(1) On "Power Load Classification" (Article 2.0 of GB50052-95.1)
1. The design document shall explain the building area, height and use of the building, and determine its nature, fire protection category and power load level; It is not only necessary to generally explain that the whole building is designed according to a certain level of load, but also to classify all power loads.
2. Wrong load classification is common: (1) For department stores, exhibition buildings and public buildings with a height of less than 24m and an area of more than 3000m2 on each floor, the outdoor fire water consumption exceeds 25l/s ... The Code for Fire Protection Design of Buildings (GBJ 16-87) stipulates that the fire-fighting electrical equipment shall be powered by secondary load, and the designer has not checked the relevant specifications or communicated with the building and water supply and drainage professions. (2) The same specification stipulates that the fire power load of factories and warehouses whose outdoor fire water consumption exceeds 30L/S should be Class II, but it is wrongly classified as Class III load; (3) The kitchen electricity and cold storage of the first and second class hotels belong to the first class load, but they are designed according to the third class load; (4) Class I and Class II high-rise buildings are divided according to the habit of 50 meters height, regardless of their use and nature. For example, an eight-story hospital with a height of 32 meters, or a comprehensive building with an area exceeding 1000m2 and a height of 28 meters, should be classified as Class I but Class II, and so on.
(2) Power supply for primary load (Article 2.0.2 of GB50052-95)
1, the "Regulations" stipulates that the first-class load should be powered by two power sources, which is generally clear to designers. The main problem is that many engineering substations are either designed synchronously or commissioned separately. In some areas, all substations below 10KV are simply designed by the power supply department, and even only the substations in high-rise buildings are reserved. This is an abnormal practice and may be violated. In this case, the designer should put forward clear technical requirements for the power supply level. If only the terminal design is done, the trustee will blindly design according to the conventional system and cannot meet the load level requirements. By comparison, the main wiring modes of the power supply and distribution system can be given, supplemented by the description of the operation mode, or each circuit can be classified according to the load level and power supply requirements in the form of a list.
2. For a class of high-rise buildings, when the diesel generator is selected as the secondary power supply of the primary load, the design should clearly require that the diesel generator is equipped with a self-starting device and can supply power within 30 seconds, so as to meet the requirements of the High Code for Fire Protection Design for supplying power according to the primary power supply.
3. When two power sources of a class of high-rise buildings are led from two feeders of a nearby switching station, it should be clear that the two power sources at the upper level of the switching station are from two different power plants or two regional substations.
(3) The problem of "emergency power supply and normal power supply must take measures to prevent misoperation". (Article 3.0.2 of GB50052-95)
1, the design document should have the relevant description of misoperation prevention measures and the design content of the drawings.
2. The design should not simply state that "misoperation prevention measures should be taken". For the first-class load, special attention should be paid to expressing the self-starting conditions of diesel generators, the electrical and mechanical interlocking conditions between main switches, and the accessories that the main switches must be equipped with. If key switches are used for mechanical interlocking, the interlocking relationship between them should be given.
3. According to Article, it is required that the self-starting signal of diesel generator should be taken from the auxiliary contact of the main switch of normal power supply, and not only from the voltage loss signal of the secondary circuit of the incoming voltage transformer on the high voltage side.
(4) Layout of power distribution equipment (Article 4.2.6 of GB50053-94)
1 and "Regulations" stipulate that "when the length of power distribution equipment is more than 6m, there should be two exits in the channel behind the cabinet (screen)", and the violation usually occurs when the transformer and low-voltage cabinet are combined (or there is a gap between them, but it is less than the width of one exit). Some people mistakenly think that the "Regulations" only refer to low-voltage distribution devices, ignoring that the "Regulations" also apply to 65438.
2. For strip distribution room, two or more large-capacity transformers and distribution cabinets are arranged in a straight line, and the length of emergency bus cabinets often exceeds 15m. In addition to two exits, a third exit should be added to the channel behind the screen.
(5) "About the layout of strong and weak electricity houses". (Article 4.7. 1 of JGJ37-87 Civil Building Design Guidelines)
Designers will generally pay attention to the fact that the power distribution room should not be arranged directly under the bathroom, bathroom and washroom, but they should also pay attention to other strong and weak electricity rooms, such as diesel generator room, ring network cabinet room reserved by power supply department, switch station, communication room, computer room, fire control center and strong and weak electricity distribution room, which are all rooms with moisture-proof requirements, and should not be arranged directly under the kitchen, bathroom and washroom.
In addition, the popular modular high-rise residential buildings in recent years have brought a difficult problem to the two majors of architecture and electrical engineering, that is, Article 6.2.5 of GB 50045-95 (version1997) stipulates that "no other doors, windows and walkways shall be opened on the inner walls of the front rooms of stairwells and smoke-proof stairwells except the evacuation doors leading to public walkways.
(VI) Question "It is forbidden to connect switchgear to PEN line in TN-C system" (Article 2.2 of GB50054-9512).
Violation of this "regulation" mostly occurs in the handling of TN-C-S system power supply entering households. Because some designers are not clear about the concept of TN-C-S system, when the incoming switch is 4 poles, the repeated grounding point of the pen line is connected behind the switch, which violates the Regulations. For this problem, it is often accompanied by a problem that does not meet the relevant professional standards, that is, when the residential power switch adopts a 4-pole leakage switch, the multi-line drawing is expressed as taking the pen line as the zero line, connecting it to the N pole of the switch and passing through the leakage switch, and then repeatedly grounding it. The result does not meet the requirement of clause 4.4. 17 of GB 5054-95 "It is forbidden for PE or PEN wires to pass through the magnetic circuit of current transformer in leakage protector". When the leakage switch is misoperated, the correct wiring method should be to connect the incoming pen wire to the PE grounding terminal (connected to the grounding network or MEB), then separate the PE from the N wire, and then connect the N wire to the N pole of the four-level switch. It is indicated by a single line, and the words must be clearly expressed to repeat grounding before switching.
(7) About "When installing the earth leakage switch, all live wires in the circuit it protects should be disconnected ..." (Article 4.5.6 of GB 50054-95).
The leakage circuit breaker installed in the single-phase socket circuit should be bipolar (2P or P+N), and the leakage circuit breaker installed in the main switch of residential building should be level 4 (4P or 3P+N) to prevent electrical fire. Because of the single-phase load in civil buildings, the three-phase load can not be completely balanced, and the N-line belongs to the live conductor. When the N line cannot be guaranteed to be at ground potential, the circuit breaker must disconnect it from the phase line at the same time to ensure safety. The number of poles shall be indicated on the distribution system diagram.
(8) Fire Prevention and Leakage Stopping of High-rise Civil Buildings (Article 5.3.3 of GB 50045-95 (97th Edition))
The design specification should require that the strong and weak shafts should be separated by incombustible materials equivalent to the floor fire resistance limit after the equipment installation, and the holes communicating with rooms and walkways should be filled with incombustible materials. Some designs are not explained, or although they are explained, the explanation is incomplete.
(9) The problem of "total equipotential bonding" (Article 4.4.4 of GB50054-95)
The design document should not simply say "general equipotential bonding should be done", but should put forward the practice requirements in combination with the engineering practice, and the grounding plane should also be expressed in place. According to the national standard atlas 97SD567 "Equipotential Bonding Installation", page 7, this is good, but for large-scale projects, it is difficult to connect galvanized flat steel embedded in the total equipotential terminal box (MEB) to all the bonding objects at one time (because the position of related equipment is not necessarily determined). I think "MEB" can be set at the power inlet box of substations or buildings in large-scale projects. To be reliable, MEB must be connected to the grounding grid at two points. The main reinforcement in the ground beam can be connected by MEB; φ 16, each grounding embedded block or steel bar tap is led out by reliable welding. The effect can be regarded as the national standard and atlas method, which saves labor and materials, and the hidden steel bar in concrete foundation beam is not easy to rust, ensuring reliability. MEB reserved terminals can be connected to adjacent connection points or used as backup.
It must also be reminded that many high-rise buildings' HVAC and water supply and drainage shafts should also reserve the general equipotential connection points, which are also used for lightning protection and grounding.
(10) About lightning protection (Articles 2.0. 1, 3. 1, 3.3. 10, 5.2. 1).
1. Many projects do not specify the lightning protection category of buildings.
2. For projects that may be between Class II and Class III lightning protection buildings, such as large-area multi-storey public buildings or commercial and residential buildings, the "estimated annual lightning strikes" should be carefully calculated, and the lightning protection category of the project should be determined according to the calculation results and specification requirements. It is not advisable to design according to the three types of lightning protection buildings at will, and some single-storey buildings may be "illegal" even without calculation.
3. The "Regulations" require all kinds of lightning protection buildings to take measures to prevent the invasion of lightning waves, and the specific requirements shall be implemented according to all kinds of lightning protection measures in the specification. Part of the project adopts low-voltage overhead incoming line, and the design does not require "installing lightning arrester at the entrance and connecting it to the grounding device of electrical equipment with insulator iron feet and hardware fittings"; If the incoming and outgoing lines use armored cables (including cables for electrostatic and control systems), there is no requirement for "cable inlet and outlet ends, steel pipes, etc.". Are connected to electrical equipment through grounding ",which is against the regulations. In addition, we should also pay attention to prevent the invasion of high-thunder radio waves. Used for electrical equipment fixed on the roof in the open air, such as cooling tower motor, aviation obstacle light, roof floodlight, positive pressure fan, exhaust fan, etc. , corresponding measures should be taken for its distribution lines. See article 3.5.4 of GB50057-94 for details.
4. In the design of lightning protection measures for Class II lightning protection buildings, a considerable number of designers still follow the provision of "Equalizing rings for every three floors above 30 meters" in the Code for Electrical Design of Civil Buildings, but they have not correctly implemented the provisions of Article 3.3. 10 of the Regulations. In particular, the fourth item "The top and bottom ends of vertically laid metal pipes and metal objects are connected with lightning protection devices".
5. As a lightning arrester, the provisions of the old and new specifications are different. The new specification is GB50057-94. For example, the second-class lightning protection building is ≤ 10× 10m or 8× 12m, while the electrical design code for civil buildings is 15× 15m.
(Xi) Particularity of elevator power supply (Articles 2.0. 1 82-93 of the Regulations).
1. In order to ensure the safe operation of the elevator and avoid interference from other electrical equipment, the Regulations emphasize that "the power supply of the elevator should be dedicated and sent directly from the building distribution room to the machine room", that is, the power supply line should not carry other loads. In some projects, the elevator distribution box is equipped with positive pressure fan, pressure stabilizing pump, elevator room lighting, socket, elevator shaft lighting, aviation obstacle lights, exhaust fans and other power supply lines. , not only violates Article 2.0. 1 of the Regulations, but also violates Article 2.0.3 of the Regulations, which stipulates that the lighting power supply of the machine room is separated from the elevator power supply. At the same time, it doesn't conform to the stipulation that "special power supply circuit should be used for fire-fighting electrical equipment" stipulated in Article 9. 1.3 of GB50045-95, and it doesn't conform to the stipulation that "lighting in the well should be obtained from the lighting circuit of the machine room" stipulated in Article 2.0 of GB 50182-93-93. According to "Interpretation of Articles", "Computer room lighting should belong to architectural lighting", so the design can consider setting lighting boxes in the computer room to distribute the lighting of the computer room, sockets and shaft lighting. Power supply for high-rise buildings can be provided by emergency lighting boxes, and circuits should be connected from the building power box for multi-storey buildings.
2. Some designs put the elevator power box deep in the machine room, which violates 2.0.5.3's "regulation that the position of the main switch should be accessible from the entrance of the machine room".
3. The design should know the maximum load current of the elevator (provided by the sample of the equipment manufacturer) and select the main switch correctly. It is especially important to note that when using the knife to fuse the switch, the fuse current should be able to avoid the peak current of frequent start of the elevator. When using the air switch, the switch with motor protection characteristics should be selected. In some designs, it is against clause 2.0.5. 1 to select the fuse with lightning protection characteristics according to the long delay current value of air switch.
(xii) On the illuminance standard (Articles 2.2. 1 33-90 of the Regulations).
During the review, it was found that most violations occurred in the lighting of office buildings and reading rooms. Because the lighting of offices and meeting rooms has always been designed in place at one time, its illumination standard has been included in the Regulations, and the minimum is 100LX. However, many designers are too arbitrary to arrange a few fluorescent lamps casually, which is far from the minimum standard of 100LX. In addition, the illumination in the reading room of the school library did not reach the minimum standard 150LX stipulated in the Regulations. By the way, although school lighting is not included in the Regulations, the illumination standards of classrooms, computer classrooms and other places in schools should meet the minimum standards of corresponding specifications, which should be paid enough attention.
(XIII) On fire protection design
Except for the part where automatic fire alarm devices should be installed in the High Code and the Low Code and the part where emergency lighting is required in the Regulations, there are few contents about fire protection design, so there are relatively few violations of the Regulations, but there are still many violations of relevant professional norms, so I will not repeat them here.
What must be paid great attention to now is the Code for Design of Automatic Sprinkler Fire Extinguishing System, which was promulgated on April 5, 2000 1 year and implemented in July1year. Articles 6.2.7, 6.3.3,11-1-11.0.5 of GB50084-200 1 are all listed as compulsory provisions related to electrical specialty. Compared with the same code (version 87) and Code for Design of Automatic Fire Alarm System (GB50 1 16-98), this regulation puts forward a series of new stricter and more specific regulations. Because these "Regulations" appeared in the water conservancy professional norms, a considerable number of designers of design units did not notice them, or their understanding and implementation were not in place, which became a common and prominent problem of violating the "Regulations" in the near future. Its main manifestations are: (1) the pressure switch of wet alarm valve (or the pressure switch of deluge valve group of spray system when it is also used as spray pump) is not realized, and its action signal is directly led to the pump power box or the linkage cabinet of fire control center with solid line to automatically start the spray (fog) pump; (2) The fire control center failed to monitor the water level of the fire pool and the fire water level of the roof fire water tank (note that it refers to the high water level, that is, to ensure the fire water consumption); (3) The fire control center should monitor the main and standby power supply of the spray pump; (4) When it is used as a spray pump, the control and state feedback of the solenoid valve of the deluge valve group in the fire center and the water pump room are not realized; (5) The fire alarm system did not monitor the status of the signal valves at the inlet and outlet of the wet alarm valve. The design of these contents involves the wiring diagram of pump control principle, fire alarm, linkage system diagram and fire protection layout diagram of Qiangdian Power Company, which needs close cooperation with water affairs specialty. However, many design units only send a simple text modification notice after receiving the review report, which can not meet the design depth requirements. The above questions remind us that we must pay close attention to the newly released information of Mandatory Provisions, and at the same time, we can't ignore the contents related to electrical specialty in the Provisions of related majors.
Summary:
Through the review of construction drawings, it is also revealed that some people in our design team are not strong enough to learn and implement specifications; Even some professional basic concepts are unclear and have little knowledge; There are also some people who have a weak sense of responsibility and are full of mistakes; Of course, objectively, some designs are too short and drawn in a hurry. However, it should be noted that construction drawing review has become a necessary procedure for basic buildings. Unlike the previous annual inspection of design quality, there is no luck. Every designer must face it seriously. Although the current review focuses on the violation of "mandatory provisions", the above list is only "common diseases", and it also involves related professional norms and serious design depth issues. Because it is a "peer review peer", this has to be a great touch and pressure on designers. While everyone is complaining that "design is getting harder and harder to do", we will be delighted to find that designers and examiners pay more attention to normative study, research and communication than before, and the problem of violating "mandatory provisions" in exams is gradually decreasing. Although due to the level of examiners, there are differences in grasping the standards, and the "lag" of some standards will cause controversy on some issues, which is hard to avoid in the near future, but it is also a good thing in a sense, which promotes the formation of a good academic atmosphere for learning, research, discussion and even debate in the design field. The views I expressed above may also be inappropriate or even fallacious. I think it's just to attract jade, hoping to trigger a wider wave of learning and discussion, so as to achieve the goal of * * * promotion.
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