ON THE. Popov
SYSTEM AUTOMATION
HEAT AND GAS SUPPLY
AND VENTILATION
Novosibirsk 2007
NOVOSIBIRSK STATE
ARCHITECTURAL AND CONSTRUCTION UNIVERSITY (SIBSTRIN)
ON THE. Popov
SYSTEM AUTOMATION
HEAT AND GAS SUPPLY
AND VENTILATION
Tutorial
Novosibirsk 2007
ON THE. Popov
Automation of heat and gas supply and ventilation systems
Tutorial. - Novosibirsk: NGASU (Sibstrin), 2007.
ISBN
The training manual discusses the principles of developing automation schemes and existing engineering solutions for automating specific heat and gas supply and heat consumption systems, boiler plants, ventilation systems and microclimate conditioning systems.
The manual is intended for students studying in the specialty 270109 direction "Construction".
Reviewers:
– P.T. Ponamarev, Ph.D. Associate Professor of the Department
Electrical Engineering and Electrotechnologies SGUPS
– D.V. Zedgenizov, Ph.D., senior researcher laboratory of mine aerodynamics of the Institute of Mining Mining SB RAS
© Popov N.A. 2007
| TABLE OF CONTENTS | |
| FROM . |
|
| Introduction ................................................ ................................ | 6 |
| 1. Fundamentals of designing automated systems heat and gas supply and ventilation……………………… | 8 |
| 1.1. Design stages and composition of the system design process automation ........................................ | 8 |
| 1.2. Initial data for design ........................................ | 9 |
| 1.3. Purpose and content of the functional diagram ........ | 10 |
| 2. Automation of heat supply systems............................... | 14 |
| 2.1. Tasks and principles of automation............................................... | 14 |
| 2.2. Automation of make-up devices of CHP plants .................................. | 15 |
| 2.3. Automation of heating deaerators……… | 17 |
| 2.4. Automation of main and peak heaters… | 20 |
| 2.5. Automation of pumping substations .......................................... | 25 |
| 3. Automation of heat consumption systems .............................. | 33 |
| 3.1. General remarks………………...................................... | 33 |
| 3.2. Automation of central heating stations……………..................................….. | 34 |
| 3.3. Automatic control of hydraulic modes and protection of heat consumption systems……………….. | 43 |
| 4. Automation of boiler plants…………………… | 47 |
| 4.1. Basic principles of automation of boiler houses……… | 47 |
| 4.2. Automation of steam boilers………………………… | 48 |
| 4.3. Automation of hot water boilers…………………… | 57 |
| 5. Automation of ventilation systems………………… | 65 |
| 5.1. Automation of supply chambers………………………. | 65 |
| 5.2. Automation of aspiration systems……………………… | 72 |
| 5.3. Automation of exhaust ventilation systems….. | 77 |
| 5.4. Automation air curtains……………… | 79 |
| 6. Automation of air conditioning systems…… | 82 |
| 6.1. Basic provisions……………………………………. | 82 |
| 6.2. Automation of central air conditioning systems……………………… | 83 |
| 7. Automation of gas supply systems……………………. | 91 |
| 7.1. City gas networks and modes of their operation…………. | 91 |
| 7.2. GDS Automation……………………………………… | 92 |
| 7.3. Hydraulic fracturing automation………………………………………… | 95 |
| 7.4. Automation of gas-using installations…………. | 97 |
| Bibliography……………………………………………. | 101 |
INTRODUCTION
Modern industrial and public buildings are equipped with complex engineering systems to ensure the microclimate, household and production needs. Reliable and trouble-free operation of these systems cannot be ensured without their automation.
Automation tasks are solved most effectively when they are worked out in the process of developing a technological process.
Creation effective systems Automation predetermines the need for a deep study of the technological process not only by designers, but also by specialists from installation, commissioning and operating organizations.
At present, the state of the art makes it possible to automate almost any technological process. The expediency of automation is solved by finding the most rational technical solution and determining economic efficiency. At rational application contemporary technical means automation increases labor productivity, reduces the cost of production, increases its quality, improves working conditions and raises the culture of production.
Automation of TG&V systems includes issues of control and regulation of technological parameters, control of electric drives of units, installations and actuators (IM), as well as issues of protection of systems and equipment in emergency modes.
The tutorial covers the basics of automation design technological processes, automation schemes and existing engineering solutions for automation of TG&V systems using materials standard projects and individual developments of design organizations. Much attention is paid to the choice of modern technical means of automation for specific systems.
The textbook includes materials on the second part of the course "Automation and control of TG&V systems" and is intended for students studying in the specialty 270109 "Heat and gas supply and ventilation". It can be useful for teachers, graduate students and engineers involved in the operation, regulation and automation of TG&V systems.
1. DESIGN BASICS
AUTOMATED SYSTEMS
HEAT AND GAS SUPPLY AND VENTILATION
Design stages and scope of the project
When developing project documentation for the automation of technological processes of objects, they are guided by building codes (SN) and building codes and regulations (SNiP), departmental building codes (VSN), state and industry standards.
In accordance with SNIP 1.02.01-85, the design of technological process automation systems is carried out in two stages: a project and working documentation or in one stage: a working draft.
The following main documentation is being developed in the project: I) a block diagram of management and control (for complex systems management); 2) functional diagrams of automation of technological processes; 3) plans for the location of shields, consoles, tools computer science etc.; 4) application lists of devices and means of automation; 5) technical requirements for the development of non-standardized equipment; 6) explanatory note; 7) assignment to the general designer (adjacent organizations or the customer) for developments related to the automation of the facility.
At the stage of working documentation, the following are developed: 1) a block diagram of management and control; 2) functional diagrams of automation of technological processes; 3) basic electrical, hydraulic and pneumatic circuits for control, automatic regulation, control, signaling and power supply; I) general types of boards and consoles; five) wiring diagrams shields and consoles; 6) diagrams of external electrical and pipe wiring; 7) explanatory note; 8) custom-made specifications for instruments and automation equipment, computer equipment, electrical equipment, switchboards, consoles, etc.
In a two-stage design, structural and functional diagrams at the stage of working documentation are developed taking into account changes in the technological part or automation decisions made during the approval of the project. In the absence of such changes, the said drawings are included in the working documentation without revision.
In the working documentation, it is advisable to give calculations of regulating throttle bodies, as well as calculations for the choice of regulators and determining the approximate values of their settings for various technological modes of operation of the equipment.
The working draft for one-stage design includes: a) technical documentation developed as part of the working documentation for two-stage design; b) local estimate for equipment and installation; c) assignment to the general designer (adjacent organizations or the customer) for work related to the automation of the facility.
1.2. Initial data for design
The initial data for the design are contained in the terms of reference for the development of the system automatic control technological process. The terms of reference are drawn up by the customer with the participation of a specialized organization entrusted with the development of the project.
The assignment for the design of an automation system contains the technical requirements for it by the customer. In addition, a set of materials necessary for design is attached to it.
The main elements of the task are the list of automation objects of technological units and installations, as well as the functions performed by the control and regulation system that ensures the automation of the management of these objects. The task contains a number of data that define the general requirements and characteristics of the system, as well as describing the objects of control: 1) the basis for the design; 2) operating conditions of the system; 3) description of the technological process.
The basis for the design contains links to planning documents that determine the procedure for designing an automated process, planned design dates, design stages, allowable level the cost of creating a control system, a feasibility study for the feasibility of designing automation and assessing the readiness of an object for automation.
The description of the operating conditions of the designed system contains the conditions for the flow of the technological process (for example, the explosion and fire hazard class of the premises, the presence of aggressive, wet, damp, dusty environment etc.), requirements for the degree of centralization of control and management, for the choice of control modes, for the unification of automation equipment, conditions for repair and maintenance of the fleet of devices at the enterprise.
The description of the technological process includes: a) technological schemes of the process; b) drawings industrial premises with accommodation technological equipment; c) drawings of technological equipment indicating design units for installing control sensors; d) power supply schemes; e) air supply schemes; f) data for the calculation of control and regulation systems; g) data for calculating the technical and economic efficiency of automation systems.
1.3. Purpose and content of the functional diagram
Functional diagrams (automation diagrams) are the main technical document that defines the functional block structure of individual nodes for automatic control, management and regulation of the technological process and equipping the control object with devices and automation equipment.
Functional diagrams of automation serve source material for the development of all other documents of the automation project and establish:
a) the optimal amount of automation of the technological process; b) technological parameters subject to automatic control, regulation, signaling and blocking; c) the main technical means of automation; d) placement of automation equipment - local devices, selective devices, equipment on local and central panels and consoles, control rooms, etc.; e) the relationship between automation tools.
On the functional diagrams communication automation and liquid and gas pipelines are depicted by symbols in accordance with GOST 2.784-70, and pipeline parts, fittings, heat engineering and sanitary devices and equipment - in accordance with GOST 2.785-70.
Devices, automation equipment, electrical devices and elements of computer technology on functional diagrams are shown in accordance with GOST 21.404-85. In the standard, primary and secondary converters, regulators, electrical equipment are shown with circles with a diameter of 10 mm, actuators - with circles with a diameter of 5 mm. The circle is separated by a horizontal line when depicting devices installed on boards, consoles. In its upper part, the measured or controlled value and the functional characteristics of the device (indication, registration, regulation, etc.) are written with a conditional code, in the lower part - the position number according to the scheme.
The most commonly used designations of measured quantities in TGV systems are: D- density; E- any electrical quantity; F- expense; H- manual impact; TO- time, program; L- level; M- humidity; R- pressure (vacuum); Q- quality, composition, concentration of the medium; S- speed, frequency; T- temperature; W- weight.
Additional letters clarifying the designations of the measured quantities: D- difference, difference; F- ratio; J- automatic switching, running around; Q- integration, summation over time.
Functions performed by the device: a) information display: BUT-signalization; I- indication; R- registration; b) formation of a profitable signal: FROM- regulation; S- enabling, disabling, switching, signaling ( H And L are the upper and lower limits of the parameters, respectively).
Additional letter designations reflecting the functional features of the devices: E- sensitive element (primary transformation); T- remote transmission (intermediate conversion); TO- control station. Type of signal: E- electric; R- pneumatic; G- hydraulic.
The symbol of the device should reflect those features that are used in the circuit. For example, PD1- a device for measuring differential pressure, indicating a differential pressure gauge, RIS- a device for measuring pressure (vacuum), showing with a contact device ( electrocontact pressure gauge, vacuum gauge), LCS-electric contact level regulator, TS- thermostat, THOSE- temperature sensor, FQ1- a device for measuring flow (diaphragm, nozzle, etc.)
An example of a functional diagram (see Fig. 1.1),
Rice. 1. 1. An example of a functional diagram
reduction-cooling plant automation
where the technological equipment is shown in the upper part of the drawing, and below in the rectangles are the devices installed locally and on the operator's board (automation). On the functional diagram, all devices and automation equipment have letter and number designations.
The contours of technological equipment on functional diagrams are recommended to be made with lines 0.6-1.5 mm thick; pipeline communications 0.6-1.5 mm; devices and means of automation 0.5-0.6 mm; communication lines 0.2-0.3 mm.
Automation of heat and gas supply and ventilation processes
1. Microclimate systems as automation objects
Maintaining the specified microclimate parameters in buildings and structures is ensured by a complex of engineering systems for heat and gas supply and microclimate conditioning. This complex produces thermal energy, transports hot water, steam and gas through heat and gas networks to buildings and the use of these energy carriers for industrial and economic needs, as well as to maintain the specified microclimate parameters in them.
The system of heat and gas supply and microclimate conditioning includes external systems of centralized heat supply and gas supply, as well as internal (located inside the building) engineering systems for providing microclimate, household and production needs.
The district heating system includes heat generators (CHP, boiler houses) and heating networks through which heat is supplied to consumers (heating, ventilation, air conditioning and hot water supply systems).
The centralized gas supply system includes gas networks of high, medium and low pressure, gas distribution stations (GDS), gas control points (GRP) and installations (GRU). It is designed to supply gas to heat generating installations, as well as residential, public and industrial buildings.
The microclimate conditioning system (MCS) is a set of tools that serve to maintain the specified microclimate parameters in the premises of buildings. SCM includes heating systems (SV), ventilation (SV), air conditioning (SV).
The mode of heat and gas supply is different for different consumers. So the heat consumption for heating depends mainly on the parameters of the outdoor climate, and the heat consumption for hot water supply is determined by the water consumption, which varies during the day and on the days of the week. Heat consumption for ventilation and air conditioning depends both on the mode of operation of consumers and on the parameters of the outside air. Gas consumption varies by month of the year, day of the week and hour of the day.
Reliable and economical supply of heat and gas to various categories of consumers is achieved by using several stages of control and regulation. Centralized control of heat supply is carried out at the CHPP or in the boiler house. However, it cannot provide the necessary hydraulic and thermal conditions for numerous heat consumers. Therefore, intermediate steps are used to maintain the temperature and pressure of the coolant at central heating points (CHP).
The operation of gas supply systems is controlled by maintaining a constant pressure in certain parts of the network, regardless of gas consumption. The required pressure in the network is provided by gas reduction in the GDS, GRP, GRU. In addition, the gas distribution station and hydraulic fracturing have devices to turn off the gas supply in case of an unacceptable increase or decrease in pressure in the network.
Heating, ventilation and air conditioning systems carry out regulatory actions on the microclimate in order to bring its internal parameters in line with the normalized values. Maintaining the temperature of the internal air within the specified limits for heating period is provided by the heating system and is achieved by changing the amount of heat transferred to the room by heating devices. Ventilation systems are designed to maintain acceptable values of microclimate parameters in the room based on comfortable or technological requirements for indoor air parameters. Regulation of the operation of ventilation systems is carried out by changing the flow rates of supply and exhaust air. Air conditioning systems ensure the maintenance of optimal microclimate parameters in the room based on comfort or technological requirements.
Hot water supply systems (DHW) provide consumers with hot water for household and economic needs. The task of DHW control is to maintain a given water temperature at the consumer with its variable consumption.
2. Link of the automated system
Any automatic control and regulation system consists of separate elements that perform independent functions. Thus, the elements of an automated system can be subdivided according to their functional purpose.
Each element transforms some physical quantities characterizing the course of the regulation process. The smallest number of such values for an element is two. One of these quantities is the input and the other is the output. The transformation of one quantity into another that occurs in most elements has only one direction. For example, in a centrifugal governor, changing the shaft speed will move the clutch, but moving the clutch by an external force will not change the shaft speed. Such elements of the system, which have one degree of freedom, are called elementary dynamic links.
The control object can be considered as one of the links. A diagram that reflects the composition of the links and the nature of the connection between them is called a structural diagram.
The relationship between the output and input values of an elementary dynamic link under conditions of its equilibrium is called a static characteristic. Dynamic (in time) transformation of values in the link is determined by the corresponding equation (usually differential), as well as by the totality of the dynamic characteristics of the link.
The links that are part of a particular system of automatic control and regulation may have different principle actions, miscellaneous design etc. The classification of links is based on the nature of the dependence between the input and output values in the transient process, which is determined by the order of the differential equation that describes the dynamic transformation of the signal in the link. With such a classification, the entire constructive variety of links is reduced to a small number of their main types. Consider the main types of links.
The amplifying (inertialess, ideal, proportional, capacitive) link is characterized by instantaneous signal transmission from input to output. In this case, the output value does not change in time, and the dynamic equation coincides with the static characteristic and has the form
Here x, y are the input and output values, respectively; k is the transmission coefficient.
Examples of amplifying links are a lever, a mechanical transmission, a potentiometer, a transformer.
The lagging link is characterized by the fact that the output value repeats the input value, but with a delay Lm.
y(t) = x(t - Xt).
Here t is the current time.
An example of a lagging link is a transport device or pipeline.
Aperiodic (inertial, static, capacitive, relaxation) link converts the input value in accordance with the equation
Here G is a constant coefficient characterizing the inertia of the link.
Examples: room, air heater, gas holder, thermocouple, etc.
An oscillatory (two-capacitive) link converts the input signal into a signal of an oscillatory form. The dynamic equation of the oscillatory link has the form:
Here Ti, Tr are constant coefficients.
Examples: float differential pressure gauge, diaphragm pneumatic valve, etc.
The integrating (astatic, neutral) link converts the input signal in accordance with the equation
An example of an integrating link is an electrical circuit with inductance or capacitance.
The differentiating (pulse) link generates at the output a signal proportional to the rate of change of the input value. The dynamic equation of the link has the form:
Examples: tachometer, damper in mechanical transmissions. The generalized equation of any link, control object or automated system as a whole can be represented as:
where a, b are constant coefficients.
3. Transient processes in systems automatic regulation. Dynamic characteristics of links
The process of transition of a system or object of regulation from one equilibrium state to another is called a transition process. The transient process is described by a function that can be obtained as a result of solving the dynamic equation. The nature and duration of the transition process are determined by the structure of the system, dynamic characteristics its links, a kind of perturbing influence.
External perturbations can be different, but when analyzing a system or its elements, they are limited to typical forms of influences: a single step (jump-like) change in time of the input value or its periodic change according to the harmonic law.
The dynamic characteristics of a link or system determine their response to such typical forms of impacts. These include transient, amplitude-frequency, phase-frequency, amplitude-phase characteristics. They characterize the dynamic properties of a link or an automated system as a whole.
The transient response is the response of a link or system to a single step action. Frequency characteristics reflect the response of a link or system to harmonic fluctuations in the input value. The amplitude-frequency characteristic (AFC) is the dependence of the ratio of the amplitudes of the output and input signals on the oscillation frequency. The dependence of the phase shift of the oscillations of the output and input signals on the frequency is called the phase-frequency characteristics (PFC). Combining both of the mentioned characteristics on one graph, we get a complex frequency response, which is also called the amplitude-phase response (APC).
The transient response is determined by solving the corresponding dynamic equation or experimentally, the frequency response can also be found from experience or obtained by analyzing the dynamic equation using operational calculus methods.
Integral Laplace transform
To simplify and make more visual the analysis of the dynamic equation of a link or an automated system as a whole, the operational method is widely used in the theory of automatic control. This method, based on the integral Laplace transform, consists in the fact that not the function itself (original) is studied, but some modification of it (image).
The Laplace transform, which determines the relationship between the original ff(t) and the image Ffs), has the form:
where s is some complex value (s= i- imaginary unit.
The essence of the operational method is that the original differential equation containing the original f(t) is reduced using the Laplace transform to an algebraic equation with respect to the image F(s), and the value s is considered as a certain number. The resulting algebraic equation is resolved with respect to the function F(s), and then the reverse transition is made from the image F(s) to the original f(t), which is the desired one.
Transition procedure from original to image ( direct conversion Laplace) is represented by the symbol £[Am)|, and the procedure for transition from the image to the original (the inverse Laplace transform) is represented by the symbol L-"\F(s)].
From expression (2.1), the main properties of the Laplace transform can be revealed.
2. The image of the product of a function by a constant coefficient is equal to the product of this coefficient by the image of the function
1. The image of the sum of several functions is equal to the sum of the images of these functions
3. The image of the constant is determined by the expression
6. The image of the function integral is determined by the dependence
 |
If at the initial moment of time (τ > 0) the function /(τ) and its derivatives up to order n-1 inclusive take on zero values, then expression (2.8) will take the form:
For the convenience of the practical use of the operational method in engineering problems, on the basis of expression (2.1), ready-made relations for images of various functions are obtained. Images of some of the most commonly used functions are shown in Table. 2.1.
Table 2.1
Pictures of some features
The considered properties of the Laplace transform and the available formulas for the connection of originals and images allow you to quickly find the original from the image of the function or vice versa.
Analysis of the differential equation of the link dynamics by the operational method. Transmission function
Applying the Laplace integral transform to the differential equation (1.7) under zero initial conditions (when the desired function and all its derivatives vanish at r = 0), we obtain
Here F(s), X($) are images of the functions y and jc, respectively. Equation (2.11) can be represented as
Here the complexes A(s), B(s), fV(s) are defined by the expressions
Thus, the dynamic equation in images has a form similar to 
in (boome with the static characteristic of the link (1.1)
The function W(s) included in expressions (2.12), (2.16) is the ratio of the output signal image to the input signal image and is called the transfer function.
The transfer function fV(s) in the dynamic equation is analogous to the transfer coefficient k in the static characteristic.
The transfer functions of typical links and some objects of regulation are given in Table. 2.2.
The transfer function of the system of links depends on the way they are combined.
The transfer function of series-connected links is equal to the product of the transfer functions of these links
Here i is the link number; i is the number of links.
Transfer functions of typical links and some objects of regulation
The transfer function of parallel connected links is equal to the algebraic sum of the transfer functions of these links
The transfer function of the feedback circuit is given by
where fV\(s) is the transfer function of the forward circuit; fV^s) - transfer function feedback; the "+" sign corresponds to negative feedback, and the sign of positive feedback.
Solution of the dynamic equation. Transient response calculation
From expression (2.16), taking into account (2.13) - (2.15), it follows that by applying the integral Laplace transform to a linear differential dynamic equation under zero initial conditions, one can obtain the dependence for the image of the desired function in the form
where P(s), Q(s) are some polynomials with respect to the variable s.
Applying the inverse Laplace transform to the function Y(s), we obtain the solution of the original dynamic equation
where si is the 1st root of the polynomial Q(s); q is the number of roots; Q\s) is the derivative of the function Q(s) with respect to the variable s.
Taking into account (2.22), the solution of the dynamic equation takes the form
where S is some numerical coefficient.
Solution (2.23) can be used, in particular, to calculate the transient response. For this, it is necessary to describe the approximate analytical function a single step change of the input value and using this function to form polynomials P(s) and Q(s). For an approximate description of a single step change in the input value, the function can be used
Thus, if the expression for the transfer function is known, then using dependence (2.25) it is easy to form polynomials P(s) and Q(s). For example, for an aperiodic link, the transfer function of which, in accordance with Table. 2.2 is determined by the relation
polynomials P(s) and Q(s) have the form
Polynomial of the third degree (2.28) has 3 roots: s/=0; S2=-S; s 3 =-
The derivative Q"(s) of the function Q(s) has the form
and its values, substituted into expression (2.23), are determined by the relations
Taking into account (2.27), (2.30), expression (2.23) for calculating the transient response will take the form
Similarly, the solution of the dynamic equation is obtained with an arbitrary change in the input value. In this case, instead of function (2.24), another function is chosen that describes the change in the input value.
frequency characteristics
If the transfer function of a link, object or system is known, then their frequency characteristics can be found by replacing the variable s in this function with the product w, where i is the imaginary unit, » is the circular frequency. The function of the complex variable fV(ico) obtained as a result of such a replacement can be represented in trigonometric or exponential forms
Here A(co) is the ratio of the amplitudes of the output and input signals; cp^co) - phase shift between the output and input signals.
The dependence of the relative amplitude A(co) on the frequency co is the amplitude-frequency characteristic (AFC), and the dependence of the phase shift cp(co) on the frequency co is the phase-frequency characteristic (PFC).
On the complex plane, the function W(ico) can be represented as the geometric sum of the real R(co) and imaginary I(co) parts.
Dependence (2.34) determines the complex frequency response, which is called the amplitude-phase characteristic (AFC).
Between the functions A(a>), (p^co), R(a>), 1(a>) there is a one-to-one relationship
Obtaining the frequency response, phase response, AFC, consider the example of an oscillatory link with a transfer function determined by the relation
Multiplying the numerator and denominator of expression (2.38) by the value (l-T^aP-iTito), we get rid of irrationality in the denominator
From the condition of identity of expressions (2.34), (2.39) we obtain relations for the quantities R(a>) and 1(a>)
Further analysis is performed using expressions (2.34) -(2.36).
Table 2.3
Graphs of transient processes and amplitude-phase characteristics of typical links
Examples of graphs of transients and amplitude-phase characteristics for various links are given in Table. 2.3.
Dynamic equation of a heated room
The dynamic equation reflects the dependence of the indoor air temperature on the regulatory and control actions, as well as on time.
Considering the room as an object with lumped parameters and assuming the temperature of the internal air to be constant in its volume, we obtain the equation for the heat balance of the air in the room in the form:
where p is the air density in the room; c p is the specific isobaric heat capacity of air; U - internal air temperature; V is the volume of the room; g - time; Q c - heat flow transferred to the room by the heating system; Q„ om - heat flow due to heat losses through the building envelope.
The heat flux Q c for instrumental heating systems is determined by the relation
and for systems air heating, ventilation and air conditioning
Here, the heat transfer coefficient and the heating area of the heating
body appliances, respectively; to is the average coolant temperature; G - mass air flow in the air heating, ventilation or air conditioning system; t np - supply air temperature.
The heat flux Opot is expressed by the dependence
where k, F - heat transfer coefficient and area of enclosing structures, respectively; U- outdoor air temperature.
The regulation of the temperature of the internal air and when using instrumental heating systems can be carried out by changing the temperature of the coolant and or its flow rate, on which the heat transfer coefficient kp depends. In air heating systems, regulation is carried out by changing the supply air temperature t np or its flow rate G.
Depending on the heating system and the method of regulation, the form of the dynamic equation also changes. So for the air-
heating when controlling the temperature t e by changing the supply air flow or its temperature t„ P, the dynamic equation of the heated room takes the form
For instrument heating systems, when controlling the temperature te by changing the temperature of the coolant and the dynamic equation of the heated room has the form
More complex view has a dynamic equation when using instrument heating systems with temperature control and by changing the flow rate of the coolant. To obtain it, it is necessary to know the relationship between this flow rate and the heat transfer coefficient kn. The influence of the coolant flow rate on the heat transfer coefficient depends on the type of coolant (water or steam), design and material heating appliances, the thickness of their walls, the intensity of heat transfer to the surrounding air.
Dynamic equation of a ventilated room
The dynamic equation characterizes the change in concentration harmful substances indoors in time, depending on the characteristics of air exchange.
Let at the initial moment of time the concentration of harmful substances in the room be equal to c. At this point in time, the source of emission of harmful substances with the intensity of Measures begins to operate in the room and the general ventilation system is turned on. We will consider the volumetric performance of the supply and exhaust ventilation systems to be the same and equal to L. We will assume that harmful substances are distributed evenly over the volume of the room, and their concentration at all its points is the same and equal to c. Let us designate the concentration of harmful substances in the supply air as cn and, taking into account the assumptions made, we will draw up an equation for their balance in the room
From equation (3.7) we obtain the dynamic equation of a ventilated room
Here, the controlled parameter is the concentration c, and the regulation itself is carried out by changing the performance ventilation system L.
Dynamic equation of mixing heat exchanger
The scheme of the mixing heat exchanger together with the scheme of automatic control of the heat carrier temperature is shown in fig. 3.1. *
Cold water with a mass flow rate G\ and dry saturated steam with a mass flow rate Gi are supplied to the inlet of the mixing heat exchanger. At the outlet of the heat exchanger, a mixture of heated water and condensate is obtained. The automatic control system maintains the temperature of the mixture at a given level. The sensor 2 perceives the change in the temperature of the mixture at the outlet of the heat exchanger and acts on the bellows 3. The bellows 3 moves the jet pipe 5 through the lever transmission 4, which controls the hydraulic servomotor 6. The servomotor 6 moves the valve shutter 7, regulating the steam flow Gi.
Let us obtain a dynamic equation for the mixing heat exchanger, which characterizes the change in the temperature of the mixture over time. To do this, we compose the heat balance equation
Here G CM is the flow rate of the mixture at the outlet of the heat exchanger; from - specific heat water; M is the mass of liquid in the heat exchanger; g - hidden
th heat of vaporization; t is the temperature of the mixture; and - the temperature of the cold water at the inlet to the heat exchanger.
Assuming that the controlled parameter is the temperature of the mixture t, and the regulation is carried out by changing the steam flow rate Gi, from equation (3.9) we obtain the dynamic equation
Similarly, the dynamic equation of the entire automatic temperature control system in the mixing heat exchanger can be obtained. In such an equation, the controlled parameter is also the temperature of the mixture t, but the input parameter will not be the steam flow Gi, but the movement h of the valve shutter.
Dynamic Equation of Automatic Gas Pressure Regulator
The diagram of the automatic pressure regulator is shown in fig. 3.2. The regulator maintains the set pressure Pa in the gas tank or any other object.
When the pressure in the gas holder is equal to the specified /> 0, the pressure force F on the membrane 1 is balanced by the opposition of the spring 2, while the valve stem remains stationary. If the pressure rises for some reason, the valve stem will drop, the valve will open, releasing excess gas into the line, and the pressure p 0 will be restored.
If the regulator is installed on an object with a different pressure p "or in the same gas tank it is required to change the setting to another pressure p 0" (or p 0 "), then the regulator is adjusted to a different pressure by the clamping nut 3. When setting to a higher pressure, the clamping nut is moved up. In this case, the diaphragm, under the influence of additional spring force, will also move up and the valve will close. Reducing the capacity of the valve will increase the pressure. When setting to a lower pressure, the clamping nut is moved down. In this case, set new mode with less pressure.
Let us obtain the dynamic equation of the regulator, which characterizes the change in the time of movement at the valve stem, depending on the change in pressure p. To do this, consider the equilibrium condition for the moving parts of the controller
Here F n is the elastic force of the spring; F u - inertia force of moving parts; F m - the force of friction of moving parts on fixed ones.
The quantities included in equation (3.11) are determined by the expressions
Technological parameters, objects of automatic control systems. The concepts of sensor and transducer. Displacement transducers. Differential and bridge circuits for connecting sensors. Sensors of physical quantities - temperature, pressure, mechanical effort. Control of media levels. Classification and schemes of level gauges. Methods for controlling the flow of liquid media. Variable level and variable differential pressure flowmeters. Rotameters. Electromagnetic flowmeters. Implementation of flowmeters and scope.Ways to control the density of suspensions. Manometric, weight and radioisotope density meters. Control of viscosity and composition of suspensions. Automatic granulometers, analyzers. Moisture meters for enrichment products.
7.1 General characteristics of control systems. Sensors and transducers
Automatic control is based on continuous and precise measurement input and output technological parameters of the enrichment process.
It is necessary to distinguish between the main output parameters of the process (or a specific machine) that characterize the ultimate goal of the process, for example, qualitative and quantitative indicators of processed products, and intermediate (indirect) technological parameters that determine the conditions for the process, the operating modes of the equipment. For example, for a coal cleaning process in a jigging machine, the main output parameters may be the yield and ash content of the products produced. At the same time, these indicators are affected by a number of intermediate factors, for example, the height and looseness of the bed in the jigging machine.
In addition, there are a number of parameters characterizing the technical condition of technological equipment. For example, the temperature of bearings of technological mechanisms; parameters of centralized liquid lubrication of bearings; condition of transshipment units and elements of flow-transport systems; the presence of material on the conveyor belt; the presence of metal objects on the conveyor belt, the levels of material and pulp in the tanks; duration of work and downtime of technological mechanisms, etc.
Of particular difficulty is the automatic on-line control of technological parameters that determine the characteristics of raw materials and enrichment products, such as ash content, material composition of ore, the degree of opening of mineral grains, the granulometric and fractional composition of materials, the degree of oxidation of the grain surface, etc. These indicators are either controlled with insufficient accuracy or are not controlled at all.
A large number of physical and chemical quantities that determine the modes of processing of raw materials are controlled with sufficient accuracy. These include the density and ionic composition of the pulp, volumetric and mass flow rates of process streams, reagents, fuel, air; levels of products in machines and apparatuses, ambient temperature, pressure and vacuum in apparatuses, humidity of products, etc.
Thus, the variety of technological parameters, their importance in the management of enrichment processes require the development of reliable control systems, where the on-line measurement of physical and chemical quantities is based on a variety of principles.
It should be noted that the reliability of the parameters control systems mainly determines the performance of automatic process control systems.
Automatic control systems serve as the main source of information in production management, including automated control systems and process control systems.
Sensors and transducers
The main element of automatic control systems, which determines the reliability and performance of the entire system, is a sensor that is in direct contact with the controlled environment.
A sensor is an element of automation that converts a controlled parameter into a signal suitable for entering it into a monitoring or control system.
A typical automatic control system generally includes a primary measuring transducer (sensor), a secondary transducer, an information (signal) transmission line, and a recording device (Fig. 7.1). Often, the control system has only a sensitive element, a transducer, an information transmission line and a secondary (recording) device.
The sensor, as a rule, contains a sensitive element that perceives the value of the measured parameter, and in some cases converts it into a signal convenient for remote transmission to the recording device, and, if necessary, to the control system.
An example of a sensing element would be the membrane of a differential pressure gauge that measures the pressure difference across an object. The movement of the membrane, caused by the force from the pressure difference, is converted by an additional element (converter) into an electrical signal that is easily transmitted to the recorder.
Another example of a sensor is a thermocouple, where the functions of a sensitive element and a transducer are combined, since an electrical signal proportional to the measured temperature appears at the cold ends of the thermocouple.
More details about the sensors of specific parameters will be described below.
Converters are classified into homogeneous and heterogeneous. The former have input and output values that are identical in physical nature. For example, amplifiers, transformers, rectifiers - convert electrical quantities into electrical quantities with other parameters.
Among the heterogeneous, the largest group is made up of converters of non-electric quantities into electrical ones (thermocouples, thermistors, strain gauges, piezoelectric elements, etc.).
According to the type of output value, these converters are divided into two groups: generator ones, which have an active electrical value at the output - EMF, and parametric ones - with a passive output value in the form of R, L or C.
Displacement transducers. The most widely used are parametric transducers of mechanical displacement. These include R (resistor), L (inductive), and C (capacitive) transducers. These elements change the output value in proportion to the input displacement: electrical resistance R, inductance L and capacitance C (Fig. 7.2).
The inductive transducer can be made in the form of a coil with a tap from the midpoint and a plunger (core) moving inside.
The converters in question are usually connected to control systems using bridge circuits. A displacement transducer is connected to one of the arms of the bridge (Fig. 7.3 a). Then the output voltage (U out), taken from the tops bridge A-B, will change when moving the working element of the transducer and can be evaluated by the expression:
The supply voltage of the bridge (U pit) can be direct (at Z i =R i) or alternating (at Z i =1/(Cω) or Z i =Lω) current with frequency ω.
Thermistors, strain- and photoresistors can be connected to the bridge circuit with R elements, i.e. converters whose output signal is a change in active resistance R.
The widely used inductive converter is usually connected to an AC bridge circuit formed by a transformer (Fig. 7.3 b). The output voltage in this case is allocated to the resistor R, included in the diagonal of the bridge.
A special group is made up of widely used induction converters - differential transformer and ferro-dynamic (Fig. 7.4). These are generator converters.
The output signal (U out) of these converters is formed as an AC voltage, which eliminates the need for bridge circuits and additional converters.
The differential principle of generating an output signal in a transformer converter (Fig. 6.4 a) is based on the use of two secondary windings connected towards each other. Here, the output signal is the vector voltage difference that occurs in the secondary windings when the supply voltage U pit is applied, while the output voltage carries two information: the absolute value of the voltage is about the magnitude of the plunger movement, and the phase is the direction of its movement:
Ū out = Ū 1 – Ū 2 = kX in,
where k is the coefficient of proportionality;
X in - input signal (plunger movement).
The differential principle of generating the output signal doubles the sensitivity of the converter, since when the plunger moves, for example, upwards, the voltage in the upper winding (Ū 1) increases due to the increase in the transformation ratio, the voltage in the lower winding decreases by the same amount (Ū 2) .
Differential transformer converters are widely used in control and regulation systems due to their reliability and simplicity. They are placed in primary and secondary instruments for measuring pressure, flow, levels, etc.
More complex is the ferrodynamic transducers (PF) of angular displacements (Fig. 7.4 b and 7.5).
Here, in air gap magnetic circuit (1) is placed cylindrical core (2) with a winding in the form of a frame. The core is installed using cores and can be rotated on small angleα in within ± 20 o. An alternating voltage of 12 - 60 V is applied to the excitation winding of the converter (w 1), as a result of which a magnetic flux arises that crosses the area of \u200b\u200bthe frame (5). A current is induced in its winding, the voltage of which (Ū out), ceteris paribus, is proportional to the angle of rotation of the frame (α in), and the phase of the voltage changes when the frame is rotated in one direction or another from the neutral position (parallel to the magnetic flux).
The static characteristics of the PF converters are shown in fig. 7.6.
Characteristic 1 has a converter without bias winding (W cm). If the zero value of the output signal is to be obtained not on average, but in one of the extreme positions of the frame, the bias winding should be switched on in series with the frame.
In this case, the output signal is the sum of the voltages taken from the frame and the bias winding, which corresponds to a characteristic of 2 or 2 "if you change the connection of the bias winding to antiphase.
An important property of a ferrodynamic transducer is the ability to change the steepness of the characteristic. This is achieved by changing the value of the air gap (δ) between the fixed (3) and movable (4) plungers of the magnetic core, screwing or unscrewing the latter.
The considered properties of PF converters are used in the construction of relatively complex control systems with the implementation of the simplest computational operations.
General industrial sensors of physical quantities.
The efficiency of enrichment processes largely depends on the technological regimes, which in turn are determined by the values of the parameters that affect these processes. The variety of enrichment processes causes a large number of technological parameters that require their control. To control some physical quantities, it is sufficient to have a standard sensor with a secondary device (for example, a thermocouple - an automatic potentiometer), for others, additional devices and converters are required (density meters, flow meters, ash meters, etc.).
Among a large number of industrial sensors, one can single out sensors that are widely used in various industries as independent sources of information and as components of more complex sensors.
In this subsection, we consider the simplest general industrial sensors of physical quantities.
Temperature sensors. The control of thermal modes of operation of boilers, dryers, and some friction units of machines allows obtaining important information necessary to control the operation of these objects.
Manometric thermometers. This device includes a sensitive element (thermal bulb) and an indicating device connected by a capillary tube and filled with a working substance. The principle of operation is based on the change in the pressure of the working substance in a closed thermometer system depending on the temperature.
Depending on the state of aggregation of the working substance, liquid (mercury, xylene, alcohols), gas (nitrogen, helium) and steam (saturated steam of a low-boiling liquid) manometric thermometers are distinguished.
The pressure of the working substance is fixed by a manometric element - a tubular spring, which unwinds with increasing pressure in a closed system.
Depending on the type of working substance of the thermometer, the temperature measurement limits range from -50 ° to +1300 ° C. The devices can be equipped with signal contacts, a recording device.
Thermistors (thermoresistors). The principle of operation is based on the property of metals or semiconductors ( thermistors) change its electrical resistance with temperature. This dependence for thermistors has the form:
where R 0 – conductor resistance at T 0 \u003d 293 0 K;
α T - temperature coefficient of resistance
Sensitive metal elements are made in the form of wire coils or spirals, mainly from two metals - copper (for low temperatures - up to 180 ° C) and platinum (from -250 ° to 1300 ° C), placed in a metal protective casing.
To register the controlled temperature, the thermistor, as a primary sensor, is connected to an automatic AC bridge (secondary device), this issue will be discussed below.
In dynamic terms, thermistors can be represented as a first-order aperiodic link with a transfer function W(p)=k/(Tp+1), if the time constant of the sensor ( T) is much less than the time constant of the object of regulation (control), it is permissible to accept this element as a proportional link.
Thermocouples. Thermoelectric thermometers (thermocouples) are usually used to measure temperatures in large ranges and above 1000 ° C.
The principle of operation of thermocouples is based on the effect of the occurrence of EMF direct current at the free (cold) ends of two dissimilar soldered conductors (hot junction), provided that the temperature of the cold ends differs from the temperature of the junction. The value of the EMF is proportional to the difference between these temperatures, and the value and range of measured temperatures depends on the material of the electrodes. Electrodes with porcelain beads strung on them are placed in protective fittings.
Thermocouples are connected to the recording device using special thermoelectrode wires. A millivoltmeter with a certain calibration or an automatic DC bridge (potentiometer) can be used as a recording device.
When calculating control systems, thermocouples can be represented, like thermistors, as a first-order aperiodic link or proportional.
The industry produces various types of thermocouples (Table 7.1).
Table 7.1 Characteristics of thermocouples
Pressure Sensors. Pressure (vacuum) and differential pressure sensors received the widest application in the mining and processing industry, both as general industrial sensors and as components of more complex systems for monitoring such parameters as pulp density, media consumption, liquid media level, suspension viscosity, etc.
Devices for measuring excess pressure are called manometers or pressure gauges, for measuring vacuum pressure (below atmospheric, vacuum) - with vacuum gauges or draft gauges, for simultaneous measurement of excess and vacuum pressure - with pressure and vacuum gauges or thrust gauges.
The most widespread are spring-type sensors (deformation) with elastic sensitive elements in the form of a manometric spring (Fig. 7.7 a), a flexible membrane (Fig. 7.7 b) and a flexible bellows.
.
To transfer readings to the recording device, the pressure gauges can be equipped with a displacement transducer. The figure shows inductive-transformer transducers (2), the plungers of which are connected to the sensitive elements (1 and 2).
Devices for measuring the difference between two pressures (differential) are called differential pressure gauges or differential pressure gauges (Fig. 7.8). Here, pressure acts on the sensitive element from two sides, these devices have two inlet fittings for supplying more (+ P) and less (-P) pressure.
Differential pressure gauges can be divided into two main groups: liquid and spring. According to the type of sensitive element, among the spring ones, the most common are membrane (Fig. 7.8a), bellows (Fig. 7.8 b), among liquid - bell (Fig. 7.8 c).
The membrane block (Fig. 7.8 a) is usually filled with distilled water.
Bell differential manometers, in which the sensing element is a bell partially immersed upside down in transformer oil, are the most sensitive. They are used to measure small differential pressures between 0 and 400 Pa, e.g. to monitor vacuum in the furnaces of drying and boiler installations.
The considered differential pressure gauges are scaleless, the registration of the controlled parameter is carried out by secondary devices, which receive an electrical signal from the corresponding displacement transducers.
Sensors of mechanical forces. These sensors include sensors containing an elastic element and a displacement transducer, tensometric, piezoelectric and a number of others (Fig. 7.9).
The principle of operation of these sensors is clear from the figure. Note that a sensor with an elastic element can work with a secondary device - an AC compensator, a strain gauge sensor - with an AC bridge, a piezometric sensor - with a DC bridge. This issue will be discussed in more detail in subsequent sections.
The strain gauge is a substrate on which several turns of a thin wire (special alloy) or metal foil are glued, as shown in Fig. 7.9b. The sensor is glued to the sensing element, which perceives the load F, with the orientation of the long axis of the sensor along the line of action of the controlled force. This element can be any structure that is under the influence of the force F and operates within the limits of elastic deformation. The load cell is also subjected to the same deformation, while the sensor conductor is lengthened or shortened along the long axis of its installation. The latter leads to a change in its ohmic resistance according to the formula R=ρl/S known from electrical engineering.
We add here that the considered sensors can be used to control the performance of belt conveyors (Fig. 7.10 a), measure the mass of vehicles (cars, railway cars, Fig. 7.10 b), the mass of material in bunkers, etc.
Evaluation of conveyor performance is based on weighing a certain section of the belt loaded with material at a constant speed of its movement. The vertical movement of the weighing platform (2) mounted on elastic links, caused by the mass of material on the tape, is transmitted to the induction-transformer converter (ITP) plunger, which generates information to the secondary device (Uout).
For weighing railway cars, loaded vehicles, the weighing platform (4) rests on strain gauge blocks (5), which are metal supports with glued strain gauges that experience elastic deformation depending on the weight of the weighing object.
Automation of heat and gas supply and ventilation systems. 1986
Foreword....3
Introduction...5
Section I. Fundamentals of automation of production processes
Chapter 1. General information....8
1.1 Significance of automatic control production processes....8
1.2 Conditions, aspects and stages of automation....9
1.3 Features of automation of TGV systems .... 11
Chapter 2 Basic concepts and definitions....12
2.1 Characteristics of technological processes .... 13
2.2 Basic definitions....14
2.3 Classification of automation subsystems....15
Section II. Fundamentals of the theory of control and regulation
Chapter 3 Physical basis of control and structure of systems....18
3.1 The concept of managing simple processes (objects) .... 18
3.2 The essence of the management process....21
3.3 The concept of feedback....23
3.4 Automatic controller and the structure of the automatic control system....25
3.5 Two ways of control....28
3.6 Basic principles of control....31
Chapter 4 Control object and its properties....33
4.1 Storage capacity of the object....34
4.2 Self-regulation. Influence of internal feedback....35
4.3 Lag....38
4.4 Static characteristics of the object....39
4.5 Object Dynamic Mode....41
4.6 Mathematical models of the simplest objects....43
4.7 Manageability of Objects....49
Chapter 5 Typical methods for the study of ASR and ACS....50
5.1 The concept of a link in an automatic system .... 50
5.2 Basic typical dynamic links....52
5.3 Operating method in automation....53
5.4 Symbolic notation of dynamic equations....55
5.5 Block diagrams. Connecting links....58
5.6 Transfer functions of typical objects....60
Section III. Technique and means of automation
Chapter 6 Measurement and control of process parameters....63
6.1 Classification of measured values....63
6.2 Principles and methods of measurement (control) .... 64
6.3 Measurement Accuracy and Uncertainties....65
6.4 Classification of measuring equipment and sensors....67
6.5 Sensor Specifications....69
6.6 State system of industrial instruments and automation equipment .... 70
Chapter 7 Means for measuring the main parameters in TGV systems....71
7.1 Temperature sensors....72
7.2 Humidity sensors for gases (air) ......77
7.3 Pressure sensors (vacuum) ...... 80
7.4 Flow sensors....82
7.5 Measuring the quantity of heat....84
7.6 Interface level sensors....85
7.7 Determination of the chemical composition of substances .... 87
7.8 Other measurements....89
7.9 Basic circuits for switching on electrical sensors of non-electrical quantities .... 90
7.10 Totalizers....94
7.11 Signaling Methods....96
Chapter 8 Amplifying-converting devices....97
8.1 Hydraulic boosters....97
8.2 Pneumatic boosters....101
8.3 Electrical amplifiers. Relay....102
8.4 Electronic amplifiers....104
8.5 Multistage Gain....107
Chapter 9 Executive devices....108
9.1 Hydraulic and pneumatic actuators....109
9.2 Electrical actuators....111
Chapter 10 Drivers....114
10.1 Classification of regulators according to the nature of the driving action....114
10.2 Basic types of drivers....115
10.3 ACP and microcomputer....117
Chapter 11 Regulators....122
11.1 Characteristics of distribution bodies....123
11.2 Main types of distribution bodies....124
11.3 Control devices....126
11.4 Static calculations of regulator elements....127
Chapter 12 Automatic regulators....129
12.1 Classification of automatic regulators....130
12.2 Basic properties of controllers....131
12.3 Continuous and intermittent controllers....133
Chapter 13 Automatic control systems....137
13.1 Control statics....138
13.2 Control dynamics....140
13.3 Transients in ASR....143
13.4 Regulating stability....144
13.5 Stability criteria....146
13.6 Control quality....149
13.7 Basic laws (algorithms) of regulation .... 152
13.8 Linked control....160
13.9 Comparative characteristics and selection of a regulator....161
13.10 Controller settings....164
13.11 ACP Reliability....166
Section IV. Technique and means of automation
Chapter 14 Design of automation schemes, installation and operation of automation devices....168
14.1 Fundamentals of automation circuit design....168
14.2 Installation, adjustment and operation of automation equipment .... 170
Chapter 15 Automatic remote control of electric motors....172
15.1 Principles of relay-contactor control....172
15.2 Controlling a squirrel-cage induction motor....174
15.3 Control of a slip-ring motor....176
15.4 Reversing and controlling standby motors....177
15.5 Circuit equipment remote control....179
Chapter 16 Automation of heat supply systems....183
16.1 Basic principles of automation....183
16.2 Automation of district heating plants .... 187
16.3 Automation of pumping units....190
16.4 Automation of replenishment of heating networks....192
16.5 Automation of condensate and drainage devices....193
16.6 Automatic protection of the heating network against pressure increase....195
16.7 Automation of group heating points....197
Chapter 17 Automation of heat consumption systems....200
17.1 Automation of hot water systems .... 201
17.2 Principles of building thermal management .... 202
17.3 Automation of heat supply in local heating points .... 205
17.4 Individual control of the thermal regime of heated rooms .... 213
17.5 Pressure control in heating systems....218
Chapter 18 Automation of low power boiler houses....219
18.1 Basic principles of automation of boiler rooms .... 219
18.2 Automation of steam generators....221
18.3 Technological protection of boilers....225
18.4 Automation of hot water boilers....225
18.5 Automation of gas-fired boilers....228
18.6 Automation of combustion devices of micro-boilers....232
18.7 Automation of water treatment systems....233
18.8 Automation of fuel preparation devices....235
Chapter 19 Automation of ventilation systems....237
19.1 Automation of exhaust ventilation systems....237
19.2 Automation of aspiration and pneumatic transport systems....240
19.3 Automation of aeration devices....241
19.4 Air temperature control methods....243
19.5 Automation of supply ventilation systems....246
19.6 Air curtain automation....250
19.7 Automation of air heating....251
Chapter 20 Automation of artificial climate installations....253
20.1 Thermodynamic fundamentals of SCR automation....253
20.2 Principles and methods of humidity control in SCR....255
20.3 Automation of central air conditioning....256
20.4 Automation of refrigeration units....261
20.5 Automation of autonomous air conditioners....264
Chapter 21 Automation of gas supply and gas consumption systems....265
21.1 Automatic gas pressure and flow control....265
21.2 Automation of gas-using installations....270
21.3 Automatic protection of underground pipelines from electrochemical corrosion ....275
21.4 Automation for liquid gases....277
Chapter 22 Telemechanics and dispatching....280
22.1 Basic concepts....280
22.2 Construction of telemechanics schemes....282
22.3 Telemechanics and dispatching in TGV systems .... 285
Chapter 23 Prospects for the development of automation of TGV systems....288
23.1 Feasibility study of automation....288
23.2 New directions of automation of TGV systems....289
Appendix....293
Literature .... 296
Index....297
