Telemechanical systems, applications of telemechanics

Telemechanics is a field of science and technology that encompasses the theory and technical means of automatically transmitting control commands and information about the status of objects at a distance.

The term «telemechanics» was proposed in 1905 by the French scientist E. Branly for the field of science and technology for remote control of mechanisms and machines.

Telemechanics allows coordinating the work of spatially separated units, machines, installations and, together with communication channels, connects them into a single control system at a distance from production facilities or other processes.

Telemechanics means, together with means of automation, allow remote control of machines and installations without on-duty personnel in local facilities and combine them into single production complexes with centralized control (power systems, rail, air and water transport, oil fields, highway pipelines, large factories, quarries, etc. mines, irrigation systems, city utilities, etc.).

Telemechanical system — a set of telemechanical devices and communication channels designed for the automatic transmission of control information at a distance.

The classification of telemechanical systems is carried out according to the main characteristics characterizing their properties. They include:

• the nature of the messages transmitted;
• functions performed;
• type and location of objects of management and control;
• configuration;
• structure;
• types of communication lines;
• ways of using them to transmit a signal.

According to the functions performed, telemechanical systems are divided into systems:

• remote control;
• television signals;
• telemetry;
• teleregulation.

In Remote Control Systems (RCS) a large number of elementary commands such as "on", "off" ("yes", "no"), intended for various objects (receivers of information), are often transmitted from the control point.

In telesignaling systems (TS) The control center receives the same elementary signals about the state of objects, such as «yes», «no». In telemetry and teleregulation (TI and TP) the value of the measured (controlled) parameter is transmitted.

TC systems are used to transmit discrete or continuous commands to control objects. The latter type includes control commands transmitted to smoothly change the controlled parameter. TC systems intended for the transmission of control commands are sometimes distinguished in an independent classification group from TR systems.

TS systems are used to transmit discrete messages about the status of monitored objects (for example, to turn on or off equipment, reach the limit values ​​of a parameter, occur an emergency condition, etc.).

TI systems are used to transmit continuous controlled values. TS and TI systems are combined into a group of remote control (TC) systems.

In a number of cases, combined or complex telemechanical systems are used, simultaneously performing the functions of TU, ​​TS and TI.

According to the method of transmission of messages, telemechanical systems are divided into single-channel and multi-channel. The majority of systems are multi-channel, transmitting signals over a common communication channel to or from many TC facilities. They form a large number of object subchannels.

The total number of different signals TU, TS, TI and TR in a telemechanical system in railway transport, oil fields and pipelines already reaches thousands, and the number of equipment elements - many tens of thousands.

The control information that telemechanical systems transmit at a distance is intended for the operator or control computer at one end of the system and the control objects at the other.

The information must be presented in a user-friendly form. Therefore, the telemechanical system includes devices not only for the transmission of information, but also for distribution and presentation in a form convenient for perception by the operator or input into a control machine. This also applies to TI and TS data acquisition and preprocessing devices.

According to the type of serviced (monitored and controlled) objects, telemechanical systems are divided into systems for stationary and moving objects.

The first group includes systems for stationary industrial installations, the second — for control of ships, locomotives, cranes, airplanes, missiles, as well as tanks, torpedoes, guided missiles, etc.

According to the location of controlled and controlled objects, unified and dispersed object systems are distinguished.

In the first case, all objects served by the system are located at one point. In the second case, the objects served by the system are scattered one by one or in groups in a number of points that are connected at different points to a common communication line.

Telemechanical systems with unified objects include, in particular, systems for individual power plants and transformer substations, pump and compressor installations. Such systems serve a single point.

Distributed telemechanical systems include, for example, oilfield systems. Here, telemechanics serves a large number (tens, hundreds) of oil wells and other installations distributed in the field and controlled from one point.

Telemechanical system for scattered sites — a type of telemechanical systems in which several or a large number of geographically dispersed controlled points are connected to a common communication channel, each of which may have one or more technical control, technical information or vehicle objects.

The number of dispersed objects and controlled points in systems for centralized control of production, processes in industry, transport and agriculture is much greater than the number of concentrated objects.

In such control systems, relatively small points are scattered along the line (oil and gas pipelines, irrigation, transportation) or over the area (oil and gas fields, industrial plants, etc.). All sites participate in a single, interconnected production process.

An example of a telemechanical system with distributed objects: Remote control in electrical networks

The main scientific problems of telemechanics:

• efficiency;
• reliability of information transmission;
• optimization of structures;
• technical resources.

The importance of telemechanical problems increases with the increase in the number of objects, the volume of transmitted information and the length of communication channels, which reach thousands of kilometers.

The problem of the effectiveness of information transmission in telemechanics lies in the economical use of communication channels through their compaction, that is, in the reduction of the number of channels and their more rational use.

Transmission reliability issues are in eliminating the loss of information during transmission due to the effects of interference and in ensuring hardware reliability.

Optimization of the structure — in the selection of the scheme of communication channels and the equipment of the telemechanical system, which guarantees maximum reliability and efficiency of information transmission.

Selection is based on aggregate criteria. The importance of structure optimization increases with system complexity and with the transition to complex systems with distributed objects and multilevel control.

The theoretical basis of telemechanics consists of: information theory, noise protection theory, statistical communication theory, coding theory, structure theory, reliability theory. These theories and their applications are developed and developed taking into account the specifics of telemechanics.

The most complex and complex problems arise in the synthesis of large remote control systems, including teleautomation systems. For the synthesis of such systems, an integrated approach based on generalized criteria, taking into account the conditions of transmission and optimal processing of information, is even more necessary. This presents a problem for optimal remote control.

Modern telemechanics is characterized by the development of methods and technical means in a wide variety of directions. The number of fields of application of telemechanical systems and the volume of implementation in each of them are constantly expanding.

For several decades, the volume of telemechanics introduced has increased approximately 10 times every 10 years. Below is information on the application areas of telemechanics.

Telemechanics in energy

Telemechanics devices are used in geographically separated facilities at all stages of production and distribution of electricity for control: units (within large hydroelectric power plants), power supply of industrial enterprises, power plants and substations of the power system, power systems.

Electricity is characterized by the presence of several levels of control included in a hierarchical system with a number of control points of different ranks.Power plants and substations are managed by the dispatch point of the power system, and the latter form interconnected power systems.

In this regard, local and centralized functions are performed at each control point.

The first involves the development of control actions for objects served by this point, as a result of processing information coming from objects and from other control points.

To the second - the transfer of transit information from a lower level to control points of a higher level without processing or with partial processing of information, while the transmission of TI and vehicle signals from the control point of a lower level to a higher - the first level is performed.

Most power system sites are large, concentrated. They are located at great distances, measured in hundreds and sometimes thousands of kilometers.

Most often information is transferred through HF communication channels over power lines.

Relatively little information is required to monitor and control power plants and substations in the power system. At this stage, TU-TS devices with time division of signals, single-channel devices of frequency and pulse-frequency TI systems operating through special communication channels are used.

In order to improve the quality of the supplied energy, increase the reliability of the operation of power transmission networks and reduce losses, additional complexity of dispatch control is necessary. These tasks can be solved by the widespread introduction of computing technology at various stages of management.

See also: Telemechanical systems in energy and Dispatch points in the power supply system

Telemechanics in the oil and gas industry

Remote control devices are used for centralized control and management of oil or gas wells, oil gathering points, compressor and other installations in oil or gas fields.

The number of telemechanized oil wells alone is many tens of thousands. The specificity of technological processes for production, primary processing and transportation of oil and gas consists in the continuity and automaticity of these processes, which do not require human intervention under normal conditions.

Telemechanics tools allow you to switch from three-shift service of wells and other sites to one-shift, with an emergency team on duty in the evening and night shifts.

With the introduction of telemechanization, oil field enlargement is often done. Up to 500 wells are centrally controlled, scattered over an area of ​​several kilometers2 to many tens of km2... The number of TU, ​​TS and TI at each compressor station, oil collection station and other installations reaches many tens.

Work is currently underway to combine oilfields into production to maintain optimal oilfield and field facility conditions.

The means of automation and telemechanics allow to change and simplify technologies, processes in oil fields, which gives a great economic effect.

Main pipelines

Telemechanics devices are used for centralized control and management of gas pipelines, oil pipelines and product pipelines.

The services of regional and central dispatchers are organized along the main pipelines.The first includes objects of technical specifications, technical equipment and technical information in pipeline branches, on bypass lines of crossings over rivers and railways. etc., objects of cathodic protection, pumping and compressor stations (taps, valves, compressors, pumps, etc.).

The area of ​​the regional dispatcher is 120 — 250 km, for example between neighboring pumping and compressor stations. TU functions (operational) are performed by the center, by the dispatcher only if they are not entrusted to the district dispatcher.

There is a tendency to reduce technical control facilities with the transfer of these functions to local automation devices, to a transition to centralized management without the service of the district dispatcher or to reduce his functions.

The chemical industry, metallurgy, engineering

In large industrial enterprises, telemechanical devices transmit operational and production-statistical information both for the management of individual industries (technological workshops, energy facilities) and for the management of the entire plant.

With the distances between controlled points and the control point of 0.5 - 2 km, telemechanics successfully competes with remote transmission systems and provides savings due to a reduction in cable length.

Industrial enterprises are characterized by the presence of large concentrated and scattered objects. The first include electrical substations, compressor and pumping stations, technological workshops, the second — objects located one by one or in small groups (valves for supplying gas, water, steam, etc.).

Continuous information is transmitted by intensity telemetry system devices, TI devices with time pulses or code pulses. The latter are usually included in complex TU-TS-TI devices, transmitting discrete and continuous information over a communication channel.

Cable communication lines are mainly used in industrial enterprises.

The increase in the amount of information entering the control center required the automation of its processing. In this regard, complex systems are used that provide information processing for the dispatcher (operator).

Mining and coal industry

In the mining and coal mining industry, telemechanical devices are used to control and monitor concentrated objects located in mines and on the surface, to control mobile dispersed objects in mining areas, to control flow-transport systems. The last two tasks are most specific for the mining and coal mining industry.

In underground works, where, for example, there are devices for telecounling trolleys, telemechanical signals are transmitted by power lines 380 V — 10 kV through busy telephone lines, as well as by combined channels: from a mobile object to a lowering substation — a low-voltage power network, then to the control room — a free or busy pair of wires in a telephone cable. Time and frequency systems TU — TS are used.

Distortion of the work schedule of the flow-transport system disrupts the technological cycle, which is why telemechanical devices must have increased reliability.In this case, cable communication lines are used between the dispatch center, the local control points and the controlled points.

Railway transport

I have railway automation and telemechanical systems in railway transport designed to ensure the safe movement of trains and the urgency of their movement. These two goals are usually achieved simultaneously with such devices. Their damage affects both the safety and the urgency of the movement.

The main requirements for automation and telemechanics devices in this case are the compliance of the devices with the operating conditions — the intensity and speed of movement — and the high reliability of their operation.

Telemechanics devices are used to control the supply of electrified roads and to centralize dispatch (control of switches and signals) within a site (control circuit) or station.

In railway power management there are two independent tasks: control of traction substations, section posts and control of overhead disconnectors. At the same time, the control is carried out within a dispatch circle with a length of 120-200 km, along which 15-25 controlled points are located (traction substations, section posts, stations with air disconnectors).

A TU with catenary disconnectors allows repair work to be carried out without disrupting train timetables. TU disconnectors, located in small groups along the railway, are performed by a special device TU — TS.

More info: Railway automation and telemechanics

Irrigation systems

Remote control devices are used for centralized control and management of water intake and distribution.

It is one of the largest users of telemechanics. They are used to control gravity irrigation systems, main channels and water receiving wells (including water gates, shields, valves, pumps, water level and TI flow, etc.). The length of the irrigation system with remote control is up to 100 km.

SCADA systems in telemechanics

SCADA (short for supervisory control and data acquisition) is a software package designed to develop or provide real-time operation of systems for collecting, processing, displaying and archiving information about a monitoring or control object.

SCADA systems are used in all sectors of the economy, where it is necessary to provide operator control over technological processes in real time.

See here for more details: SCADA systems in electrical installations