each floor; what is more, without doing lamp power statistics, it is directly written as 1 kW or 0.5 kW, resulting in greater waste. In general, a centralized power box distributes power to the upper and lower layers along the shaft, which is neither shared by too many layers, nor suitable for each layer. It is appropriate to have a centralized power box on the 3rd or 4th floor. The actual capacity of each centralized power supply should be calculated and is generally no more than 0.5 kW.
Protection of ultra-low voltage lighting device
Starting from preventing personal electric shock during fire prevention and rescue, when installing fire emergency lamps and lanterns at and below 8m from the ground, "type A fire emergency lamps and lanterns" should be adopted, that is, fire emergency lamps and lanterns requiring that the rated working voltage of the main power supply and battery power supply is not greater than DC 36V. For the fire emergency lamps and lanterns installed more than 8 m from the ground, "B type fire emergency lamps and lanterns" can be used. "B type fire emergency lamps and lanterns" is the fire emergency lamps and lanterns whose rated working voltage is greater than AC 36 V or DC 36 V. And it is stipulated that all buildings with fire control rooms adopt centralized control system. Thus it can be seen that most construction sites will use low-voltage DC power supply, that is, ultra-low voltage (SELV) power supply as defined by the International Electrotechnical Commission. From the voltage level, the protection against personal electric shock has a safety guarantee, but the reliable and safe operation of the SELV system can make the fire emergency lighting system safe and reliable. As the system is closely related to fire protection, the reliability of the system itself should be paid more attention to.
According to the national standard GB / T 16895.30-2008 / IEC 60364-7-71515 "Electrical installations of buildings-part 7-715: requirements for special devices or places-extra-low voltage lighting devices", ultra-low voltage lines can also cause fire accidents under the condition of short circuit fault. In order to prevent electrical fire, GB / T 16895.30-2008 adopts "special protection appliance" for ultra-low voltage lighting circuit, and puts forward the following requirements for this "special protection appliance":
"- continuous monitoring of the load of lamps and lanterns
-- when a short circuit fault occurs or other faults that cause a power increase of more than 60 W, the power supply is automatically cut off within 0.3 s.
When the power supply circuit is working under the condition of reducing power (for example, when controlling the conduction angle or in the process of power adjustment or when the light bulb is damaged), if a fault occurs that causes the power to increase by more than 60 W, the power supply will be cut off automatically.
When the switch of the power supply circuit is closed, if a fault occurs that causes the power to increase by more than 60 W, the power supply will be cut off automatically.
-- Special protective appliances should be those that do not affect safety even if the components fail. "
At present, domestic and foreign manufacturers of low-voltage electrical appliances have not produced this kind of "special protection appliances". Type An emergency lighting distribution box or centralized power outlet circuit simply uses fuses or circuit breakers below 6A as overcurrent protection devices. can not meet the above requirements of special protection appliances. In order to meet the above special protection requirements, the centralized power supply adopts the "micro-short circuit protection" technology for the switching power supply of LED lamps and lanterns, that is, the real-time monitoring of the output line of each power supply of the switching power supply is carried out, and the "follow" protection is realized for each load. No matter which load's working current, the centralized power supply will automatically set the effective protection value according to the actual load current. Thus, when a single load anomaly or short circuit occurs, the power supply can be cut off quickly and effectively and a warning can be issued, and the fuse or circuit breaker at the output end is only used as backup protection, which basically meets the requirements of "special protection appliances". This kind of protection should attract the attention of production and testing units.
This article has been deleted, and the full text is published in the 8th issue of Architectural Electric in 2021. For more information, please see the magazine.
The copyright belongs to Architectural Electric.
