Keywords: integrated design type selection verification system model
Pivotalwords: integrated design, selection and verification of equipment types, and construction of power system model.
I. Introduction:
In the field of engineering electrical design, the calculation and verification of power system equipment selection is undoubtedly the most complicated and tedious work. The complexity of the problem lies in the reliability requirements of power system operation. All equipment, such as high and low voltage distribution equipment, substations, transmission cables and other equipment, must be calculated and checked, taking into account the safe and reliable operation of equipment under various operating conditions and the reliable operation in short circuit. Because there are many devices, circuits, systems and calibration items, the work is complicated. At present, there is no software in China to simulate the thinking of electrical engineers for automatic selection, calibration and calculation, instead of some work, which really liberates electrical engineers from tedious calculation and drawing. The latest scientific research achievement of our company-integrated design software of power supply and distribution system just fills this gap.
Second, detailed:
The goal of electrical design
Only when we know the ultimate goal of electrical design can we do more definite work. In order to explain all the electrical contents of a substation in detail, we usually need to draw the following drawings:
1. 1 electrical main wiring diagram or high voltage system diagram
1.2 low-voltage system diagram
1.3 layout and profile
1.4 front view of power distribution cabinet
1.5 cable list
1.6 list of equipment and materials
1.7 electrical calculation table
1.8 schematic diagram of secondary control
1.9 secondary external circuit diagram
Among the above drawings, the most complicated drawings have the largest workload, because they occupy a lot of calculation workload. In the past, we also provided some calculation tools and software, but most of them were scattered and unsystematic, such as load calculation, voltage loss calculation and short circuit calculation. Users' understanding of the whole system has been stuck in low-level labor such as modifying old drawings, repeatedly calculating-filling in forms-replacing equipment-deleting-copying, which leads to the inability to greatly improve labor efficiency. Moreover, due to the lack of understanding of the structure of the whole power supply and distribution system, the switch at the next level has not changed after the adjustment of the switch at the next level, or the setting of the switch at the next level has changed, and the wiring has not been adjusted accordingly, resulting in many inconsistent wrong drawings and problem projects. A large number of graphic elements in old drawings are independent and not * * *, so it is difficult to modify them successfully on a large scale at one time. There is a lot of repetitive work in modifying old drawings, and repeated commands such as deleting, copying, replacing, writing and moving are easy to cause clerical errors. In particular, the current engineering design cycle has been greatly shortened by the owners, and how to improve the efficiency of design and drawing has become a key issue.
Present situation of drawing calculation software
At present, domestic electrical design software mainly provides drawing function for this part. A scheme of drawing high and low voltage cabinets, many manufacturers' software includes this part of the gallery. Our drawing is mainly to insert the corresponding blocks for drawing, and then fill in the order drawing form. The calculation is separate.
There are also some softwares that provide partial calculations for high and low voltage systems, but most of them are piecemeal, not for the whole system, nor for a certain loop or a certain load type (such as motors). Other circuits or load types can not be calculated, nor can they be selected with the cooperation of superiors and subordinates, nor can they comprehensively check all technical parameters of electrical equipment, and there is no electricity demand table, which is too different from the design process required by the actual project. Therefore, in the process of substation design, most of the work is still focused on modifying the old drawings and recalculating the selection. The function of computer aided design has not been greatly improved.
Process analysis of electrical design
Uniform provisions on model selection
Many design institutes have adopted the selection scheme in the collaborative design of a project, such as KYN28 for high-voltage distribution cabinet, MNS for low-voltage cabinet, CM 1 for main circuit breaker and VV series for cables. This option is the same in the same project. It can also be applied to the next project.
Definition of power demand
The electricity demand provided by upstream specialties such as water, heating and technology mainly includes electrical design requirements such as the serial number, equipment name, installation location, rated voltage, load grade, site attributes and load nature of electrical equipment.
Nowadays, with the popularization of computers, many design institutes use EXCEL to extract information from each other.
Load distribution
Determine the position of distribution equipment (distribution box, panel, cabinet) and assign each load to the distribution equipment.
Load calculation
Calculate the load of each power distribution equipment. The demand coefficient method is mainly used.
Calculation and selection of distribution center
The power distribution cabinets in the power distribution center (such as the power distribution room of a certain floor, vertical shaft, or the power distribution room in the machine room) supply power to the lower distribution board or distribution box. Select these switchboards, boxes and cabinets.
Calculation and selection of distribution center
The distribution center supplies power to the distribution center. All equipment in the power distribution center, including bus bars, high-voltage cables, high-voltage cabinets, low-voltage cabinets, low-voltage drawer components and low-voltage outgoing lines, are selected.
Short circuit calculation
After the selection is completed, the impedance of each component and cable is obtained by looking up the table, and short-circuit points are set to calculate the three-phase and single-phase short-circuit currents of each short-circuit point.
Check calculation
Check the short circuit, voltage loss, motor starting and sensitivity of high and low voltage equipment. Check the inappropriate values and make a new selection. Until the verification is passed.
Draw a system diagram
According to the system model, draw the system diagram.
Tidy up the cupboard.
Arrange cabinets according to the plane situation. And draw elevation and section.
According to the arrangement of cabinets, adjust the position and number of drawers in the system diagram, as well as the positions of wire entry cabinets and bus heads.
Symbol library of loop library and equipment library
The primary scheme of high and low voltage cabinets is provided by the manufacturer's samples. To call these schemes in CAD drawing, they must be organized into a circular library. Each loop consists of many components. The electrical characteristics (technical parameters) of these components are defined in the equipment library. The symbol library is a legend that specifies the corresponding relationship between these components. The above three aspects are essential in the process of drawing selection.
In order to cope with many manufacturers and different models and specifications, our symbol library, equipment library and circulation library are all open. Users can add new equipment series, new loop schemes, etc.
The symbol library adopts the new national standard legend. The loop library and equipment library also adopt the most popular and advanced models of high and low cabinets at present, especially the first and second volumes and the supplements of the latest edition of the Manual of Common Electrical Equipment in Factories published by China Building Standard and the first and second volumes.
In the loop library structure, each loop can set the model, specification, quantity or rated current of the components in the panel, and control the motor power so that it can be input completely according to the contents provided by the sample, which provides an "electronic sample" for selection.
Unified rule setting
The basic scheme of equipment selection determined by the project leader of electrical specialty before doing a project. In this basic scheme, all electrical equipment is divided into power supply, transmission, distribution and electricity consumption. Users only need to make a preliminary selection of the above equipment and determine the serial number and related parameters of the equipment. Other parameters can be selected automatically.
Power demand definition table
The electricity demand table is a list of all electrical equipment used in the project entered by the user himself. Users need to input the installation location, name number, equipment capacity, load nature and other contents of electrical equipment. You can import the data in the pipeline process from EXCEL to a table, or export the imported power demand table to EXCEL for editing. The installation location provides a good structure for managing all equipment, which is very intuitive and convenient.
Establishment of system model
The purpose and ultimate goal of this software design is to achieve the goal of electrical design. That is, draw a drawing that meets the requirements. Before drawing drawings, the power supply and distribution system must be established. The concept of integrated design has never been put forward in previous design software.
4. 1 The so-called integrated design refers to the electrical design of the whole power supply and distribution system, including a series of comprehensive and complex design processes, such as unified preliminary selection, power demand table definition, power load distribution, load calculation, selection calculation, short circuit calculation, check calculation and so on. The power supply and distribution system model can be established, and the working (running) properties, short circuit properties and electrical properties of each power supply, transmission and power consumption equipment are listed in detail on the model.
Any power supply, distribution, transmission and consumption equipment has three attributes, namely, working attribute, short circuit attribute and electrical attribute.
Working attributes refer to the working current, equipment capacity, working voltage and power factor of the currently selected equipment. The short-circuit attribute refers to the short-circuit impedance and short-circuit current of the currently selected equipment. Electrical attributes are the electrical model specifications and technical parameters of the equipment nameplate.
The process of integrated design is to manually add power load to the distribution cabinet. Then calculate the load, automatically select the model specifications of components in the distribution cabinet, and select short-circuit parameters for short-circuit verification. If the short circuit check fails, re-select the calculation.
4.2 Establishment of system model: In order to realize the overall selection, verification and design of equipment in substation, it is necessary to establish the distribution system model of the whole project, so as to realize the selection and verification of all equipment.
A good system model is intuitive and easy to operate. Do it quickly. In perfect order Because the tree structure of electrical system is similar to that of WINDOWS resource manager, we can use the tree structure of WINDOWS resource manager to build a model and realize a simple distribution system.
The most commonly used electrical connection relationships in power system are series and parallel. All complex networks can finally be regarded as a combination of series and parallel electrical equipment. As can be seen from the following figure, the relationship of component names from left to right on tree nodes constitutes a series loop: low-voltage distribution room (power supply), cable, load switch, transformer, bus bar and incoming cabinet. .....
The "3-bus drawer 2, drawer 3, drawer 4 and drawer 5" connected under the "3-bus" node are several drawers connected in parallel by buses.
The system model established in this way has the characteristics of intuitive image, simple structure and strict organization. It can completely realize all the functions of substation system design. Figure 1 The corresponding power supply and distribution system is shown in Figure 2. Attached drawing 1
Attached Figure 2
4.3 System model The functional system model is established from the power distribution center (power distribution room, power distribution room) in the project. The system model can visually see the primary scheme graphics of switchgear. In order to choose a unified model, the power demand can be uniformly distributed. Determine the power supply location of all electrical equipment.
4. The system model can calculate the load of each device. Statistical total load
5. The system model can be used for power supply load statistics and reactive power compensation calculation.
6. The system model can be used for short circuit calculation. Short circuit calculation includes short circuit calculation of infinite large capacity system and active power system. Any established model can be calculated automatically. The short-circuit impedance database can be extended.
7. On the basis of load calculation, short circuit calculation and preliminary scheme selection, the model is automatically selected and calculated. 8. After the system selection calculation, the parameters are checked and calculated, including high and low voltage equipment, distribution trunk lines and other equipment, which can be checked according to the specification requirements. The model can visually see the current working current, short-circuit point short-circuit current and equipment technical parameters of any equipment on the distribution system of the distribution center.
10. It can automatically output a series of drawings such as high and low voltage system diagram, main wiring diagram, equipment and material list, cable list, calculation book, arrangement diagram of chest of drawers, etc. Complete the whole process of aided design. Software implementation flow chart
The software implementation process is actually a simulation and abstraction of the design process of electrical engineers. This process deeply embodies the whole process of electrical design described in the third section, and simulates the design idea to carry out electrical aided design. General Equipment Selection Verification Scheme (Part) Pressure Equipment Selection: Load Distribution-> Load calculation->; Selection of low voltage bus
Load distribution->; Load calculation->; According to the normal working current.
The verification contents are as follows: motor start-up voltage drop calculation and voltage loss calculation.
3, overload protection effect
4, thermal stability effect cable conductor selection
Load calculation->; According to the normal working current.
1, effective voltage loss:
2, check the economic current density:
3, the effect of thermal stability.
4. Selection of low-voltage switch for overload protection
Load calculation->; Select according to normal operation: 1, shell-level current selection 2, rated current selection of release 3, rated current selection of short delay, instantaneous delay and long delay release according to loop protection setting requirements.
1, efficacy limit breaking capacity
2, the effect of breaking current
3. Efficacy sensitivity
4, the superior and subordinate cooperation effect
5, the choice of high voltage switch overload protection function
Load calculation->; Select 1 according to the normal working current, and select the rated current to verify the breaking current or breaking ability. Maximum working voltage, dynamic stability and thermal stability are verified. Advantages of 10 integrated design software
1. realizes the real power supply and distribution system model, and is an electrical design software for the whole power system. Different from the scattered isolated modules in the past, this advantage is that electrical engineers can intuitively and clearly understand the position, function, running state, short circuit state and all electrical characteristics of each electrical component in the power system.
First, carry out load calculation, short circuit calculation, type selection calculation and calibration calculation. The four major calculations are integrated into one, and the selection results are clearer.
2. This design is convenient for load adjustment, circuit replacement and modification of equipment technical parameters. Provide a series of intelligent detection systems to ensure the correctness of cascade relationship and electrical circuit parameters.
Integrated design facilitates the output management of cable list and equipment list.
Integrated design provides an extensible loop library and equipment library, which are completely modeled after equipment samples and are all open. Users can add new devices.
Integrated design provides users with the most convenient and direct query function. Click on any device component on the system model to see the voltage, current and power of the device. You can also see the short-circuit impedance and short-circuit current at this point, and even query the short-circuit current at other points.
The interface of integrated design adopts resource manager interface, and anyone who knows windows can build a system model. There is no need to increase study time. The operation is similar to the resource manager, which is extremely easy to use.
The comprehensive design provides many commonly used methods for selection, verification and calculation of power supply and distribution equipment. Users can use a certain method to check, or they can use all of them to check as needed. Very flexible.
Integrated design is a cad electrical design software for electrical equipment. Unlike before, it doesn't need to draw a little piece, copy and paste. Electrical engineers only consider the content of electrical design, and other commands and operations related to drawing and any line elements do not need to be considered. This is a real electrical design expert system.
The integrated design completely refers to the latest version of electrical specifications, design manuals, unified technical measures and mandatory provisions and the latest version of electrical equipment manuals. Keep pace with the times.
Three. conclusion
Load calculation, short circuit calculation, type selection and calibration calculation of substation are one of the most complicated contents in electrical design. We design and implement the expert system by using CAM/CAD software, which is the first attempt in the electrical design industry and has important historical significance and wide practical value. It means that domestic electrical design CAD will break through the original trend of redrawing and neglecting aided design, and take a gratifying step towards a more intelligent electrical design expert system.
Bibliography:
Handbook of Industrial and Civil Distribution Design, 2nd Edition, edited by China Aviation Industry Planning and Design Institute, Water Conservancy and Electric Power Press.
Example Atlas of Building Electrical Design, edited by Design Committee of Beijing Lighting Society, China Building Industry Press.
Handbook of Common Electrical Equipment in Factories compiled by the Fifth Design Institute of Ordnance Department, China Electric Power Press.
Hunan Electric Power Information Network "Civil Building Electrical Design Manual" China Building Industry Press
Code for Design of Low Voltage Distribution (GB50054-95) China Planning Press.
Code for Design of Power Supply and Distribution System GB50052-95 China Planning Publishing House
Code for electrical design of civil buildings JGJ-T 16-92 China planning publishing house