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Designing of a distributive network of system of an electrical supply of industrial targets: ElectriCA
This article is an example of the interaction of different programs for design solutions, designed in the form of project documentation to power the electrical part of complex industrial projects.                         

Designing of a distributive network assumes the decision of some the interconnected problems which in case of difficult industrial targets can dare different groups of experts. Designing of system of an electrical supply consists of following stages.

1. Definition of electric loadings taking into account operating modes and spatial placing of consumers of electric energy. At this stage preliminary working out of structure of a network is carried out; the necessary number of power supplies and transformers is estimated; preliminary distribution of consumers on levels is carried out; the preliminary structure of the electrotechnical equipment of a network is defined.

2. Working out configurations of the scheme of a distributive network . Here the problems connected with are solved:
     – definition of settlement loadings of elements;
     – pressure losses in normal modes, at start-up and self-starts;
     – levels of the maximum currents of short circuit for check of firmness of the equipment;
     – levels of minimum currents of short circuit for check of sensitivity of protective devices.
Besides, the capital equipment choice on rated currents, on firmness to currents of short circuit, on pressure losses is carried out. Thus, the complex of questions of functional aspect of a network, and also preliminary placing of switching centers in space of buildings and constructions dares.

3. A choice of the capital equipment of a network taking into account its design concrete manufacturer. At this stage the choice of blocks of management and cases of switching centers taking into account the problems formulated at designing of the basic technological process and according to the accepted scheme of a distributive network is carried out. The situation when design the organisations are prepared only by the task for manufacturer where the given problem and is carried out in full is possible. At a choice of standard blocks it can appear that the decisions accepted at the previous stage, it is impossible to realise. Specifications of schemes and, accordingly, repeated calculations In this case will be necessary.

4. Capital equipment placing in space of premises and definition of cable lines. This stage can be carried out in parallel with the named stages as a part of a problem of placing of the process equipment. Cable lines are outlined on early design stages. Even at process equipment placing the place for switching centers and control means is provided, and also spaces for cable lines are defined. Questions of definitive placing of the electrotechnical equipment dare after placing of the process equipment and a choice of structure of switching centers.

5. An apportion of cables on lines. At designing of power objects the apportion power, control, cables and communication cables on lines is made, as a rule, for one operation after a definitive choice and placing of the technological and electrotechnical equipment, performance of the project of management information system, systems of fire safety, system of the security alarm system, etc. For performance of procedure of an apportion the information on cables of all systems gathers. If the control system project technological process and a choice of the equipment of switching centers can be carried out by suppliers of the equipment the cable apportion is carried out only by divisions and the organisations responsible for designing of an electric part of object.

6. Formation of custom-made specifications on the electric equipment and cables. As a rule, this stage should be carried out after end of a choice of the equipment and a cable apportion, however in modern conditions for reduction of the general terms of a construction of difficult industrial targets and maintenance of the order of the equipment custom-made specifications should be let out on early design stages, and then repeatedly them to specify.

The above described sequence can be presented the block diagramme represented in drawing.

The block diagramme of sequence of design procedures at designing of an electric part of an industrial target


It is supposed that the technological scheme is formed with use of the special software (PLANT-4D P& ID, PDS 2D, SmartPlant P& ID, etc.). The list of the electrified equipment moves in electronic form as the design assignment of an electric part, measuring instrument and the management information system.

For performance of working out of a configuration of a distributive network and performance of complex calculations it can be used EnergyCS the Electrician – considerably an improved version delivered before program ElectriCA.

The program allows to solve following problems:
- Definition of settlement loadings for all elements of a distributive network various methods, including presented in “Instructions by calculation of electric loadings Guidance and technical documents 36.18.32.4-92”;
- Calculation of working currents in phase and zero wires of a four-wire network on the set loadings, calculation of phase and linear pressure in each point of a network, and also definition of the greatest deviations of pressure in the established mode;

- Calculation of streams and capacity losses in all elements of a network in the established operating mode;
- Calculation of size of thermal emissions in conductors and an electric equipment in the set premises;
- Calculation of peak (starting) currents and time of their course in all elements of a network, and also pressure in each point at course of peak currents with an estimation of the greatest deviations of pressure from rating values;
- Definition for each element of a network of the maximum currents during the initial moment of time at three-phase and single-phase КЗ and the greatest value of shock current of short circuit. For three-phase of short circuit possible feeds from synchronous and asynchronous engines taking into account parametres of the established mode previous of short circuit are considered;
- Definition for each element of a network of the minimum currents at single-phase, diphasic and three-phase of short circuit taking into account resistance of an arch, and also heating of current carrying parts by a working current and current of short circuit (the account of thermal recession);
- Definition for each possible point of short circuit of time of switching-off according to the set characteristics of operation of the basic and reserve protective devices;
- An estimation of temperature of veins of wires and cables at working currents and during the moments of switching-off of currents of short circuit the basic and reserve protection for check of cables on thermal firmness and no fire;
- An automatic choice from the built in database of sections of wires and cables, switching and protective devices;
- Check of selectivity of operation of protective devices with the characteristic of time of operation dependent and independent of a current, and also construction of cards of selectivity;
- The automated choice of setpoint automatic machines and rated currents of fusible inserts of safety locks;
- Calculations for networks of a direct current with storage batteries: calculation of loadings, calculation of maximum and minimum currents of short circuit.

All complex of calculations is carried out on uniform computer model and allows to consider set of shemno-regime conditions. For entering into the scheme of updatings by simple enough pressing of a key of the mouse to change a condition of switching devices.

The program can be used and as an independent product for performance of complex calculations, and as to a component of system of the automated designing. In the first case all data is entered manually with use of graphic and tabular editors. In the second formal input of the information on the list of consumers of electric energy is carried out from CAD technological process.

The initial data for program complex ElectriCA are lists of consumers of electric energy (with instructions of requirements to their electrical supply), premises, possible power supplies, and also the catalogue of the equipment with the necessary help information.

The block diagramme of an internal database of program ElectriCA


The list of consumers of electric energy can be presented in the tabular form.

The information volume in the list of consumers should be sufficient for designing of an electrical supply of object and its connection to the automatic control system. As a rule, here following data are displayed:
- A designation;
- A group code (a sign of identity of parametres of the several consumers carrying out identical function and having identical parametres);
- the name;
- rated power;
- rated voltage;
- a power factor (cosφ);
- factor of loading of the device;
- a starting current of the device;
- expected time of start-up at rated voltage;
- expected time of start-up at the lowered pressure (80%);
- the information on an operating mode;
- necessity of participation for self-start;
- a sign of necessity of management from central DCS;
- a sign and a way of local management;
- presence of the emergency local button of Feet;
- factory type of the engine (if it is defined);
- an operating mode of the device, etc.

The part of these parametres is necessary for calculation performance, and the part is intended for transfer on the following design stage (for example, for a choice of blocks of management and the decision of design aspect of designing of switching centers).

At input all electroreceivers share on groups by a principle of similarity and possibility of mutual reservation. So, if three pumps are necessary for maintenance of normal technological process, and on conditions of maintenance of demanded level of reliability and reservation the decision on installation of five all these five pumps form one group is accepted. In the table of groups all key parametres of consumers of electric energy, and in the table of electroreceivers – only individual parametres of each pump (for example, a unique designation, spatial coordinates (X, Y, Z), etc.) contain.

In the beginning of designing of a network it is necessary for designer to distribute electroreceivers on power supplies, and single-phase – also on phases. In the first case necessity of a food interaction reserving technological devices from two different independent power supplies should be considered. The power supply in the program is understood as a power supply system: a higher network, the independent generator, the storage battery. Communication with system, as a rule, is carried out through lowering transformers. At distribution of loadings uniform loading of transformers should be provided. From independent generators and storage batteries the most significant electroreceivers demanding a guaranteed food eat.

Results of an estimation of settlement loadings allow to estimate at once congestion of the consumer, and also necessary capacity of the lowering transformer and independent energy sources.

At distribution on phases it is necessary to provide single-phase electroreceivers with the uniform loading defined as a result of calculation of modes.

The problem of the designer at a stage of functional designing of the scheme of an electrical supply consists in working out of a configuration of a network and a choice of the equipment, capable to provide the set functional characteristics:
- a reliable electrical supply of all electroreceivers presented in the initial data;
- factors of loading of all network equipment taking into account the amendment on an ambient temperature according to the task;
- uniform distribution on phases at asymmetrical loading;
- conformity of deviations of pressure in all normal and post-accident modes, and also at normal start-up of mechanisms to the pressure stipulated in the task; possibility of their adjustment by the provided means of regulation of pressure;
- thermal firmness to the greatest currents of short circuit during time of action of the basic protection, excluding the failures connected with ignition of cables, at refusal of the cores and operation of reserve protection;
- firmness to dynamic influences of currents of short circuit;
- sensitivity to is minimum possible currents of short circuit which should be disconnected by corresponding protection;
- a coordination of protection of different level on selectivity.

Performance of the listed conditions is often complicated by that they can contradict each other. As practice shows, at designing without similar programs, as a rule, all complex of requirements is not carried out: or it is supposed nonselectivity in separate parts of the scheme, or the equipment somewhere appears unstable at refusals of protection, etc.

Such errors of designing come often to light and corrected in the course of starting-up and adjustment works, but can remain not noticed with all following consequences.

In EnergyCS the Electrician input of a configuration of the scheme is carried out with use of the built in graphic editor. Thus calculation of a mode of already entered part of the scheme and specification of its parametres is at any moment possible.

The scheme of an electrical supply of pump station (the general scheme of top level
The scheme of assemblage of pump station
The part of the scheme of assemblage of pump station


The uniform model of the scheme of an electrical supply can be presented on several sheets. Possibility to display as the scheme as a whole, so schemes of separate assemblages is provided.

In the program complex calculation is always carried out. All set of regime parametres of each element of a network on which basis the choice is carried out is at any moment accessible or suitability for performance of this or that function is checked. Estimator only operates visibility of parametres on the scheme and in tables.

Among other messages on the broken conditions the message on outstanding conditions of selectivity is deduced also.

To provide selectivity the schedule of dependence of time from a current (a selectivity card) where the following information is deduced helps.
1. A line of a starting working current loadings (red).
2. A line of a curve of operation of the basic protection of a site (the allocated protective device) taking into account its flowing setpoint (a black line).
3. A line of a curve of operation of reserve protection of a site (higher in relation to the allocated protective device) taking into account its flowing setpoint (a dark blue line).
4. Lines of the minimum currents of short circuit (single-phase, diphasic and three-phase) for the given protective device, reflecting change of a current depending on time (dotted line). In the top part these lines can come to an end crosshair which designates a point of heating of a vein of a cable to temperature, limiting on ignition.
5. A line of the maximum value of a current of short circuit. Inconsistency of protection at the currents exceeding maximum, is not checked and it is not considered selectivity infringement.

The analysis of selectivity of protection


The program does not automate process of the coordination of protection, and only informs on a coordination or inconsistency of setpoint. Selection of setpoint is made estimator for final number of operations. In the program the mode is provided “autocalculation” allowing instantly to estimate influence of any adjustment on regime parametres.

Often for reception of the comprehensible decision it is necessary to change initially chosen configuration of a network. Use of computer model allows to make such change with the minimum expenses: time is spent basically for considering and decision-making.

Let's consider documenting of results of calculations in the graphic form.

Results of calculations can be presented and in a graphic kind, and in the form of text tabular documents. The direct conclusion of a graphic representation to the printer or plotter is possible. If the printer has the limited format (A4 or A3) the image can be broken into the set number of sheets and is stuck together after listing. Its scaling both towards increase, and towards reduction is thus possible.

However definitive documents are expedient for forming with use AutoCAD or MS Word. The special tool allows directly from the program or by means of a file of format DXF to transfer the image in AutoCAD (now such transfer can be carried out only for AutoCAD 2004-2005). Format DXF is supported by any version Windows. At any way of transfer the information on colour is broadcast in layers that allows after simple adjustment to receive the colour image of drawing AutoCAD.

In MS Word the scheme image can be transferred by means of the system buffer of an exchange. Thus thanks to internal format WMF (windows metafile) transferred in MS Word the image remains vector and scaled. On quality also I blossom it keeps strict conformity initial in the program and besides occupies a small memory size. If the scheme is entered in a format to A3, and printers support such format is the best decision for the organisation.

Let's consider documenting of results of calculations in the tabular form.

Results in the tabular form can be directly deduced on the printer. However for registration of the total documentation on the basis of calculations it is expedient to take advantage of the external program – for example, MS Word with application of in advance prepared templates. In drawing the example of the cable magazine automatically received in such a way is resulted.

The example of the target document received in an automatic mode on the basis of calculations


Thus, program EnergyCS of the Electrician allows to generate a configuration of a network and to choose necessary structure of the equipment. However it only a part of a design problem. Design questions are not solved. Abstract automatic switches are chosen, but the way of their installation is not considered, the order formula is not defined. The complete equipment, and automatic switches from them trip units is usually used are components of cases or management blocks.

Let's consider constructive designing of switching centers.

Performance of a constructive part of the project of an electrical supply provides ElectriCS ADT. If the switching center type on the basis of the information on a configuration of the network received from program EnergyCS of the Electrician, this system will allow is established:
- to choose necessary types of blocks which correspond to its functional purpose;
- to execute a designation of all elements according to the set rules defined by the standard of the enterprise;
- to create the full set of the design documentation describing made decisions (it can be the task to factory on manufacturing of switching centers and switchboards or the total design documentation in the form of one-linear electric schemes with filling of cells of boards).

The information transfer about a network configuration is carried out by means of the special table of program EnergyCS of the Electrician. This table along with the specific structural information contains data on all results of full complex calculation. The table is transferred in ElectriCS ADT through a file of an exchange of format CSV or XML (further it is planned to provide transfer possibility through the interprogram interface).

Let's consider an apportion of cables.

The apportion of cables on lines of buildings and constructions is made at the final stage of designing of an electrical supply. For its performance are necessary: the description of lines received from 3D-model, the list of final points-consumers and the list actually cables for an apportion. As a rule, on such objects as thermal or nuclear stations, for one operation are displayed on lines not only power cables, but also cables of management information system, communications, alarm systems, etc. Program ElectriCS 3D, intended for the decision of such problems, possesses effective tools for association of lists of the cables being a part of the general computer model and formed in different projecting systems: EnergyCS the Electrician, ElectriCS ADT, AutomatiCS ADT. Besides, ElectriCS 3D has own means of input of the description of the cables received as a result of not automated designing.

Descriptions of cable lines can be presented in a tabular kind or are received directly from the 3D-model of configuration of object prepared in systems PLANT-4D, PDS 3D, Smart Plant 3D, etc. Result of a cable apportion the cable magazine with the description of lines is. In drawing the target document automatically generated on the basis of model is shown.

The example of the target document received in an automatic mode on the basis of calculations


As a result of a cable apportion inevitably increase in lengths of cables. It can lead to increase of losses of pressure and infringement of sensitivity of some protection. Therefore after an apportion of cables carrying out of repeated calculation is necessary. As programs work with computer model performance of verifying calculations is possible. Results of such calculations, naturally, can lead to change of the separate accepted design decisions.

In this article the example of interaction of various programs for reception of the design decisions issued in the form of the design documentation by a power electric part of difficult industrial targets is resulted. At the description of sequence of performance of design procedures presence of projecting systems for other parts of the project co-operating with system of designing of an electric part always is supposed. It is a question not so much of concrete programs, how many about possibility of their use as a part of designing system. Application of the software mentioned in article conducts to essential reductions of expenditures of labour at performance of electrotechnical designing and to improvement of quality of the received decisions.


Sources:
1. Ilyichev N., Salin A., Serov V. Computer-aided design of a distributive network of system of an electrical supply of industrial targets//CADmaster, #4 (29), 2005 [http://csf.ru/file/JRqPFMmXOOFOWfQs8298466/cm_29_proekt_raspr_seti.pdf]
2. Ilyichev N., Serov V. Designing the distribution network of own needs on the basis of computer model with use of program ElectriCA//CADmaster, #1 (21), 2004 [http://csf.ru/file/MkMIpHlvLlmupriL8298467/cm_21_electrica.pdf]

The author: Челябэнергопроект
Date: 07/22/2009

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