What aspects of the basics of electricity do you need to know to be a good electrical designer (the more detail the better)?

. Introduction Engineering design is the leader of the capital construction, design documents are the main basis for engineering construction, design quality is to determine the quality of the project is the primary link. China's engineering quality accident statistics show that the design causes engineering quality accidents accounted for 40.1%; engineering construction causes 29.3%; other reasons (such as equipment and material quality problems, etc.) caused by 30.6%. Visible to the implementation of three control of project quality is the key to design quality control. Electrical engineering is no exception.　　My company was created in 1994 with double A qualification construction supervision company, over the years has undertaken hundreds of civil construction projects and municipal engineering construction supervision and design supervision tasks, the completed project in the pass rate of 100%, the good rate of 57% or more. In the construction process of the project undertaken, found and dealt with a large number of engineering quality problems, mostly related to design quality issues. Now combined with engineering examples, the main building electrical design problems and countermeasures affecting the quality of electrical engineering is discussed.　　 2. Several building electrical design problems affecting the quality of the project Qualified building design should meet the requirements of the seven quality characteristics specified, namely, functionality, safety, economy, credibility, implementability, adaptability and timeliness. The design unit should have passed the design review of the qualified design documents delivered to the construction. In fact, many of the design documents delivered to the construction have defects that lack or deviate from the quality characteristics required. The quality of electrical engineering design issues affect the main performance in the safety, reliability (including availability, reliability, maintenance, etc.) and implementability of the lack of or deviation. Several of the most common aspects are discussed below.　　2.1 design violation or deviation from the provisions of the design specifications, safety, credibility of the phenomenon of non-execution of the design specifications is quite common For example, a municipal government building in front of the garden plaza (including plaza green garden lighting, lawn lighting and plaza center sound and light fountains) project submitted to the construction of the electrical construction drawings there are the following problems: no electrical protection grounding and equipotential linkage design; incorrectly using TN C low-voltage power distribution system; fountains are not required to choose the level of protection of electrical equipment and cables. Such a design is completely contrary to the safety requirements of the specification, according to the construction of the plan will leave serious safety hazards. Previously, in August 1999, Qingdao City, a fountain has occurred in a number of people playing in the water was electrocuted to death casualties, it is due to design errors, underwater lamps and lanterns and submersible pumps leakage and failed to cut off the power caused by timely. Supervision in the pre-construction review and found the above problems, through the owner requires the design unit in strict accordance with the design specification requirements to modify the design. The correct approach is: outdoor courtyard and fountain power distribution should be used local TT system or TN-S system, and set up leakage protection (action current should not be greater than 30 mA), and does not allow the use of TN-C system; should be set up to improve the grounding device, the fountain should be done to equipotential linkage design, rather than relying on the building from a lead out of the PE trunk line grounding; submersible pumps and submersible fixtures. PE trunk grounding; submersible pumps and underwater lamps and lanterns should be used submersible cable distribution; 0 area electrical equipment should be used 1P × 8 level of protection, 1 area should be 1P × 5 and so on.　　Another example of civil buildings, low-voltage distribution line cross-section selection issues. As the vast majority of civil building electricity load for single-phase load, three-phase load imbalance will inevitably lead to unbalanced current through the center line; with the development and popularization of computers and various household electrical equipment, low-voltage power grids, high-level harmonic pollution is increasing, the 3rd and its odd multiples of harmonics are composed of neutral current. Neutral overcurrent and the resulting phenomenon of electrical fires is also increasing. For this reason, the relevant design specification has stipulated that "three-phase four-wire or two-phase three-wire distribution lines, when the majority of electrical loads for single-phase loads, its N line or PEN line cross-section should not be smaller than the phase cross-section; gas discharge lamps as the main load in the circuit, the N line cross-section should not be smaller than the phase cross-section of the line ...... ", it can be seen, civil buildings power distribution system trunk line, branch trunk line and branch line of the conductor cross-section in principle should be selected N or PEN line cross-section and phase line cross-section of the same. However, the supervision of the map found that there are still a lot of civil buildings power distribution design is still used in the 80's has been used before the practice, the selection of N or PEN line cross-section is still 1/2 or even 1/4 ~ 1/3 of the phase line, which is also one of the most common electrical design safety issues.　　Another example, on the choice of the location of the substation, the relevant design specifications are clearly put forward should be considered "equipment lifting and transportation convenience", which is to ensure the availability and maintenance of the basic requirements. In recent years, we are responsible for the supervision of a number of high-rise building projects, which are set up in the ground floor of the substation and diesel generator room configuration more than contrary to this requirement. For example, a high-rise commercial and residential building underground power distribution and generator room, its transportation access is completely blocked by the chiller and underground water tank. Construction and installation sequence can only be the first variable, power distribution equipment and power generation group installed in place before installing chiller and water tank, and did not consider the operation of power generation and substation equipment maintenance, replacement of transportation issues; and a high-rise office complex underground power distribution and generator room, set in a conference hall at the bottom of the first floor, the ground floor is not considered the necessary transportation and maintenance access, but also did not set up a sufficient width of the door frame can be transported into the equipment. When the supervisory review found and put forward this problem, the design unit's answer is: the original design intention is a conference hall will be lifted from a floor of power distribution and power generation equipment in place and then poured the floor of the hall. This intention is obviously wrong, even if we do not take into account the civil construction may have been in place of the electrical equipment caused by the damage, the building put into operation after the electrical equipment maintenance and replacement of transportation is only to pry open the floor of the first floor of the conference hall to solve it! It must be known that the reasonable service life of reinforced concrete frame building up to 50 years or more, while the service life of the power distribution equipment is only about 20 years or less, regular or faulty maintenance cycle is even shorter. Therefore, the electrical design must properly consider the transportation and maintenance of lifting access.　　2.2 Design depth is not enough At present, the construction drawings design depth does not meet the requirements of the Ministry of Construction, "Construction Engineering Design Document Preparation Depth Provisions" phenomenon is quite common, mainly the design documents can be implemented in the implementation of the defects will directly lead to the construction and installation of the difficulties or errors. It may also lead to lack of usability. Due to the depth of the required calculations and labeling, but also often lead to the design documents themselves appear in principle errors and difficult to find in time, will affect the use of the completed project function.　　For example, according to the depth of the provisions of the power and lighting system diagram and the corresponding equipment and materials table should be marked in detail the selection of electrical equipment and materials, model, name, specification parameters and quantity. Since the reform, China's electrical products market colorful, a variety of domestic and foreign models and specifications of a wide range of products, the state is not possible for all types of electrical equipment and materials to provide a uniform model. Designed to indicate a variety of equipment and materials model specifications parameters will be particularly important, which is the owner or construction unit for equipment ordering and procurement basis. However, in recent years, electrical design documents are generally accustomed to only in the system diagram of the equipment symbols next to the labeling of the equipment model or manufacturer's product number, so that the equipment ordering at a loss, and often lead to errors. For example, a project electrical lighting design, the designer in the system diagram next to the circuit breaker symbols only marked "A063M20A", the equipment table is also the same, but did not specify the name and detailed parameters, the construction unit is understood to be a 20A ordinary circuit breaker, due to the number of products can not be found and purchased separately another circuit breaker. After the equipment and materials inspection by the supervisory staff to check, it turned out that "A063M" is a Hager electromagnetic earth leakage circuit breaker product number, rated current 20A, rated leakage action current value of 30mA. visible in the original design of these circuits should be equipped with earth leakage protection. But because the design is not clearly labeled and cause ordering errors. Only have to re-purchase replacement; Another example is that many electrical construction drawings of the cable trench only marked size and direction, the cable bracket and cover does not make any provisions, or only indicate "refer to × × × atlas × × × page", in fact, the national standard atlas of any size of the cable trench, the cable bracket and the cover of the way to provide a number of programs for design Choice, the design is not selected by the construction side is difficult to choose, often according to the lowest price program construction. Often does not meet the actual needs, and may even cause settlement disputes.　　Again, such as electrical lighting diagrams in accordance with the provisions of the main rooms and places should be labeled illuminance standard values, of course, also requires the designer to carry out illuminance calculations and calculations for the configuration of lamps and lanterns. However, the current civil building electrical lighting design can be labeled illuminance standard values and illuminance calculations are extremely rare, the vast majority of housing and function according to the opening of the light by experience. Most of the deviation from the national illumination standards, affecting the use of function. For example, by the supervision of the electrical construction plans of a school, the accounting design to achieve the illuminance value of laboratories and classrooms is only 50 ~ 70lx, less than half of the national standard; a bureau of office buildings in the office and conference room design illuminance only up to 70 ~ 80 lx, the computer room is only up to about 100 lx or so. Less than half of the national standard illumination value.　　2.3 related professional design documents are not clear, not in accordance with the provisions of the coordination and cooperation of the problem prevails, is very likely to lead to construction errors For example, the current widespread use of building structural reinforcement as a lightning connector, lead wires and grounding and equipotential bonding device, according to the regulations should be labeled in the electrical construction drawings of the joints, pre-embedding, laying methods and technical measures (such as welding requirements, etc.); and in the civil engineering drawings have related to the pre-embedded parts detailed drawings and the relevant Embedded parts of the civil construction drawings have relevant detailed drawings and related markings and instructions. In fact, most of the construction drawings only in the electrical diagrams in the lightning protection grounding map, and labeling and description of the rather brief, civil construction drawings are often without any relevant description and labeling. This brings great difficulties to the project supervision and construction, if the construction unit is inexperienced, it is very easy because of the type of work (sequence) with the improper construction errors and omissions. The most common is the connection point of the grounding reinforcement mesh error, leakage of welding and as the external lead grounding connection point or detection point of the omission of pre-buried parts. Especially in the conversion layer of the building structure, due to the adjustment of the main reinforcement in the column (wall), the lightning protection lead wire reinforcement misconnection and miswelding is more likely to occur.　　Another example is that the professional pipelines, lines collide with each other, contradict each other's problems have become construction drawings of multiple diseases, abound, to name a few. We are responsible for the supervision of several buildings of the underground floor (including underground garage) construction plan design, the review of drawings have found: water supply and drainage pipes and ventilation, exhaust ducts and lighting fixtures and electrical piping in many places touch; multiple fire detectors were ventilated, smoke ducts blocked; only to modify the design and then construction and installation; and then, as a residential community due to the original design of water supply and drainage and electrical specialties failed to coordinate the completion of the project was completed only to find that the initial inspection Almost every set of indoor air conditioner installation at the reserved drainpipe and through the wall holes and air conditioning power sockets were located on both sides of the window wall, that is, the air conditioning installation location and sockets are not in the same place, the socket can not be used, and had to rework the re-installation.　　3. Conclusion design documents is the construction and supervision of the most important basis for the design can seriously implement the national regulations, the depth of the design documents and related professional close cooperation issues, etc. have a direct impact on the quality of the project. In recent years, the design quality of the phenomenon of slippage has become an indisputable fact, the reasons for which may be manifold, such as the design of the market price competition, forcing the design unit to reduce inputs in order to reduce costs, etc., this paper does not intend to explore. The above only from the construction and supervision point of view common design problems. And this kind of problem is not a chronic or persistent disease, as long as the design unit a little attention, such as the organization of the design staff to seriously study the relevant design specifications, strengthen the design process management, pay attention to the design of the countersigning and review, can be basically cured. And engineering supervision and engineering construction will benefit greatly.