Analysis and discussion on common problems in electrical design of high-rise residential buildings?

The electrical design of high-rise residence includes the following contents: power supply and distribution system, lighting, lightning protection and grounding, fire alarm system, telephone and network system, cable TV system and building intercom system.

The focus of the construction drawing review is to check whether the design of the above-mentioned electrical system conforms to the mandatory provisions, corresponding provisions, safety and energy-saving regulations in the current national or industrial norms.

2 key issues and analysis

The problems existing in the electrical design of high-rise residential buildings mainly focus on the general description of construction drawing design; Strong and weak electricity distribution system; Power supply and lighting plane; Lightning protection and grounding plane, etc.

2. 1 General description and legend of the design

Problems: invalid version specification is quoted, load classification is wrong, pipeline selection is improper, fire prevention measures are not taken for laying fire lines, fire prevention and sealing and sound insulation measures are not taken when pipelines pass through walls and floors, energy-saving articles are incomplete, safety sockets are not used in the legend table, emergency lights and evacuation signs do not indicate standby power supply type and continuous power supply time, and various energy-saving lamps do not indicate ballast model.

Analysis:

1) Common invalid codes are: Code for Lightning Protection Design of Buildings (GB 50057-94), Code for Residential Design (GB 50096- 1999), Code for Design of Low Voltage Distribution (GB 50054-95) and so on. It should be changed to the current version numbers of GB 50057-20 10, GB 50096-201and GB 50054-201,and should be JGJ 242-201.

2) The exposed cables, power supply trunk lines of fire control facilities and emergency lighting of public evacuation passages in high-rise residential buildings shall be selected according to the provisions of JGJ 242-2016.4.3, 6.4.4 and 6.4.5. At the same time, it should be clear that the distribution lines of fire-fighting electrical equipment should be installed openly and concealed.

3) The energy-saving design of high-rise residential buildings includes: efficient light sources and lamps should be used for public area lighting; Energy-saving measures should be taken for elevators, pumps, fans and other equipment used in houses (see clauses 10. 1.4 and 10. 1.5 in GB 50368-2005). Specially remind designers that high-rise residential projects with boiler rooms and heating stations in the basement should be equipped with power meters, water pumps and lighting meters respectively.

4) One of the common mistakes in the legend table: the sockets installed by households with a height of 1.8m or less shall be safety sockets, and the word "and" shall not be omitted, that is, 1.8m shall be included. Personally, the author thinks that in view of the numerous manufacturers of indoor switch sockets in China, the safety level of products is generally low, and all sockets used in houses should be safe.

The types of emergency lights in the legend table include emergency ceiling lights, emergency wall lights, evacuation sign lights, emergency ceiling lights in power distribution room (electricity meter room), emergency lights in fire fan room and fire water pump room. The types of standby power supply used are divided into centralized emergency power supply device (EPS) and lamps' own batteries. In the legend table, it should be clear which of the above methods is used for emergency light standby power supply, and the continuous power supply time should be marked.

Residential building lighting lamps can be divided into indoor lamps and outdoor lamps according to different installation positions, and outdoor lamps generally refer to public * * * area lamps. In the design drawings, the wiring of lamps in the family can be reserved to the position of lamp interface, and the specific lamps and light sources cannot be selected, so it is recommended to use energy-saving lamps when selecting lamps; Clear requirements should be made for the selection of lighting fixtures in public areas from model to light source.

2.2 Power supply and distribution system

Problems: the power distribution scheme is unreasonable, the main incoming switch of power supply is not selected correctly, and the incoming switch of household distribution box is not selected correctly.

Analysis:

1) The unreasonable distribution scheme is manifested in the following aspects:

(1) The power supply is not set separately for the metering equipment needed by the power industry and the metering equipment needed by the property. For the convenience of metering, it should be set separately from the power supply.

(2) There are too many vertical trunk circuits of distribution, resulting in unnecessary investment waste. It is suggested that one vertical trunk line be used for one staircase and two households below 18 floor, and two vertical trunk lines be used above 18 floor.

(3) Household meter boxes are not installed on every floor, but on every three or more floors, which seems to save the number and investment of meter boxes, but it is not. One of the problems brought by this design is that the meter box is large, occupying a large area of tube wells and increasing the pool area; The floor electrical shaft without meter box is very empty and wasteful. The second problem is that it is inconvenient for residents to check their meters and swipe their cards, so they can't check the remaining power in time. Therefore, it is best to set meter boxes on each floor of high-rise residential buildings. 1/3 123 Last page

2) Single-phase incoming line should be adopted for each floor of the household meter box, and if three-phase incoming line is adopted, the load of each floor can not reach three-phase balance. It is recommended to use single-phase cable for each meter box, which is also convenient for maintenance and safe use of electricity.

3) The main switch of residential power supply incoming line adopts ordinary circuit breakers, or only the leakage fire monitoring system is added, which can't meet the requirements of article 8.5.2 of GB 50368-2005, article 8.7.2 of GB 50096-201and article JGJ 242-201kloc. The main incoming line of residential power supply should be equipped with a residual current action protection device or an independent fire residual current action alarm, which should be able to cut off the power supply in time and give an alarm in case of grounding fault to avoid causing electrical fire.

The incoming switch of household distribution box should be a switching appliance that can disconnect the phase line and the zero line at the same time, which is convenient for management while ensuring safety.

2.3 Power and Lighting Plan

Problems: Water blocking measures have not been implemented in the main incoming lines of electric power and weak current, fire prevention measures have not been taken in the metal tank, emergency lights and evacuation signs are not set correctly, and the calculated illuminance value and power density value do not conform to the relevant provisions of the code.

Analysis:

1) High-rise residential buildings are generally equipped with basements. When introducing strong and weak electric pipelines through external walls, water should be stopped to prevent outdoor water from entering the basement through cable holes. In recent years, some high-rise residential basements have been flooded by rain, one of the reasons is that the cable entrance is not blocked.

2) There are many underground pipelines in high-rise residential buildings (especially the underground garage is connected with the underground storage room), and the metal bridge of the distribution line of fire fighting equipment is not marked with any fire prevention measures except the overall dimensions, which does not meet the provisions of Article 9. 1.4 (strong text) of GB 50045-95. The closed metal trunking box shall be marked on the outer side of the metal bridge, and fire prevention measures shall be taken, such as painting fire retardant paint on the outer side and adding partitions on the inner side.

3) Emergency lighting shall be provided for the stairwell, elevator room and its antechamber, and the inner walkway with a length of more than 20m in high-rise residential buildings, as stipulated in relevant clauses in GB 50045-95, JJ16-2008 and JJ 242-201KLOC-0/. Emergency lighting should be set up above the middle and high-rise buildings (7-9 floors).

4) High-rise residential emergency lighting distribution box should be divided into fire zones, and at least one special emergency lighting distribution box should be set in each fire zone; Residential buildings are generally divided into fire zones according to floors. However, the public area of each floor is small, and the number of emergency lights is small. If it is obviously unreasonable to set up an emergency lighting box on each floor, consider setting up an emergency lighting box every 4~6 floors.

5) The basement of high-rise residential building is equipped with equipment rooms such as power distribution room and fan room, and the first and second floors can be equipped with commercial outlets. The design drawings shall specify the design illuminance value and design power density value of these rooms, and shall comply with the relevant provisions in GB 50034-2004.

2.4 Lightning protection and grounding

Problems: wrong lightning protection classification, wrong building use attribute, imperfect lightning protection measures and wrong lightning protection downlead setting.

Analysis:

1) judging the lightning protection category of buildings should be based on two conditions: first, the importance and use attributes of buildings; The second is the prediction of the number of lightning strikes on buildings, and both conditions are indispensable.

2) Lightning protection measures are divided into external lightning protection measures and internal lightning protection measures. External lightning protection measures include roof direct lightning protection measures and side lightning protection measures. In the design, special attention should be paid to the differences between the new and old lightning protection standards in lightning protection measures, and corresponding lightning protection measures should also be considered for objects protruding from the external wall.

The Code for Lightning Protection Design of Buildings (GB 50057-20 10) puts forward for the first time that buildings should be equipped with internal lightning protection measures, and designers should clearly mark this point in the drawings.

3) Some designers have some misunderstandings about the special downlead in the new lightning protection code, and think that every lightning protection building should be equipped with a special downlead, otherwise it will violate the provisions of 4.3.3 and 4.4.3 (mandatory provisions) in the Code for Lightning Protection Design of Buildings. In this regard, Mr. Lin, the main drafter of the Code for Lightning Protection Design of Buildings, has explained in the magazine Building Electricity (No.20 12, 1): When the provisions of Article 5.3.8 cannot be adopted, a special down conductor should be set up, that is, the second or third lightning protection buildings are reinforced concrete buildings. When the connection between steel bars meets the conditions for being used as down conductors,

3 Conclusion

Housing is the topic that people are most concerned about, and the electrical design of housing is related to the safety of electricity consumption of thousands of households. This paper only analyzes and discusses several common problems in design drawings. Hope to attract the attention of electrical design colleagues. If there is anything wrong, please advise.

For more information about project/service/procurement bidding, and to improve the winning rate, please click on the bottom of official website Customer Service for free consultation:/#/? source=bdzd