Setting up engineering networks. Hydraulic calculations of utility networks as objects of geographic information systems

July 1998

The authors continue the series of articles (see IB GIS No. 1(8), 3(10), 5(12) for 1997) devoted to the use of geoinformation technologies in the operation of utilities. This time we will try to describe the principles of integration of the creation and maintenance subsystems electronic plans engineering communications and hydraulic mode analysis subsystems utility networks. The authors, as in previous articles, consider only municipal networks or networks of large enterprises, and rely on own experience development and implementation of specialized information systems.

Hydraulic calculations underlie the analysis of the regimes of thermal, gas, water supply and pressure sewer networks. In the CIS and Baltic countries, hydraulic calculations are of greatest importance for heating networks, which is determined by the principles of construction and rules of their operation. Any information systems for heating networks that do not provide for hydraulic calculations, have extremely limited opportunities applications and therefore can hardly be considered seriously. Hydraulic calculations of municipal gas, water supply and sewer networks were previously used only by design and scientific organizations. However, recently operating organizations have also shown increasing interest in modeling hydraulic modes.

The needs of the operational services of engineering networks lead to the need to create unified databases, on the basis of which the tasks of creating electronic plans (GIS) are solved top level), and technological problems, in particular - hydraulic calculations of networks. Only this approach to the information content of systems, coupled with methods and algorithms of applied mathematics, allows us to talk about digital model engineering communications as a GIS object.

What is "hydraulic calculation"?

Of course, within the framework of this article, the authors do not intend to provide a strict mathematical formulation of the problem of hydraulic calculation. It is presented in dozens of monographs that have become classics of this field. subject area. You still can’t write better, and therefore we refer those eager for production to the fathers of the modern theory of hydraulic circuits (for example, and). For us, the following is important here: the result of any hydraulic calculation is always flow distribution - for each section of the network there is a flow rate of the transported product, and for each node of the network - pressure. At the same time, the methods for specifying the initial data can differ quite significantly from each other. If the network does not contain regulators (pressure, flow or temperature), then the problem of hydraulic calculation is reduced to a system of high-dimensional nonlinear equations. In turn, the linearization of this system leads to a sparse system of linear equations with a specific structure (cunning mathematicians learned to effectively use the properties of this specific sparseness back in the days of severe restrictions on the computing capabilities of computers). Regulators significantly complicate the task, since in this case inequalities are added to the system of equations.

There are quite a number of methods for solving hydraulic calculation problems, and they are also well known; Thus, the bicycle has been invented, and the problem lies in making it more or less decent. Therefore, the quality of both algorithms and software implementation hydraulic calculation, it is in this field that competitors have been fighting for the third decade. (Without false modesty, we note that the Potok Information Computing Center considers its special pride to be a high-quality hydraulic calculation program, which allows, even on a 386 computer, in 1-2 seconds to obtain complete flow distribution for networks containing thousands of sections, at any degree of their loopiness. The author of this program - our employee, A.L. Podolsky).

Calculation diagram and plan of engineering communications

The first hydraulic calculation programs appeared 30 years ago, long before the advent of mass distribution geographic information systems. Once reliable and efficient hydraulic calculation procedures were established, the challenges of creating user-friendly custom shells began to come to the fore. These shells had to be able to perform the following functions:
initial input of source data;
control of the correctness of the source data;
visualization and analysis of calculation results;
correction of source data.

To obtain the required results, the user had to draw (on paper) a calculation diagram, compile (on paper) tables of sections, consumers, pumping stations and regulators, enter these tables into the computer, obtain calculation tables, apply the calculation results to the calculation diagram (again on paper). At each stage, the user made various errors, the elimination of which took a lot of time and effort. With the advent personal computers Hydraulic calculation systems have undergone revolutionary changes in two directions:
initial and calculated data began to be stored in standard relational databases data, and not in a variety of binary files;
The calculation diagram, now depicted using a computer, has become both the main source of initial data and a means of analyzing calculation results.

Almost simultaneously with the introduction of hydraulic calculation systems with a graphical representation of the design diagram, the possibility of creating and using systems for certification of engineering communications based on electronic plans appears. Since any of these systems is associated with large labor costs for creation and updating Database, problems immediately arose regarding the interaction of these systems. The authors are deeply convinced that the network certification system and the hydraulic mode calculation system are in fact a single information and graphic system, which is based on a database with a carefully thought-out table structure. Utility plans made on the basis of standard city tablets can be used either directly as design diagrams, or converted into design diagrams using automated procedures. Obviously, in order for this to be possible, methods for identifying and systematizing nodes and sections of the network on the plan must be thought out. Especially important issue is a clear definition of network consumers.

Curse of dimensionality

The experience of the authors has shown that real heat, gas and, especially, pressure sewer networks of even large cities do not generate subnetworks with more than 10 thousand sections for which hydraulic calculations are required. Calculation of such networks on modern computers is performed in a matter of seconds, although the processes of reading source information and writing results to the database can take several minutes. This is another argument in favor of the direct use of operational plans as design schemes. Water supply networks of large cities can generate networks containing tens of thousands of sections. For example, the Moscow water supply network contains about 100 thousand sections. Such networks are already difficult to calculate even on supercomputers, but that’s not so bad. Most importantly, with such a dimension it is almost impossible to correctly enter the initial information and then analyze the calculation results. In this case, it is necessary to use semi-heuristic methods for drawing up simplified (equivalent) calculation schemes. (Among the methods that the authors encountered, the most interesting approaches to the selection of design schemes, and indeed to solving problems of hydraulic calculation of water supply networks in general, are used in the State Unitary Enterprise Vodokanal of St. Petersburg). However, information and graphic systems for certification of water supply networks must contain special procedures formation of the initial graphic and text information for constructing calculation schemes.

Methods for visualizing hydraulic calculation results

It is very convenient to present the results of hydraulic calculations using technologies adopted in geographic information systems, although there are also a number of original visualization methods. The main variations are:

Hydraulic certificates about nodes and sections of the network. The user marks the required object on the network diagram and receives help in the window containing the hydraulic and technological characteristics of the node. Types of certificates can be customized according to user requirements.

Generator of reports containing hydraulic modes of units and sections. As a rule, such reports are presented in the form of tables, the rows of which are nodes, sections, consumers or pumping stations, and the columns are technological and hydraulic parameters (flow rates, pressures, speeds, etc.). The list of columns and conditions for selecting objects are customized according to user requirements.

Thematic maps (schemes). Network objects are highlighted using various graphic tools(for example, color) depending on flexible conditions. For example, networks can be colored by pressure zones, highlight hydraulic disturbances, zones of stagnant water, show flow directions with arrows, etc.

Signatures of calculation results on the main network diagram. The user is provided with means of placing special inscriptions associated with utility network objects. The list of displayed parameters is configured according to the user's requirements. These inscriptions are placed in a special layer, which can be turned off at any time so as not to clutter the diagram.

Construction of piezometric graphs. A piezometric graph shows a graph of pressure changes along given path. To construct a piezometric graph, the user marks the necessary nodes on the network diagram, the program automatically finds a path connecting these nodes and generates a special document - a graph containing in a very convenient form necessary information about hydraulic modes (see figure). Along the selected path, arbitrary tables can be generated using the report generator to complement the piezometric graph.

Afterword

The authors hope that in their publications they managed to quietly and unobtrusively lead the respected reader to the main idea about what functionality should be kept in mind when choosing one or another instrumental GIS for building information systems for engineering communications enterprises. And once again they are not lazy to remind you of the relevance of the problem of exchange formats, since it is obvious that it is not the job of “big” municipal GIS to deal with, for example, hydraulic calculations.

See you again!

Literature:

1. Evdokimov A.G., Dubrovsky V.V., Tevyashev A.D., “Flow distribution in engineering networks”, Moscow, Stroyizdat, 1979
2. Merenkov A.P., Khasilev V.Ya., “Theory of hydraulic circuits”, Moscow, Nauka, 1985

JSC Arkada is a leading supplier integrated solutions for automation of industrial enterprises and design organizations, the exclusive representative of the solutions of NTP Truboprovod, invites your specialists to take part in the training program on the topic:

^ Hydraulic and thermohydraulic calculations

V software package"Hydraulic system"

Price: 3,300 UAH.

The event will be conducted by specialists from the development company NTP Truboprovod.

The event is intended for students who perform tasks of performing thermal and hydraulic calculations, as well as selecting the diameters of pipelines pumping liquid or gaseous products, as well as gas-liquid mixtures.

Day 1.

^ Functions and main capabilities of the “Hydraulic System” program. Theoretical basis hydraulic and thermal calculations of pipelines.

Capabilities of the “Hydraulic System” program and limitations of its scope.
The structure of the “Hydraulic System” program and the purpose of its modules.
Statement and formalization of the tasks solved in the program:

Design calculation, calculation bandwidth, verification calculation:
Flow, pressure and pipe diameters in pipelines, their relationship. Pressure drop in pipelines, Bernoulli equation.
Flow modes – laminar, turbulent, transitional. Reynolds number. The dependence of pressure drop on speed is linear and quadratic.
Roughness of pipes and calculation of pressure losses in pipes. Selecting the roughness value.
Local resistances and their calculation (reference books by Idelchik, Miller).

Thermal calculation of pipelines. Calculation of heat losses to the environment. Shukhov's formula. The main thermal resistances of the heat transfer process from the pumped product to the environment. Taking into account the properties of real gas (throttle effect), taking into account friction energy for liquids.
Calculation of two-phase flow. Basic approaches to modeling two-phase flows, basic dependencies and correlations for calculating true gas content, two-phase resistances, flow regimes of a two-phase mixture.
The phenomenon of cavitation. Cavitation reserve and its calculation.

User interface of the “Hydraulic System” program, specifying initial data.

Basic concepts of the design scheme. Hydraulic resistance, section, branch, node, source, consumer.
Review of windows, menus and panels of the program, customizing the interface.
The structure of the source data and their assignment:

Setting general data for the pipeline.
Data on environment and thermal insulation structure (working with a database of insulating materials).
Specifying product data. Methods of assignment and their features. Modeling of oils and oil products, recalculation of distillation of oil fractions.
Specifying pipeline branches and data on them. Flow direction in branches, inflows/outflows at branch nodes.
Types of sections (hydraulic resistance) and their use, modeling of “lumped” resistance and resistance having a length. Input and accounting of tees. Pump assignment.
Inserting nodes into a pipeline, defining closed contours, defining closed pipeline fittings.
Graphic display calculation scheme and its settings. Accurate graphics mode, synchronization of data on elements with their graphic display.

Day 2.

Performing calculations in the “Hydraulic System” program. Practical lesson.

Schematization real design pipeline and right choice calculation scheme. The importance and correctness of taking into account certain elements of the scheme.
Statement of the problem to be solved in the program, specified and sought values.
Types of calculations performed by the program, their purpose and practical use:

Design calculation: taking into account restrictions on the speed of product movement, design calculation settings. Performing calculations yourself.
Calculation of throughput and flow distribution in the pipeline. Setting control valves. Performing calculations yourself.
Verification hydraulic and thermal calculations: calculations “from source to consumer” and vice versa, various variations of calculations. Performing calculations yourself.
Calculation of two-phase flow: types of two-phase flows (“frozen” flow and flow with boiling/condensation), features of calculation settings. Performing calculations yourself.

Presentation and printing of calculation results.
Engineering interpretation of calculation results.

GeoInfoGrad conducts distance learning the use of GIS Zulu and ZuluThermo for electronic cartography, modeling, adjustment of heating networks, development and updating of electronic models of systems and heat supply diagrams.

ZuluThermo training course

Example of educational videos

Introductory lecture

« Electronic model heating systems and modern approach to the adjustment and modernization of heating networks with an example"

within the framework of the program “FUNDAMENTALS FOR THE DEVELOPMENT OF HEAT SUPPLY SCHEMES FOR SETTLEMENTS AND URBAN DISTRICTS” to improve the qualifications of government officials local government and specialists from heat supply organizations conducted by the Federal State Autonomous Educational Institution of Further Professional Education "IPK TEK"

Practical lessons

1. Basic user interface elements and operations:
a. Menu, toolbar, moving around the map, zooming.
b. Setting the scale and coordinates.
c. Navigator, workplace, list of maps and layers.
d. Turning on/off the visibility of layers, arrangement order. Types of layers: vector, raster, calculation. Active layer.

2. Basic tools. Selecting an object, group, objects. Geometric properties of an object.

3. Measuring distances and areas.

Lesson 2. Introduction 2 0:25

ZuluThermo training course. Video materials. Table of contents. Practical lessons

Lesson 1. Part 1. Introduction 0:13

Basic user interface elements and operations:

Menu, toolbar, moving around the map, zooming.
Setting the scale and coordinates.
Navigator, workspace, list of maps and layers.
Turning on/off the visibility of layers, arrangement order. Types of layers: vector, raster, calculation. Active layer.

Basic tools. Selecting an object, group, objects. Geometric properties of an object.
Measuring distances and areas.

Lesson 1. Part 1. Data on objects 0:09

Data for the selected object. Data for all objects of the type. Requests.

Lesson 1. Part 2. Working with the existing calculation model of the heat supply system 1:31

Editing existing map. Adding new consumers and network sections.
Coloring by speed. Piezometric graph. Checking the topological connectivity of the network.
Review of data on network elements. Filling in the initial data for calculations for added network elements. Calculation with an added consumer. Calculation analysis. Selecting the appropriate diameter.

Lesson 1. Part 3. Working with the existing calculation model of the heat supply system 0:39

Editing an existing map. Adding new consumers and network sections (continued).
Analysis of independent work.
Export data to Excel.
Printing without layout. Print on multiple pages.

Lesson 2. Introduction2 0:25

Creation of a computational layer and calculation of a small network. Short review main features of ZuluThermo: Input of initial data, calculation, analysis of calculation results, recommendations for improving the hydraulic mode.

Lesson 2. Part 1 1:40

Database creation,
Export from AutoCAD
Connecting rasters. Calibration Grouping
Layer Transformation

Lesson 2. Part 2 1:02

Connecting rasters public cards and space images (continued),
Creating layers (repetition). Drawing.
Filling out table data, automatically filling in section lengths.
Arranging and editing inscriptions.

Lesson 3. Part 1. Calculation of the heating network 0:57

Calculation settings.
Filling in the initial data for calculation.
Calculation. Review of calculation results.
Modeling of a 4-pipe network with hot water supply.

Lesson 3. Part 2 1:10

Verification calculation of the heating network.
Temperature chart.
Calculations taking into account heat losses.
Types and modes of elements of the heat supply system/calculation layer:
1. network operation with a pumping station,
2. valve,
3. generalized consumer
4. throttling unit,
5. jumper.
Help on network elements and their parameters

Lesson 4. Part 1 1:01

Layer structure. Styles Types and modes. Legend, scaling symbols. Editing, creating new ones. Primitive and standard objects.
Layer databases. Editing database tables. Adding a field to a table. Data types. Requests. Design of a user table (query). Grouping and coloring fields. Using documents, files, images as data.

Lesson 4. Part 2 1:19

Demo Mode Limitations
Data structure (continued). Creating a table in a new layer. Requests (example).
Layer properties. Generalization - range of visibility scales.
Project.
Seal. Print layout.
Rasters. Insert. Adjust transparency and color.

Lesson 5 2:08

Inserting, snapping, calibrating rasters
“Service” tab in the ZuluThermo module: Elevation marks from the map, relief. Automatic filling lengths, ends of the site from the map.
Calculation of standard heat losses.
Coloring the heating network in 2 ways. Thematic coloring pages. Show diameter by thickness, loss by color.
Overlay operations. Addition, subtraction of objects.
Selecting groups of objects. Mass operations with groups.
Removing unnecessary and adding empty records in the database.
Working with database tables.
Searching for an object by key.
Transforming a layer from the screen and parameters.
Copying, renaming, indexing a layer.

Teachers: Lunyakov A.V., Govorov V.L.

The convenience of using GIS as an information and reference system with utility networks, streets and houses accurately mapped to the area is obvious. GIS allows you to link network objects to the territory, connect attribute information to them, perform visualization, spatial analysis and queries, print information, etc.

However, during the operation of utility networks, many specific questions arise that are not directly related to GIS: what pressure will be in the pipeline if the pump fails, how many consumers will be without water when the valve is turned off, what will be the short circuit current on the bus. If you cannot quickly and correctly answer dozens of similar questions, then it is difficult to talk about the possibility of effective network management. Networks need to be able to count.

A little theory

The basis of the mathematical model for network calculations is a graph. As you know, a graph consists of nodes connected by arcs.

Any network can have its own set of node elements. For example, in heat supply these are sources, thermal chambers, consumers, pumping stations, shut-off valves; in power supply - sources, transformers, consumers, switches, etc.

The arcs of the graph are sections of the network: pipelines, cables. The section must begin at some node and end with a node (Fig. 1).

Rice. 1. An example of a fragment of a heating network received from surveyors.

Sections of pipelines running between the concrete walls of the canals end at the walls of buildings and the walls of wells. It is obvious that it is impossible to directly use this information to build a computational mathematical model. From the point of view of the model, this is nothing more than a drawing.

And it is not surprising that for a long time, at enterprises operating networks, there could be completely independent services involved in maintaining diagrams, drawings, linking network objects to the territory, network certification, and departments involved in technological calculations of networks. IN software , not using geographic information technologies , description network graph (network coding) was carried out in tabular form. For example, shown in Fig. 1 fragment of the graph, consisting of three consumers and four thermal chambers, could be represented in tabular form

(see Fig. 2). Rice. 2.

A fragment of the graph in tabular form.

Let's check whether we have described all sections of the network fragment. Looking through the entries in the table and comparing them with the figure, it is easy to notice that we have missed one section (TK3, TK2). You can quickly add a record to the table and correct the error.

It seems that everything is not so complicated, but there can be thousands of such sites in the network. It’s easy to understand that it won’t be long before you start doing calculations and analyzing their results (for which, in fact, coding is needed). And even after finishing coding the network, a conscientious specialist will periodically be tormented by the thought of whether he entered everything correctly. Now let's imagine that there is graphics editor

, which allows you to work with points and lines endowed with a number of additional properties not related to coordinate reference and display style:
A point object is also a node in a mathematical graph.

If the graphic editor allows you to add objects with such properties, then when starting to draw a section of the network, you will need to either bind the beginning of the section to one of the existing nodes, or select from the set of nodes included in the layer structure the node at which this section will begin. In the same way, when finishing entering a section, you need to either tie its end to one of the existing nodes, or install a new node at which the section will be completed.

If we move a node (change its coordinates), then the beginnings and ends of the sections associated with this node will move along with it.

That is, changing the position of nodes in space will not lead to a change in the topology of the graph. The network will not “fall apart”. From the point of view of the mathematical model, it is completely unimportant whether the coordinates of nodes and breaking points of sections will be entered according to coordinates with geodetic accuracy, outlined on some kind of substrate, or simply depicted schematically. Important, that the right pairs

nodes are connected by arcs, and as a result of “drawing” the network, we automatically obtain the encoding of the mathematical graph of the network. If the drawing is done correctly, then the network graph will not contain errors. Now let’s imagine that a geographic information system has such a topological editor. Then all the capabilities and advantages of GIS are combined with the ability to describe in graphical form

mathematical model of the network. When a GIS has the described properties, it is customary to say that it supports line-node topology. Rice. 3.

A section of a network in the form of a graph.

Returning to the above example and using it to represent the network as a graph, you can get a fragment of the layer for calculations (Fig. 3). This layer contains information about the spatial position of network elements and the mathematical model of the network.

Thus, we can talk not about editing polylines or points - geometric primitives, but about editing meaningfully defined objects - consumers, conductors, switches, transformers or pipelines, valves, pumps.

Topological problems

In engineering networks, regardless of their purpose, a number of common elements, from a topological point of view, can be identified.

1. Source. Nodal element. In electricity supply, this can be a voltage source, a transformer substation, in water supply - a water tower, a well, in heat supply - a boiler room, a thermal power plant.

A source can have two states: enabled or disabled.

2. Consumer. Nodal element. These are consumers of water, gas, electricity and heat. A source can have two states: connected or disconnected.

3. Cut-off device. Nodal element. In the power supply these are switches, switches, contactors, in pipeline networks - shut-off valves: valves, gate valves, taps. The shut-off device can have two states: open or closed.

4. Simple nodes are used to connect sections and always have one state - open.

5. Site. Linear object. Connects a pair of nodes. These are cables, power lines, pipeline sections. Depending on the specific implementation, a section can also have states: open or closed. In addition, the section has a direction from the start node to the end node.

There can be many specific tasks that use the topological properties of a network graph. Let's list some of them.

Connectivity check. This check is based on finding a path through a graph between two nodes. If a path between nodes is found, then the nodes are connected to each other and are members of the same subnet.

Search for nearby cut-off devices. This capability is extremely important when localizing the site of an accident or when planning to shut down sections of the network from operation. Network configurations can be quite complex, and it is difficult to mentally and quickly determine which cut-off devices need to be closed to isolate a section of the network. Mistakes in such cases can be very costly. It is especially important that the shutdown is optimal, that is, it leads to the shutdown of a minimum number of consumers.

Such problems can be solved very simply on a network graph.

Analysis of the results of switching in the network. Let's consider two states of a network fragment, before and after turning off the valve (Fig. 4). Rice. 4.

Two states of a network fragment: before and after turning off the valve.

When the valve on the map is switched to the “closed” state, the network graph is recalculated, and consumers cut off from the source automatically assume the “disconnected” state. At the same time, a list of disconnected consumers is formed. If there is a layer with buildings on the map, and consumer nodes are placed inside the outlines of buildings, then using a spatial query you can determine which buildings have been disabled and get a list of their addresses.

The results of the disconnection can be transferred to the dispatch system to generate entries in the disconnection log, and the list of disconnected subscribers can be transferred to the system for settlements with consumers to recalculate the charged subscription fee.

Note that when tens or hundreds of consumers are disconnected, obtaining such lists “manually” is quite labor-intensive and is not guaranteed against errors.

Technological calculations

Knowing the network topology allows you to find answers to many questions.

But there are a number of problems that cannot be solved without taking into account the physical essence of networks. Let's consider an example of a simple heating network diagram with two sources and two consumers (Fig. 5).

Rice. 5. Diagram of a heating network with two sources and two consumers. How to determine which direction the water will flow in the middle section?

For each type of engineering networks, there are many methods for their technological calculations. These are electrical, hydraulic, thermal-hydraulic, strength calculations. It is important to note that the use of GIS greatly facilitates and simplifies the work of creating a computational network model and entering attribute data.

Calculation model and reality

It should be noted that the network created for calculations is still a model, and not a complete copy of the network on the ground. They have a number of differences.

1. Single-line representation of sections. In some networks, sections contain several parallel threads. So, in electric three-phase network There are three phases in parallel, or three phases and zero. In heating networks, as a rule, there are always supply and return pipelines nearby, and there can be three-pipe and four-pipe networks. From the point of view of the model, there is no need to draw three wires or two pipes next to each other. The user enters sections of the network into one line, and the calculation task, if necessary, itself converts the external representation of the network into internal encoding. For example, the circuit shown above will be converted in computer memory to approximately the form shown in Fig. 6.

Rice. 6. An example of a single line representation.

2. Degree of detail when depicting the network. It may vary depending on the requirements of the model. For example, there may be hundreds of valves in a water supply network. Their purpose is to block certain sections of the network. But the model can be built in such a way that there is no need to depict valves. Instead of a valve, you can simply “turn on” and “turn off” the section itself, and the physical influence of the valve can be taken into account in the attributes by the coefficient of local resistance (Fig. 7).

Rice. 7. Equivalent circuits, the second circuit is simplified.

The circuits shown in the figure are equivalent, but the second circuit has three nodes and three sections less. When there are thousands of such “extra” objects and you need to enter dozens of attributes on them, the input time increases significantly.

If there are several subscriber nodes in the building, then the “consumer” object can describe each input node separately. And in the same network, an entire block can be described by one generalized consumer (Fig. 8).

Rice. 8. Full (top) and simplified diagrams of the “consumer” representation.

In the life of a consumer, there is no such thing as a block. But it is precisely this generalization that allows you to quickly calculate backbone networks without drawing distribution network inside the block. This is especially important when backbone and intra-block networks are on the balance sheet of different enterprises.

3. Accuracy and detail of the image. The geodetic accuracy of specifying coordinates and the mandatory presence of all turning points in sections in some calculation problems do not have of great importance. For example, turns and bends of a conductor do not in any way affect the strength of the current flowing in it. What is important is the total length of the wire, which can be set as an attribute. That is, on the one hand, it is very convenient when the calculated network graph is tied to the area, but, on the other hand, entering a simplified network diagram allows engineers to quickly start calculations. Therefore, in many organizations the network diagram for certification and technology system

for calculations are carried out in parallel, although the problem of reconciling several representations of the same network arises.

Entering attribute information

Compared to depicting a design network on a map, assigning attributes to network features can take much longer. For some objects, the number of attributes, depending on the tasks being solved, can be several dozen. The simplest way is to sequentially indicate each object and enter information about it. Graphical representation of data helps speed up this process.

If you select groups of objects with the same attributes on the map, then attributes can be assigned to the entire group at once. If the map is drawn to scale and the network is entered with good accuracy, then the lengths of network sections for calculations can be obtained from the graphical database. If there is a layer with terrain, geodetic marks of nodes can also be obtained automatically. If, to calculate the heat losses of pipelines with underground installation, information about the type of soil is required, and there is a contour layer for soils, then the soil type can be assigned to all sections at once by running just one spatial query. GIS can also be of great help in ensuring that the attributes entered are correct. For example, in ArcGIS it is possible to preset valid values attributes either in range view , or as a list of values. When entering data, the operator selects one of the values for of this type or subtype of objects, while the likelihood of error is greatly reduced. Additionally, after finishing your editing session, you can run special check

There are many ways to simplify attribute entry and error control, and you can add own ways, which depend on specific tasks and user ingenuity.

Analysis of calculation results

The process of entering the computational network topology and its attribute data can be difficult and time-consuming, but most of the work is done only once. Calculations are usually performed many times, and the efficiency of using the calculations themselves largely depends on the convenience of analyzing the results.

The results of calculations, regardless of their purpose, are recorded in tables. For example, in power supply these are voltages at all nodes, current strength and losses at each section; in heat supply - pressures and temperatures in each node, costs, speeds and losses in each section.

In tabular form, going through thousands of records and identifying incorrect results caused by errors in the source data can be quite inconvenient.

The use of GIS provides traditional analysis of tables: queries, sorting, selection. In addition, the user receives a powerful tool for visualizing results and performing spatial queries. It is very convenient to move through the entries in the table and immediately display on the map the object corresponding to the current entry. Using the mechanism for creating thematic maps, you can color sections of the network according to various criteria: by the amount of losses, by the speed of water movement, by temperature, by affiliation with the source. Highlighting by color according to certain parameters allows you to immediately see critical places in the network and evaluate

quality level

adequacy of certain results.

One of the main documents created based on the results of hydraulic calculations for all pipeline networks is a piezometric graph. It depicts a line of pressure change in network nodes along some route selected on the network graph, for example, from a source to one of the consumers. Using GIS to build a route, it is enough to indicate its starting and ending nodes. After this, the route is built automatically. If there can be several paths from node to node, then it is enough to specify a number of intermediate nodes. After constructing a graph that can pass through hundreds of nodes, it is convenient to organize the interaction of the graph with the map: having indicated a point on the graph, immediately show on the map the node to which this point corresponds.

Extremely useful is the ability to display graphical information, source data and calculation results together. Using GIS, you can easily label objects, indicating which attribute fields need to be displayed on the map (Fig. 9).

Engineering calculations for ArcGIS 8

The St. Petersburg company Polytherm has developed calculation modules for heat and water supply systems. Our software and calculation complex "ARMTEST-Zulu" has been used for many years in many cities of Russia. And now the first version of calculations for ArcGIS 8 has been released - the Zulu ArcHydro and Zulu ArcThermo modules.

To build a computational network model, a topological editor running under ArcEditor and ArcInfo is used. The developed applications allow the user to independently create a new computational network, edit its topology, enter attribute information on network objects and perform technological calculations.

Verification calculation of the water supply network

The purpose of the verification calculation is to determine the flow distribution in the water supply network, the supply and pressure of sources with known pipe diameters and water withdrawals at nodal points.

To perform a verification calculation, the following values are used as initial values:

Diameters and lengths of all sections of the network and, therefore, their hydraulic resistance
Fixed nodal water withdrawals
Pressure and flow characteristics of all sources
Geodetic marks of all nodal points

As a result of the verification calculation, the following are determined:

Costs and pressure losses in all sections of the network
Feeding sources
Piezometric pressures in all system nodes.

Verification calculations include calculations of the system in case of extinguishing a fire at the hour of greatest water consumption, and calculations of the network and water pipelines with an acceptable reduction in water supply due to accidents in certain areas. These calculations are necessary to assess the performance of the system under conditions other than normal, to identify the possibility of using the designed pumping equipment in these cases, as well as to develop measures to prevent a drop in free pressures and a decrease in supply below the limit values.

Design calculation of the water supply network

The purpose of the design calculation of a dead-end and ring water supply network is to determine the diameters of pipelines that ensure the passage of calculated water flows at a given pressure.

The design operating mode of the network is understood as such possible combinations of water extraction and its supply by pumping stations, under which the greatest loads occur for individual structures of the system, in particular the water supply network. Loads include water flow rates and pressures.

The water supply network, like other utilities, must be calculated in the interconnection of all structures of the water supply and distribution system.

The calculation of the water supply network is carried out with any set of objects, characterizing the water supply system, including those with several sources.

Adjustment calculation of the heating network

The purpose of the adjustment calculation is to provide consumers with the calculated amount of water and thermal energy. As a result of the calculation, elevators and their nozzles are selected, mixing and throttling devices are calculated, and the number and location of installation of throttle washers is determined. The calculation can be made with a known available pressure at the source or with it automatic selection in case the specified pressure is not enough.

Throttling of excess pressure at subscriber inputs is carried out using elevator nozzles and throttling washers. Throttle washers in front of customer inputs are automatically placed on the supply, return or both pipelines, depending on the hydraulic mode required for the system. When several sources operate on one network, the distribution of water and thermal energy between the sources is determined. A balance is established for water and supplied thermal energy between the source and consumers. Consumers and their corresponding source are determined, from which these consumers receive water and heat energy.

Verification calculation of the heating network

The purpose of the verification calculation is to determine the actual coolant flow rates in sections of the heating network and at consumers, as well as the amount of thermal energy received by the consumer at a given water temperature in the supply pipeline and available pressure at the source.

Created mathematical simulation model The heat supply system, which serves to solve the verification problem, allows one to analyze the hydraulic and thermal operating conditions of the system, as well as predict changes in the internal air temperature of consumers. Calculations can be carried out with various initial data, including emergency situations, for example, when disconnecting individual areas heating network, transfer of water and thermal energy from one source to another through one of the pipelines, etc.

As a result of the calculation, costs and pressure losses in pipelines, pressures at network nodes, including available pressures at consumers, coolant temperature at network nodes (taking into account heat losses), internal air temperatures at consumers, costs and water temperatures at inlet and outlet are determined into each heat consumption system. When several sources operate on one network, the distribution of water and thermal energy between the sources is determined. A balance is established for water and supplied thermal energy between the source and consumers. Consumers and their corresponding source are determined, from which these consumers receive water and heat energy.

Design calculation of the heating network

The purpose of the design calculation is to determine the diameters of the pipelines of a dead-end and ring heating network when the calculated flow rates are passed through them at a given (or unknown) available pressure at the source.

This task can be used when issuing permission to connect consumers to the heating network, since any node of the heat supply system, for example a thermal chamber, can act as a source. For more flexible solution

This task provides for the possibility of changing the speed of water movement along sections of the heating network, which leads to a change in the diameters of the pipeline, and therefore the available pressure at the connection point.