At the current level of development of computer technology and network technologies, strict requirements are imposed on networks. The computer network must provide the transfer rate required for specific conditions; it should also be mobile, with a large number of access points, and no cable should be required; the network should be easy to administer; it must provide high reliability with simple technical solutions; the network must support all possible types of network equipment and with all this, it must be cheap.
With the general global computerization of both the common population and enterprises, organizations and special services, it became necessary to organize computer networks
One of the options for organizing networks is a data transmission system over power grids.
The diploma work will show a diagram of the organization of a data transmission network over power grids using the example of Alkhan-Churt using PLC technology
The BZD section is carried out in order to create safe working conditions when working with power supply networks.
In the economic part of the diploma, the cost of the projected network will be calculated and the economic feasibility of building a network based on PLC technology
PLC technology is, first of all, a solution to the "last mile" problem. Because this solution uses the in-house power grid. The service itself is provided on a Plug & Play basis. That is, an adapter or a subscriber modem purchased by a consumer in a store does not require any settings: when plugged into an outlet, a connection is automatically made with the head unit, which is one in each house; the configuration is automatically configured and the IP address is assigned. The advantage of the technology is also the fact that to connect to the Internet there is no need to wait for the fitters and let them into your home. Another additional plus is roaming: the modem works in all homes with PLC coverage. It is not hard-coded to a specific address and works both within the district, and within the city, and in another city too. Now networks are being built simultaneously in five cities, and at least another 5-6 cities in Russia are at the stage of project preparation.
With all the advantages of this technology, the Internet access market is already saturated, and we literally feel on ourselves how slowly the growth of the subscriber base is proceeding. If the client has already connected to the provider and made the wiring, then there is no point in attracting him at a low price, especially since by lowering the prices the operator puts himself in a difficult situation. The average payment for broadband is already low. Therefore, for development, it is necessary to introduce new services and services. For example, the so-called "constructor". Different modules are "attached" to the basic PLC modem: Ethernet socket; Wi-Fi access point; telephone module, to which you can connect a regular analog landline telephone, and an internal device, and a VoIP device. With the help of the latter, you can organize the internal telephone network within the city (for example, direct telephone channels with relatives).
Another plug-in is a video camera, with which you can organize a video surveillance system at home without even connecting it to a computer. It transmits all traffic over the power grid to the provider's server. And a user anywhere in the world can go to the Internet, go to his Personal Area on the client interface and check your home environment. This solution is ideal for monitoring children, babysitters and housekeepers. In addition, various additional functions can be configured through the Web interface, such as a motion detection system (motion control), which will allow the camera to perform the functions of a volumetric motion sensor: when the picture has changed, a signal goes to the server, an SMS is sent to mobile phone user - he connects to the Internet and checks if everything is in order.
PLC (Power Line Communications) technology, also called PLT (Power Line Telecoms), is a wired technology that harnesses the cabling infrastructure of power grids to provide high-speed data and voice communications. Depending on the transmission speed, it is divided into broadband (ВPL) with a speed of more than 1 Mbps and narrowband (NPL).
Powerline broadband Internet service testing has been launched in Scotland. The initiative belongs to Scottish Hydro Electrics. According to the British edition of PC Advisor, about 150 users were involved in testing the "Internet through a socket". Each subscriber got access to the Internet at a speed of 2 Mbps. For the price it was more than doubled more profitable offers another ISP. Several energy companies of the country have already shown interest in the new service. In addition, RWE, Germany's leading electricity supplier, is dynamically implementing PLC. For example, in Germany, people do not even fill out receipts for electricity: the information from the meters comes directly to the electricity supplier through the wiring. Similar projects have been launched in Italy and Sweden.
In Russia, the first stage of building a network based on PLC technology was carried out by Spark and was completed in October 2005. At that time, the network included more than 750 access nodes located in residential buildings. All access nodes are connected by a Gigabit Ethernet backbone optical network. In 2006, a pilot project was launched to commission PLC technology in the South Tushino region, and in 2007, active construction of the network and connection of subscribers began.
The low payment for Internet access ensures good competitiveness, but the quality sometimes causes criticism from potential and current subscribers (judging by the numerous discussions on the forums). For example, users complain about the problem of being able to connect to the Network only through a specific outlet in the apartment, which is not always convenient for the subscriber, as well as about a decrease in speed when turning on electrical appliances. This is due to the general condition of the electrical wiring of the apartment, but such problems are solved by the provider's specialists. In addition, in order to avoid any problems, it is recommended to plug the user device into a separate outlet. Nevertheless, experts in the telecommunications industry adhere to a low assessment of the development potential of PLC networks. The reason for this is the technology itself. To transfer data from computer to computer, the Ethernet technology was specially developed, as a result, when using it, the cost of terminal equipment is the lowest, and the speed characteristics are the best. Any attempts to adapt a medium that was not originally intended for data transmission leads to a higher cost of equipment and worse technical characteristics. This applies to both telephone copper wire (dial-up modems or ADSL) and power networks (PLC technology).
The so-called "last mile problem", which has been so much talked about lately, has given rise to many solutions. However, most of these solutions have one common drawback - they all require laying of wires and cables. Probably, it makes no sense to talk about what difficulties and difficulties this sometimes causes - very often the cost of laying a cable makes up most of the cost of setting up a network. Moreover, there are a number of cases in which laying new cables is impossible or highly undesirable - a striking example of such an unpleasant situation is a recently completed repair, immediately after which it suddenly turns out that it is necessary to lay additional wires for computer networks.
Therefore, special interest has always been aroused by those technologies that made it possible to do without laying new cables. At the moment, there are two successful approaches to this problem - wireless Wi-Fi networks and PLC technologies. Much has been written about wireless networks now, but much less information is available about PLC technologies.
PLC technologies make it possible to build computer local networks based on existing power lines. So, using PLC technology, you can build a small home local area network using the electrical wiring that has already been installed.
In fact, methods of transmitting information using electrical wiring have existed for a long time. One of them is the well-known Soviet loudspeakers (which are also often incorrectly called radio stations). Various technologies are based on a rather simple idea of signal separation - if somehow it were possible to simultaneously transmit several signals over one physical channel, then in this way it would be possible to increase the overall data transfer rate. This can be achieved using modulation (besides, the modulated signal is resistant to interference), and with different modulation methods on the same physical data transmission channels, it is possible to achieve different speed data transmission.
At first glance, the recipe for a successful PLC technology may seem simple - you just need to choose the modulation method that could provide the fastest data transfer, and a modern communication facility is ready. However, those modulation methods that provide the most dense signal packing require complex mathematical operations, and in order for them to be applied in PLC technologies, the use of fast signal processors (DSP) is necessary.
A digital signal processor (DSP) is a specialized programmable microprocessor designed to manipulate digital data streams in real time. DSPs are widely used to process graphics, audio and video streams.
Transmission of information over power supply networks using the IC of the Semtech company (2015)
The Semtech Corporation product range includes a variety of physical layer ICs that allow information to be transmitted both by wire and by radio (optical transceivers, line drivers, radio transceivers, etc.). The acquisition in early 2015 of EnVerv, a leader in the development of PLC (Power Line Communications) modems, allowed Semtech to expand its communications product line with devices that exchange data over standard power lines. Within the framework of this article, we will dwell on the principles of operation and construction of networks based on single-chip PLC microcircuits from Semtech, consider the features of individual representatives of the new family and give examples of practical implementation of devices based on them.
INTRODUCTION
The transmission of information and the organization of power supply over the same wires is used quite effectively in various applications. For example, you can think of standard telephone lines or Ethernet networks that connect remote nodes using a technology in which power is supplied through individual cores of the communication cable. However, most of these solutions have an obvious drawback: they all generally require installation work, the costs of which often make up a large part of the cost of setting up a network. Moreover, there are a number of situations in which the laying of new cables is extremely undesirable or even impossible - an example of such situations is a recently completed repair, after which it suddenly turns out that it is necessary to lay additional wires for computer networks or a rented office with an unintended Internet connection. In these cases, it is almost always possible to limit ourselves to the existing infrastructure, namely, to use the electrical wiring already available in almost every room to organize a relatively fast and reliable communication channel branched out throughout the building.
PLC telecommunication technology, based on the use of power grids for data exchange by superimposing a useful signal on top of a standard alternating current with a frequency of 50 or 60 Hz, is distinguished by its ease of implementation and prompt installation of devices based on it. The first data transmission systems over electric grids appeared in the 1930s, they were mainly used for signaling in power systems and on railways with very low bandwidth. In the late 1990s, a number of companies implemented the first large projects in this area, however, serious problems were identified during operation, the main one of which was poor noise immunity. The operation of energy-saving lamps, switching power supplies, chargers, thyristor dimmers and household electrical appliances, as well as electric motors and welding equipment, especially those switched on in the immediate vicinity of the PLC modem, caused impulse noise in the wires unprotected from high-frequency radiation, which led to a sharp decrease in reliability data transmission. Also, the stability and speed of signal transmission was negatively affected by the heterogeneity of communication lines, in particular, the quality and deterioration of electrical networks, the presence of joints made of materials with different electrical conductivity (for example, copper and aluminum), the presence of twists, etc. As a result, the overall reduction in the nominal data rate ranged from 5 to 50%. In addition, in the rooms where PLC devices were operating, in some cases there was a violation of radio reception at a distance of about 3-5 meters from the modem, especially at medium and short waves. This was due to the fact that the wires of the power grid began to act as antennas for radio repeaters, emitting, in fact, all the traffic on the air.
The technology of data transmission over power grids received due commercial application only at the beginning of this century, and its introduction and widespread use is due to the appearance of an appropriate element base, incl. high-performance microcontrollers and fast DSP processors (digital signal processors), allowing to implement complex signal modulation methods and modern data encryption algorithms. This provided not only high level reliability in the transfer of information, but also its protection from unauthorized access. It was also important to solve the problem of standardizing various aspects of technology. Currently, IEEE, ETSI, CENELEC, OPERA, UPA and HomePlug Powerline Alliance are the main organizations and communities regulating the requirements for PLC devices. The latter is an international alliance that unites about 80 well-known companies in the telecommunications market, including Siemens, Motorola, Samsung and Philips. The alliance, founded in 2000, aims to conduct research and practical testing of the compatibility of devices from different manufacturers using this technology, as well as support and promote a single standard called HomePlug.
All existing PLC systems are usually divided into broadband (BPL - Broadband over Power Lines) and narrowband (NPL - Narrowband over Power Lines). The range of tasks solved with their help is very wide, and the choice of the necessary method is based on the characteristics and volume of the transmitted information. Broadband devices (with speeds from 1 to 200 Mbit / s) are focused on Internet access systems, home computer networks, as well as applications requiring high-speed data exchange: streaming video, video conferencing systems, digital telephony, etc. Of greatest interest to hardware developers are narrowband PLC modems due to their relative cheapness and improved characteristics, which make it possible to work not only in conventional networks, but also in networks with an increased level of interference. Microcircuits and modules for narrowband modems (with channel bandwidth from 0.1 to 100 Kbps) are widely used as part of various household and industrial products, when creating distributed automated control and management systems in workshops and building life support systems (elevators, devices air conditioning and ventilation), metering devices for the consumption of electricity, water, gas, heat, security and fire alarm devices.
FEATURES OF PLC TECHNOLOGY
The basis of PLC technology is the use of frequency division of the signal, in which a high-speed data stream is divided into several relatively low-speed ones, each of which is transmitted on a separate subcarrier frequency and then combined into the resulting signal (Fig. 1).
With conventional frequency division modulation (FDM), the available spectrum is wasted inefficiently. This is due to the presence of guard intervals between individual subcarriers, necessary to prevent the mutual influence of signals (Fig. 2a). Therefore, PLC devices use Orthogonal Frequency Division Multiplexing (OFDM), in which the centers of the subcarriers are located so that the peak of each subsequent signal coincides with the zero value of the previous one. As seen in Fig. 2b, the available frequency band in this case is spent more rationally.
Before being combined into a single signal, all subcarriers are phase modulated, each with its own bit sequence. After that, they pass through the shaping unit, where they are assembled into a single information packet, also called an OFDM symbol. Figure 3 shows an example of Differential Quadrature Phase Shift Keying (DQPSK) for each of the four subcarriers in the 4.5-5.1 MHz range. In reality, in the PLC technology, transmission is carried out using 1536 subcarriers with the choice of 84 best ones in the range from 2 to 32 MHz, depending on the current state of the line and the presence of interference. This method gives PLC technology flexibility for use in various conditions. For example, as mentioned above, a working PLC device is capable of jamming radio reception at certain frequencies, this problem is well known to radio amateurs. Another example is when an application is already using part of a range. Technically, the elimination of unwanted mutual influence is implemented by using the settings, the so-called Signal Mode and Power Mask, on devices that provide the corresponding option. Signal Mode is a software method for determining the operating frequency range, and Power Mask is a software method for limiting the spectrum of the frequencies used. Due to this, PLC devices can easily coexist in the same physical environment and not noise the frequency ranges used for radio communication.
When transmitting signals over a household power supply, significant attenuation of the transmitted signal at certain frequencies can occur, which can lead to loss and corruption of data. To solve the problem of adaptation to the physical transmission medium, a method is provided for dynamically turning on and off the signal transmission, which makes it possible to detect and eliminate errors and conflicts. The essence of this method lies in the constant monitoring of the transmission channel in order to identify the part of the spectrum that exceeds a certain attenuation threshold. If this fact is detected, the use of the problem band is temporarily stopped until an acceptable attenuation value is restored, and data is transmitted at other frequencies (Fig. 4).
Another significant difficulty in transmitting data over a household power network, now for the PLC devices themselves, is impulse noise, the sources of which can be various chargers, halogen lamps, turning on or off various electrical appliances (Fig. 5). The complexity of the situation lies in the fact that, using the above method, the PLC-modem does not have time to adapt to rapidly changing conditions, because their duration may not exceed one microsecond, as a result, some of the bits may be lost. To solve this problem, a two-stage (cascade) error-correcting coding of bit streams is used before they are modulated and enter the data transmission channel. Its essence consists in adding redundant ("guard") bits to the original information stream according to certain algorithms, which are used by the decoder on the receiving side to detect and correct errors. Cascading a block Reed-Solomon code and a simple convolutional code decoded using the Viterbi algorithm allows you to correct not only single errors, but also bursts of errors, which significantly increases the integrity of the transmitted data. In addition, anti-jamming coding increases the security of transmitted information from the point of view of protection against unauthorized access.
Since an extensive network of household power supply has been selected as the data transmission medium, several connected devices can start transmission at the same time. In such a situation, a regulatory mechanism is used to resolve traffic collision conflicts - the CSMA / CA Medium Access Protocol. Collision resolution occurs on the basis of one or another priority, which is set in special fields for prioritizing data packets.
SEMTECH IC FOR PLC TECHNOLOGY IMPLEMENTATION
Semtech PLC products are designed for use on typical low or medium voltage power lines. Any modem that works with an analog physical line must have the functional units necessary to process analog data, convert it to digital form, and, of course, to process digital data. On the transmission side, the modem must also encode digital data in accordance with the specified algorithm, convert it to analog and send it to the line.
All these actions are performed by the EV8xxx series microcircuits. Narrowband systems-on-a-chip chips are highly integrated and contain all the necessary building blocks to implement the physical, MAC, and other protocol layers (6LoWPAN and IEC). They support several types of modulation; in practice, OFDM is most often used to organize a stable and noise-immune communication channel. The SICs that have passed interoperability testing in the HomePlug Alliance Netricity are versatile and can be used as the basis for both endpoint and network coordinator designs. The Netricity specification is designed for network communications over long-haul power lines and is intended for off-building infrastructure, smart power distribution and industrial process control. The technology can be used in both dense urban and rural power grids using frequencies below 500 kHz. It also includes an IEEE 802.15.4 (MAC) -based access layer, which is key to the development of hybrid wired / wireless networks. The main technical characteristics of Semtech PLC microcircuits are presented in Table 1.
The EV8xxx series ICs have programmable frequency ranges from 10 to 490 kHz, covering CENELEC A (10 - 95 kHz), CENELEC B (95 - 120 kHz), CENELEC C (120 - 140 kHz), FCC (10 - 490 kHz) and ARIB (10 - 490 kHz) bands without changes in the design of the device. By remotely loading the corresponding built-in software over the power line, they can be configured to operate in ITU-T G.9903 (G3-PLC), ITU G.9902, ITU-T G.9904 (PRIME), IEEE P1901.2 and IEC-61334 (S-FSK) modes ). In addition, they support the proprietary high performance 4GPLC mode. Structurally, the microcircuits of the family are manufactured in low-profile surface-mount cases designed for operation in the operating temperature range from -40 to + 85 ° C. A simplified structure depicting the main functional units is shown in Fig. 6, here the following blocks can be distinguished:
The AFE (Analog Front-End) block is a set of analog components that provide isolation using a transformer with a decoupling capacitor, filtering and amplifying the input signal, and shaping the specified levels of the output transmitted signal by using the line driver on the op amp;
PHY is a block designed to interface the digital part of the microcircuit with an analog line;
32-bit RISC microcontroller provides in-circuit implementation of the MAC-level, performs data processing, packet formation, data encoding according to the symmetric AES block cipher algorithm, etc., and also solves applied problems;
Peripheral blocks that interface the built-in microprocessor with external microcircuits - EEPROM memory, ADC with high resolution and a host controller. For communication, the hardware implementation of the widespread SPI, I2C and UART interfaces is used;
Integrated RAM and flash memory. The size of the built-in program memory varies from 1 to 2 MB, the operative memory - from 256 kbytes for the EV8100 to 384 kbytes for the rest, other options are possible upon request to the manufacturer;
Clock control unit;
A power subsystem that provides all the voltages required for individual nodes. Typically, a source is used that operates on the same AC mains as used for data transmission.
Separately, it is worth noting the EV8100 IC, which, in addition to typical units, contains an integrated 6x33 segment LCD display controller and a touch keyboard driver.
APPLICATIONS FOR EV8XXX FAMILY ICs
Semtech PLC microcircuits are focused primarily on the use in automation systems, remote control and monitoring of remote objects, the most popular areas of their application:
Building Automation Networks (AMI);
Landing light control systems at airports;
;
Home local area networks;
Intelligent equipment (“smart things”), incl. consumer electronics;
Control and management systems for solar power plants;
Street lighting networks;
Communication equipment with substations;
Traffic management systems.
Among the above, the main focus is AMI (Smart Metering Infrastructure) networks that integrate smart meters, data concentrators, energy management tools, displays and other components of building automation systems (Figure 7).
Power line communication is the main element of automated systems for monitoring and metering energy carriers used by utilities. The main advantages of this technology: the ability to automatically receive information from residential and industrial premises located in remote areas with low population density and low quality infrastructure, long service life, scalability and low costs. The principle of the system is quite simple. Electricity from the power plant is transmitted through a high-voltage cable to the substation. Here, the voltage is reduced and distributed to a large number of low-voltage transformer substations, which reduce the voltage to household. Typically 500 to 1000 end consumers are connected to one transformer. Thus, the following option for constructing PLC systems for these purposes can be proposed: a concentrator acting as a central unit is based on low-voltage substations and regularly (for example, once an hour) collects measurement results from meters (these can be not only electricity meters, but also water, heat, gas). Then the information is sent to the server for further processing, for example, via the GSM channel. This type of system is not limited only to receiving information from meters and can perform other functions.
For the practical implementation of this system, Semtech offers a developer starter kit, which includes both ready-made solutions based on the EV8000, EV8100 and EV8200 microcircuits for the fastest possible organization of data transmission over the PLC network, as well as debugging tools for assessing the system's capabilities (Table 2).
The latter are modules for end nodes (counters) and hubs, the delivery set of which includes everything you need, including recommendations for use, as well as software for configuring the parameters of individual nodes and monitoring the quality of communication in the projected network. Attached graphical interface the user allows you to program the operating frequency range, modulation type, transmission rate, output power level, etc., as well as to visually track the PER and BER error rates in the received data packets.
Debug kits EVM8K-01, EVM8K-02 and EVM8K-03 can act both as remote measurement nodes and as data collection hubs. The modules are designed for operation in single- and three-phase networks and are powered from a built-in 80-280 V AC source (EVM8K-01 and EVM8K-02) or from a 12 V DC supply (EVM8K-01 and EVM8K-03). Communication with the host controller is carried out via RS-232 or USB interfaces. The EVM8K-13 kit is a network hub that combines an EV8000-based PLC modem with a 32-bit RISC microcontroller on a single PLC card to run a custom application. The set is capable of servicing up to 500 end nodes (up to 2000 optional), among the distinctive features we can note the presence of a “onboard” 3G / EDGE / GPRS modem, GPS module and 8 GB SD card. In addition to wireless transmission data to the server, you can also use the RS-232, USB or Ethernet interfaces. The appearance of the debug kits is shown in Fig. eight.
CONCLUSION
The widespread use of low-voltage electrical networks 0.22-0.38 kV and the absence of the need for costly installation work for laying cables stimulate an increased interest in electrical networks as a data transmission medium. The current development of PLC technology is largely associated with the emergence of generally accepted regulatory standards and the improvement of the corresponding element base. Semtech's PLC modems, featuring a high degree of integration, provide a stable and noise-free communication channel with a sufficiently high bandwidth.
BIBLIOGRAPHY
1. Okhrimenko V. PLC technology. // Electronic components. 2009. No. 10. with. 58-62.
2. Official website of the Semtech company. www.semtech.com
3. Product brochure. EV8000: Single-chip multimode PLC modem.
4. Product brochure. EV8010: Single-chip standards-based PLC modem.
5. Product brochure. EV8020: Single-chip standards-based PLC modem.
6. Product brochure. EV8100: Split-meter display SoC with integrated PLC.
7. Product brief. Power line communication products.
At the current level of development of computer technology and network technologies, strict requirements are imposed on networks. The computer network must provide the transfer rate required for specific conditions; it should also be mobile, with a large number of access points, and no cable should be required; the network should be easy to administer; it must provide high reliability with simple technical solutions; the network must support all possible types of network equipment and with all this, it must be cheap.
With the general global computerization of both the common population and enterprises, organizations and special services, it became necessary to organize computer networks
One of the options for organizing networks is a data transmission system over power grids.
The diploma work will show a diagram of the organization of a data transmission network over power grids using the example of Alkhan-Churt using PLC technology
The BZD section is carried out in order to create safe working conditions when working with power supply networks.
In the economic part of the diploma, the cost of the projected network will be calculated and the economic feasibility of building a network based on PLC technology
PLC technology is, first of all, a solution to the "last mile" problem. Because this solution uses the in-house power grid. The service itself is provided on a Plug & Play basis. That is, an adapter or a subscriber modem purchased by a consumer in a store does not require any settings: when plugged into an outlet, a connection is automatically made with the head unit, which is one in each house; the configuration is automatically configured and the IP address is assigned. The advantage of the technology is also the fact that to connect to the Internet there is no need to wait for the fitters and let them into your home. Another additional plus is roaming: the modem works in all homes with PLC coverage. It is not hard-coded to a specific address and works both within the district, and within the city, and in another city too. Now networks are being built simultaneously in five cities, and at least another 5-6 cities in Russia are at the stage of project preparation.
With all the advantages of this technology, the Internet access market is already saturated, and we literally feel on ourselves how slowly the growth of the subscriber base is proceeding. If the client has already connected to the provider and made the wiring, then there is no point in attracting him at a low price, especially since by lowering the prices the operator puts himself in a difficult situation. The average payment for broadband is already low. Therefore, for development, it is necessary to introduce new services and services. For example, the so-called "constructor". Different modules are "attached" to the basic PLC modem: Ethernet socket; Wi-Fi access point; telephone module, to which you can connect a regular analog landline telephone, and an internal device, and a VoIP device. With the help of the latter, you can organize an internal telephone network within the city (for example, direct telephone channels with relatives).
Another plug-in is a video camera, with which you can organize a video surveillance system at home without even connecting it to a computer. It transmits all traffic over the power grid to the provider's server. And a user anywhere in the world can access the Internet, enter his personal account on the client interface and check the situation at home. This solution is ideal for monitoring children, babysitters and housekeepers. In addition, various additional functions can be configured through the Web interface, such as a motion detection system (motion control), which will allow the camera to perform the functions of a volumetric motion sensor: when the picture has changed, a signal is sent to the server, an SMS is sent to the user's mobile phone - it connects to the internet and checks if everything is ok.
PLC (Power Line Communications) technology, also called PLT (Power Line Telecoms), is a wired technology that harnesses the cabling infrastructure of power grids to provide high-speed data and voice communications. Depending on the transmission speed, it is divided into broadband (ВPL) with a speed of more than 1 Mbps and narrowband (NPL).
Powerline broadband Internet service testing has been launched in Scotland. The initiative belongs to Scottish Hydro Electrics. According to the British edition of PC Advisor, about 150 users were involved in testing the "Internet through a socket". Each subscriber got access to the Internet at a speed of 2 Mbps. At a price it was more than double the price offered by another ISP. Several energy companies of the country have already shown interest in the new service. In addition, RWE, Germany's leading electricity supplier, is dynamically implementing PLC. For example, in Germany, people do not even fill out receipts for electricity: the information from the meters comes directly to the electricity supplier through the wiring. Similar projects have been launched in Italy and Sweden.
In Russia, the first stage of building a network based on PLC technology was carried out by Spark and was completed in October 2005. At that time, the network included more than 750 access nodes located in residential buildings. All access nodes are connected by a Gigabit Ethernet backbone optical network. In 2006, a pilot project was launched to commission PLC technology in the South Tushino region, and in 2007, active construction of the network and connection of subscribers began.
The low payment for Internet access ensures good competitiveness, but the quality sometimes causes criticism from potential and current subscribers (judging by the numerous discussions on the forums). For example, users complain about the problem of being able to connect to the Network only through a specific outlet in the apartment, which is not always convenient for the subscriber, as well as about a decrease in speed when turning on electrical appliances. This is due to the general condition of the electrical wiring of the apartment, but such problems are solved by the provider's specialists. In addition, in order to avoid any problems, it is recommended to plug the user device into a separate outlet. Nevertheless, experts in the telecommunications industry adhere to a low assessment of the development potential of PLC networks. The reason for this is the technology itself. To transfer data from computer to computer, the Ethernet technology was specially developed, as a result, when using it, the cost of terminal equipment is the lowest, and the speed characteristics are the best. Any attempts to adapt a medium that was not originally intended for data transmission leads to a higher cost of equipment and worse technical characteristics. This applies to both telephone copper wire (dial-up modems or ADSL) and power networks (PLC technology).
The so-called "last mile problem", which has been so much talked about lately, has given rise to many solutions. However, most of these solutions have one common drawback - they all require laying of wires and cables. Probably, it makes no sense to talk about what difficulties and difficulties this sometimes causes - very often the cost of laying a cable makes up most of the cost of setting up a network. Moreover, there are a number of cases in which laying new cables is impossible or highly undesirable - a striking example of such an unpleasant situation is a recently completed repair, immediately after which it suddenly turns out that it is necessary to lay additional wires for computer networks.
Therefore, special interest has always been aroused by those technologies that made it possible to do without laying new cables. At the moment, there are two successful approaches to this problem - wireless Wi-Fi networks and PLC technologies. Much has been written about wireless networks now, but much less information is available about PLC technologies.
PLC technologies make it possible to build computer local networks based on existing power lines. So, using PLC technology, you can build a small home local area network using the electrical wiring that has already been installed.
In fact, methods of transmitting information using electrical wiring have existed for a long time. One of them is the well-known Soviet loudspeakers (which are also often incorrectly called radio stations). Various technologies are based on a rather simple idea of signal separation - if somehow it were possible to simultaneously transmit several signals over one physical channel, then in this way it would be possible to increase the overall data transfer rate. This can be achieved using modulation (besides, the modulated signal is resistant to interference), and with different modulation methods on the same physical data transmission channels, you can achieve different data rates.
At first glance, the recipe for a successful PLC technology may seem simple - you just need to choose the modulation method that could provide the fastest data transfer, and a modern communication facility is ready. However, those modulation methods that provide the most dense signal packing require complex mathematical operations, and in order for them to be applied in PLC technologies, the use of fast signal processors (DSP) is necessary.
A digital signal processor (DSP) is a specialized programmable microprocessor designed to manipulate digital data streams in real time. DSPs are widely used to process graphics, audio and video streams.
Thus, the development of PLC technologies was limited by the pace of development of DSP processors, and as soon as the latter began to cope with advanced algorithms for efficient modulation, new technologies for organizing such networks appeared. At the moment, OFDM-modulation is used in PLC technologies, which allows achieving high data transfer rates and good signal immunity to interference.
Broadband Internet access;
Home and office computer networks;
VoIP - IP telephony;
High-speed audio and video transmission;
Office and home (including via the Internet) video surveillance, construction of remote video monitoring systems;
Construction of digital data transmission channels for industrial and home automation (AIIS KUE, ACS TP (SCADA), ACS);
Security systems (fire and burglar alarms).
The success of the business of telecommunications operators, as well as the effective functioning of departmental and corporate networks communication.
Fiber-optic communication lines provide data transmission at high speed, but they have not yet reached the mass user, finding wide application, as a rule, in the corporate sector.
In the mass market of subscriber access today, the most popular is the xDSL technology, which provides users with access to the Internet and other infocommunication services via existing telephone lines. A certain share in this segment is also occupied by such technologies as broadband wireless radio access and satellite access, access over networks cable TV, packet data transmission in networks cellular communication 2.5G / 3G (GPRS / EDGE / UMTS, CDMA 2000 1X / EV-DO).
Factors such as the widespread prevalence of 0.2¸0.4 kV electrical networks, the absence of the need for expensive construction of cable ducts, breaking through walls and laying communication cables, etc., stimulate the study of power networks as an alternative data transmission medium and the development of another broadband access technology - on power grids.
First and second generation PLC equipment was developed. The achieved maximum data transfer rate did not exceed 10-14 Mb / s. The real data transfer rate in PLC test networks using this equipment differed by an order of magnitude and amounted to 1-2 Mb / s. In addition, the PLC subscriber equipment had a relatively high cost, and for the power lines "compacted" by the PLC, a high level of electromagnetic radiation was characteristic, due to the operation of the PLC equipment.
Therefore, until recently, PLC technology was used for the commercial provision of telecommunications services on a limited scale, being uncompetitive with other technologies, and above all xDSL. However, the latest advances in microelectronics, which have allowed the creation of third-generation PLC systems that provide data transfer rates of up to 200 Mb / s using standard power lines, open up new opportunities for implementing broadband access.
Modern PLC systems, focused on solving the problem of broadband subscriber access, mainly use two technologies. The first uses a signal from the so-called. spread spectrum (SS), which significantly increases the noise immunity of transmission. When using SS modulation, the signal power is distributed over a wide frequency band, and the signal becomes invisible against the background of interference. On the receiving side, significant information is extracted from the noise-like signal using a pseudo-random code sequence that is unique for this signal. With the help of different codes, it is possible to transmit several messages at once in one wide frequency band. The described principle underlies the code division multiple access (CDMA) technique. Note that in addition to noise immunity, SS-modulation provides a high level of information security. QPSK modulation is used as the basic one.
The second technology is based on Orthogonal Frequency Division Multiplex (OFDM). This method also guarantees high transmission fidelity and robustness against signal distortion.
A further development of the second option was the technology proposed by the American company Intellon. Here, a modified OFDM method is applied, in which the original data stream is divided into packets, and each of them is transmitted in the frequency range 4.3-20.9 MHz using relative phase modulation on its own subcarrier (DBPSK or DQPSK - Differential Quadrature Phase Shift Keying , Differential Quadrature Phase Shift Modulation). The maximum information transfer rate reaches tens of Mbit / s.
PLC technology implements the point-to-point multiple access principle. A local transformer substation supplies a certain number of buildings with electricity and, at the same time, provides connected users with data transmission services, IP telephony, etc.
The main terminal equipment should be considered a PLC modem, which usually implements an interface for communication with a PC: USB, or Ethernet. Thus, the modem is connected to a source of information - a 220V socket, and at the output through the appropriate interface to a PC. A variant is possible when a telephone supporting VoIP mode is connected in parallel with a PC.
A typical functional diagram and the main components of a PLC modem are shown in Fig. 1.1.
Rice. 1.1. PLC Modem Components
The connection to the Internet in this innovative technology is called Broadband over power lines (BPL).
Unlike a DSL connection, over a home network, technology allows more people to have broadband Internet access.
PLC technology is the cheapest way to create a home network, since it does not require the user to install additional power cables and allows the residents of an entire neighborhood to be connected to the PLC network. One master device can provide access to the Internet via a PLC network for 500 users. To do this, users must have in their apartments adapter devices containing PLC modems.
Of course, most of the successful projects for organizing broadband access via power grids have been implemented in the United States, the homeland of the Internet. Such companies are known as New Visions (New York), Communications Technologies (Virginia), Cinergy (Ohio).
In Germany, PLCs offer Vype; Piper-Net and PowerKom; in Austria - Speed-Web; in Sweden - ENkom; in the Netherlands - Digistroom; in Scotland - Broadband.
In 2005, the Russian Federation began to deploy Internet access networks through household electrical networks using PLC technology.
Internet access is evolving, and soon it will be possible to connect to the Internet even in your country house, where there are no telephone and cable lines.
In most cases, PLC systems are classified according to the voltage of the mains on which they are used and the coverage area (territory):
used on high voltage lines (HV);
used on medium voltage lines (MV);
used on low voltage lines (LV):
last mile;
inside the building;
indoors (apartment).
The PLC includes B, which provides data transfer rates in excess of 1 Mbps, and NPLs at much lower data rates.
When transmitting signals over a household power supply, large attenuation in the transmitting function at certain frequencies can occur, which can lead to loss of data. PowerLine technology provides special method The solution to this problem is dynamically turning off and on data-carrying signals. The essence of this method is that the device constantly monitors the transmission channel in order to identify a portion of the spectrum exceeding a certain attenuation threshold. If this fact is detected, the use of these frequencies is temporarily stopped until the normal attenuation value is restored.
There is also the problem of impulse noise (up to 1 microsecond), which can be caused by halogen lamps, as well as turning on and off powerful household appliances equipped with electric motors.
No matter how optimistic the results of the work of experimental PLC networks abroad, in our country this technology runs the risk of facing a number of difficulties. Domestic electrical wiring is made mainly of aluminum, and not copper, which is used in most countries of the world. Aluminum wires have poorer electrical conductivity, which results in faster signal decay. Another problem is that we still have not resolved the main issues of legal regulation of the use of such technologies. However, the latter is also relevant for the West. The main constraint on the rapid development of high-speed PLC systems is the lack of standards for broadband PLC systems and, as a result, the high risk of incompatibility with other services using the same or similar frequency bands. In 2001, the HomePlug Powerline Alliance, an international consortium, adopted the industry standard for building home networks over electrical lines - the HomePlug 1.0 specification. But this standard regulates the construction of "home" networks, that is, networks within one apartment (cottage). A full-fledged standard for broadband PLC has not yet been developed.
The main organizations and communities involved in the standardization of various aspects of this technology are IEEE, ETSI, CENELEC, OPERA, UPA and the HomePlug Powerline Alliance.
IEEE announced the creation of a group that will develop the BPL standard. The project is called IEEE P1675, "Standard for Broadband over Power Line Hardware".
In addition to IEEE P1675, there are three more areas:
IEEE P1775, initiated to regulate PLC equipment, EMC requirements, test and measurement methods;
IEEE P1901, "Standard for Broadband over Power Line Networks: Medium Access Control and Physical Layer Specifications", which provides a description of the physical layer and the media access layer for all classes of BPL devices;
IEEE BPL Study Group, “Standardization of Broadband Over Power Line Technologies,” enabling the creation of new BPL related groups.
The European Telecommunications Standards Institute has formed the ETSI Technical Committee Power-Line Telecommunications (TC PLT), which is responsible for PLC standardization.
CENELEC is a non-profit organization made up of the National Electrotechnical Committees of the EU Member States, which is the most significant organization in the EU in the field of electromagnetic field standardization. For PLCs, CENELEC creates PLC specifications for the physical layer and the media access sublayer; the corresponding standard EN55022 has been adopted.
The Open PLC European Research Alliance (OPERA) consortium was established in 2004 as part of the European Broadband for All program to promote high-speed Internet access technologies. OPERA's work consists of two stages, each of which takes two years to complete.
The main initiator and source of funding is the European Commission. The total budget is more than 20 million euros, a significant part of the amount is allocated under the FP6 program. The completion of the OPERA project is expected in 2008. In total, more than 30 companies and research institutes from 12 countries are participating in the project.
The OPERA specifications that have been prepared to date cover PHY, MAC and data transmission equipment for power supply networks.
UPA was officially announced in December 2004. The main declared goal of UPA is to promote PLC technologies and demonstrate to the governments of countries and industrial leaders the prospects for its large-scale use. UPA develops standards and regulations to ensure the rapid development of the PLC market. Provides market participants with knowledge of open standards based on interoperability and security.
For the widespread introduction and development of HomePlug technology (one of the first power line transmission technologies), standardization and compatibility of devices from different manufacturers using this technology, the HomePlug Powerline international industrial alliance was organized in 2000. Today more than 80 companies are sponsors, members of the alliance, and also adhere to its recommendations. Among them are such well-known companies as: Motorola, France Telecom, Philips, Samsung, Sony, Matsushita, Sanyo, Sharp, Panasonic and many others. The registered mark of the HomePlug Certified alliance on a product from any manufacturer means that this device meets all the requirements of the HomePlug Powerline standard and is fully compatible with similar devices from another manufacturer.
The first HomePlug Powerline Specification 1.0 is based on Power technology Package ™ offered by Intellon (USA) and accepted as a standard by members of the HomePlug Powerline Alliance. The standards adopted to date and under preparation are presented in table. 1.1.
Table 1.1. HomePlug Powerline Alliance Core Standards
| Name | Date of adoption | Note |
| HomePlug 1.0 | June 2001 | Defines technology to provide data transfer rates up to 14 Mbps |
| HomePlug 1.0 Turbo | An evolution of the 1.0 specification with a maximum data transfer rate of up to 85 Mbps | |
| HomePlug AV | Defines PLC technology with transfer rates up to 200 Mbps. The specification provides for the provision of the quality of service required for the transmission of audio and video streams. Encryption - 128-bit AES | |
| HomePlug Command and Control | September |
Defines the control and management of HomePlug devices |
| HomePlug BPL | Under construction |
Today development in the field of PLC is carried out by several hundred companies engaged in both the production of microcircuit sets and the creation of complete devices on their basis. Here are just a few of the industry players: ABB, Adaptive Networks, Alcatel, Ambient Corporation, Amperion, Ascol, Cisco Systems, Cogency, Corinex, Current Technologies, DataSoft, DefiDev, DS2 (Design of Systems on Silicon), Echelon, Eicon, Electricom, Enikia, Ericsson Austria AG, HP, llevo, Intellon, Krone AG, Linksys, Lucent Technologies, Metricom Corporation, Mitsubishi, Netgear, Northern Telecom, Nor.Web, Philips, PowerNet, PowerWAN, Schlumberger, Schneider Electric, Sumitomo Electric Industries, Telkonet ...
The undisputed leader in the production of ICs (chips) for third-generation PLC systems is Design of Systems on Silicon Corporation - DS2 (Spain). It was founded in 1998 and manufactures a functionally complete set of products that allows you to implement a complete solution for the problem of broadband access based on the PLC. One of the first DS2s presented at the end of 2003 a number of third-generation ICs, providing exchange rates up to 200 Mb / s. DS2 products do not yet support HP v.AV.
Basic IC DS2:
DSS9001: based on this IC, PLC modems and In-Door class equipment can be implemented;
DSS9002: Emitters and Repeaters can be implemented on the basis of this IC;
DSS9003: Specialized IC for interfacing the power grid and fiber-optic communication lines;
DSS9010: Dedicated IC for high-speed solutions
The implementation of a PLC system based on DS2 products is shown in Fig. 1.2.
Rice. 1.2. Implementation of a PLC system based on DS2 products.
Another leader should be recognized the company Intellon Corporation (USA), which was one of the co-founders of the HomePlug alliance. Intellon has prepared the following ICs for the HomePlug v.1.0 specification: INT51X1, INT5200, INT5500CS. In September 2002, the company introduced the world's first certified HomePlug 1.0 module - the RD51X1-AP device for organizing an access point to the Internet using PLC technology. In November 2005, the company announced its 3 millionth product for PLC networks.
For broadband access (HomePlug v.AV specification) Intellon has prepared an INT6000 IC kit. In August 2005, it was announced that the investment arm of Motorola Ventures had begun investing in Intellon's efforts to develop the INT6000 IC suite. The first deliveries are expected in Q2 2006.
Intellon's developments implement PowerPacket technology, which uses an efficient spectrum modulation technique that allows data to be transmitted over power lines at very high speeds. The data transfer speed can be up to 100Mb / s. PowerPacket is a system with characteristics that allow it to adapt to environments with strong multipath reflections, strong narrowband interference, impulsive noise without alignment.
SPiDCOM Technologies (France, www.spidcom.com) is one of the leading developers of element base for PLC / BPL solutions (BPL stands for broadband powerline, the abbreviation used in the USA for PLC). The latest development of the company - an IC of the SPC200 type provides a transfer rate of about 220 Mb / s. Its serial production began in March 2005. The SPC200 variant, which is compatible with the HomePlug v.AV standard, will go on sale in Q2. 2006 IMS SPC200 uses a range of 2 - 30 MHz, divided into 7 operating bands.
The Israeli company Yitran Communications Ltd is actively cooperating with the HomePlug Powerline Alliance. As a result of the research carried out in March 2006, the Yitran solution was chosen as the base technology in the preparation of the HomePlug v.AV standard (section "Commands and Control").
The company has prepared two third-generation ICs: ITM1 and ITC1. They allow you to realize a peak speed of up to 200 Mb / s. The block diagram of a communication device based on IC ITM1 / ITC1 is shown in Fig. 1.3.
Rice. 1.3. Block diagram of a communication device based on IC ITM1 | ITC1.
Yitran Communications has developed and patented Differential Code Keying (DCSK) technology to create high-performance, low-cost network components. DCSK details are not known; it is only reported that it is based on physical medium independent methods of adaptive SS-modulation in the 4-20 MHz frequency band with turbo compensation and code compression.
Hardware components (transceivers) based on DCSK provide significantly more high speed transmission, noise immunity and information protection than existing CEBus-transceivers, at a noticeably lower cost of devices. Several products have been announced, in particular ITM1 (data transfer rate up to 2.5 Mbps) and ITM10 (data transfer rate up to 12 Mbps).
XELine (South Korea) develops both ICs and equipment for PLC solutions. The company offers a third-generation IC of the XPLC40A type, which provides access speeds up to 200 Mb / s.
Another Xeline product, the XPLC21 type IC, provides access speeds up to 24 Mb / s. On its basis, an Emitter, a repeater and a PLC-modem can be realized. This IC is based on an ARM9 processor. The used frequency range is 2-23 MHz. The block diagram of the XPLC21 is shown in Fig. 1.4.
Figure 1.4. Block diagram of IC type XPLC21
The rest of the suppliers are still in the testing stage of the third generation PLC-IC, continuing to release the second generation and generation 2.5 equipment, the so-called. HomePlug v.1.turbo standard (speed up to 85 Mb / s).
On the basis of the sets of ICs discussed above, vendors produce PLC equipment for both the In-Door segment and the segment of integrated solutions (for access at the last mile).
Below we will indicate the manufacturers of third-generation In-Door equipment.
The German company devolo AG produces a line of dLAN PLC products, which belong to the In-Door class and allow you to create an indoor local area network based on PLC technology.
In March 2006, devolo AG announced that it had prepared for the release of a new product line dLAN 200, which provides information transfer rates up to 200 Mb / s (HomePlug v.AV) and is implemented on the basis of Intellon's ICs.
One of the leaders in the segment of local area network equipment, NETGEAR (USA) has also shown interest in the segment of PLC adapters - in February 2006, NETGEAR entered into an agreement with DS2 to start joint work and supply third generation ICs that will allow mastering the production of PLC devices supporting speeds up to 200 Mb / s. The start of deliveries of new products is scheduled for the third quarter of 2006.
The ELCON company (Germany) in March 2006 announced the release of the ELCONnect P-200 model, which is implemented on the basis of the DS2 IC, supports the Ethernet interface and provides exchange rates up to 200 Mb / s.
Table 1.2. D52 Chipset Specifications
| Constructive | DSS9011 | DSS9010 | DSS9001 | DSS9002 | DSS9003 | DSS7700 |
| PBGA196 | PBGA196 | PBGA196 | PBGA256 | PBGA304 | QFN84 | |
| Interfaces | ||||||
| GIMMI | 2 | |||||
| MII | 1 | 1 | 2 | |||
| TDM | 1 | 1 | ||||
| SPI | 1 | 1 | 1 | 1 | 1 | 1 |
| UART | 1 | 1 | 1 | 1 | 1 | |
| GPIO Pins | 9 | 9 | 9 | 9 | 9 | |
| Networking capabilities | ||||||
| MAC addresses | No | 32 | 64 | 1024 | 256k | No |
| QoS and broadcast | There is | There is | There is | There is | There is | No |
| CoS | No | No | There is | There is | There is | No |
| VLAN | 1 | 32 | 32 | 32 | ||
| Functional purpose of devices | ||||||
| CPE | + | + | + | + | ||
| Repeater | + | + | + | |||
| Head end | + | + | + | |||
Table 1.3. DS2 product positioning
| Name | Appointment | Note | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| DSS9010 | High-speed home multimedia applications | QoS management. 802.1d bridging functionality with up to 32 MAC addresses | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| DSS9011 | Low cost solution for audio transmission | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| DSS9001 | Advanced Home Applications and Entry-Level PLC Infrastructure | Supports up to 64 MAC addresses. Designed for use as part of client terminal equipment (CPE). Has an integrated VoIP port | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| DSS9002 | Access infrastructure equipment | Supports up to 1024 MAC addresses. It can be used in: 1) modems and repeaters of low-voltage networks; 2) gateways between medium-voltage and low-voltage networks; 3) gateways of individual apartments or buildings | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| DSS90D3 | Advanced access infrastructure equipment and optical gateways for metropolitan (Metro) networks | Supports up to 262144 MAC addresses. Provides fast reconfiguration using optimized Spanning Tree protocol | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| DSS7700 | Analog unit for head unit  , [A / m]
ENEPD - the maximum permissible energy load of the component of the electric field strength during the work. days [(W / m) 2 × h] ENNPD - the maximum permissible energy load of the component of the magnetic field strength during the work. days [(A / m) 2 × h] The normalized parameter of the electromagnetic field in the frequency range 300 MHz -300 GHz is the maximum permissible value of the energy flux density.
ППЭПД - the limiting value of the energy flux density [W / m2], [μW / cm2] K - coefficient of attenuation of biological effects ENPEPEPD is the maximum permissible value of en. load [W / m2 × h] T - action time [h] Prev the value of the PPED is not more than 10 W / m2; 1000 μW / cm2 in a production room. In residential buildings with round-the-clock irradiation in accordance with СН Þ PPEpd not more than 5 μW / cm2. A decrease in the components of the strengths of the electric and magnetic fields in the induction zone, in the radiation zone - a decrease in the energy flux density, if the given technological process or equipment allows. Time protection (limiting the time spent in the area of the source of the electromagnetic field). Distance protection (60 - 80 mm from the screen). A method of shielding a workplace or a radiation source of an electromagnetic field. Rational layout of the workplace in relation to the true radiation of the electromagnetic field. The use of warning devices. The use of personal protective equipment. A person cannot remotely determine whether the installation is energized or not. The current that flows through the human body affects the body not only at the points of contact and along the path of current flow, but also on such systems as the circulatory, respiratory and cardiovascular systems. The possibility of electrical injuries occurs not only when touched, but also through the step voltage and through the electric arc. Email current passing through the human body has a thermal effect, which leads to edema (from redness to charring), electrolytic (chemical), mechanical, which can lead to rupture of tissues and muscles; therefore, all electrical injuries are divided into local and general (electrical shocks). Local electrical injuries: electrical burns (under the influence electric current); electrical signs (pale yellow spots); metallization of the skin surface (ingress of molten metal particles of an electric arc on the skin); electrophthalmia (burns of the mucous membrane of the eyes). 1st degree: without loss of consciousness 2nd degree: with loss Grade 3: without affecting the work of the heart 4 degree: with damage to the heart and respiratory organs An extreme case is a state of clinical death (cardiac arrest and impaired oxygen supply to brain cells). They are in a state of clinical death for up to 6-8 minutes. Ι. Touching live parts that are energized ΙΙ. Touching disconnected parts that may be energized: in case of residual charge in case of erroneous switching on of the electrical installation or inconsistent actions of the operating personnel in the event of a lightning discharge into an electrical installation or near, touching metal non-current-carrying parts or related electrical equipment (housings, enclosures, fences) after the voltage transition to them from live parts (an emergency occurs - breakdown on the case) ΙΙΙ. Damage by the voltage of a step or a person's stay in the field of spreading electric current, in the event of a ground fault ΙV. Damage through an electric arc at a voltage of an electrical installation above 1 kV, when approaching an unacceptably small distance V. Action of atmospheric electricity during gas discharges VΙ. Releasing the energized person Touch voltage is the potential difference between points in an electrical circuit that a person touches at the same time, usually at the points where the arms and legs are located. The step voltage is the potential difference j1 and j2 in the field of current spreading over the earth's surface between points located at a step distance (»0.8 m). grounding; grounding; protective shutdown. In our case, an artificial protective grounding device is used. All equipment is subject to grounding, as well as the racks in which this equipment is located. A ground loop must be laid around the perimeter of the room where the equipment is located to protect people and equipment from static electricity. Protective grounding should be carried out in accordance with PUE and SNiP 3.05.06-85 ("Electrical devices"). Cases of electric shock to a person are possible only when the electrical circuit is closed through the human body, or, in other words, when a person touches at least two points of the circuit, between which there is some voltage. The occurrence of an electrical injury as a result of exposure to an electric current or an electric arc may be associated with: a) single-phase (single-pole) touch of a person, uninsulated from the ground (base), to uninsulated live parts of electrical installations that are energized; b) with the simultaneous touch of a person to two current-carrying non-insulated parts (phases, poles) of electrical installations under voltage; c) with a person approaching a dangerous distance to non-insulated live parts of electrical installations that are energized; d) with the touch of a person, not isolated from the ground (base), to the metal cases (body) of electrical equipment that is energized; e) with the inclusion of a person who is in the zone of spreading of the earth fault current to the "step voltage"; f) with the action of atmospheric electricity during lightning discharges; g) with the action of an electric arc; h) with the release of a person who is 1-axis under tension. The severity of electrical injuries, assessed by the magnitude of the current passing through the human body and the touch voltage, depends on a number of factors: the circuit for connecting a person to the circuit; the voltage of the network, the circuit of the network itself, the degree of isolation of current-carrying parts from the ground, as well as the value of the capacitance of the current-carrying parts relative to the ground. The most widely used are installations with voltages up to 1000 V with a dead-grounded neutral of a transformer or generator. A four-wire network with a dead-grounded neutral allows you to have two operating voltages: linear 380 V and phase 220 V. There is a three-wire one, with an insulated neutral during normal operation, it is less dangerous, and in an emergency mode, a network with a neutral grounded is safer, therefore, in conditions where there is an aggressive environment and it is difficult to maintain insulation in good condition, preference is given to a four-wire network with a grounded neutral. At voltages above 1000 V, it is allowed to use three-phase networks: three-wire with insulated neutral and three-wire with grounded neutral. With regard to AC networks, the inclusion of a person in an electrical network can be single-phase and two-phase. Two-phase switching, i.e. touching a person simultaneously to two phases, as a rule, is more dangerous, since the highest voltage in this network is applied to the human body - linear, which depends only on the voltage of the network and the resistance of the person, does not depend on the neutral mode I., = 1.73Uph / Rch = Ul / R where 1 „- the value of the current passing through the human body, A; U, - line voltage, i.e. voltage between phase wires of the network, V; Uf - phase voltage (voltage between the beginning and end of one winding or between phase and neutral wires), V. Two-phase connection is equally dangerous in the network, both with isolated and grounded neutral. A single-phase connection occurs much more often, but it is less dangerous than a two-phase one, since the voltage under which a person finds himself does not exceed the phase one, i.e. less than linear by 1.73 times. Accordingly, the current passing through a person turns out to be less. With a single-phase connection, the current value is also influenced by the neutral mode of the current source, the insulation resistance and the capacitance of the wires relative to the ground, the resistance of the floor on which the person is standing, the resistance of his shoes and some other factors. A single-phase network can be isolated from earth or have a grounded conductor. Classification of premises and buildings according to the degree of fire and explosion hazard. ONTP 24–85 All premises and buildings are subdivided into 5 categories: B - premises where technological processes are carried out using flammable liquids with a flash point above 28 ° C, capable of forming explosive and fire-hazardous mixtures when ignited, an excess design explosion pressure of more than 5 kPa is formed. tVSP> 28 ° C; P - over 5 kPa. B - rooms and buildings where technological processes with the use of flammable and hardly combustible liquids, solid combustible substances, which interact with each other or with atmospheric oxygen, can only burn. Provided that these substances do not belong to either A or B. This category is fire hazardous. D - premises and buildings where technological processes are used with the use of non-combustible substances and materials in a combustible, incandescent or molten state. D - premises and buildings where technological processes are processed using solid non-combustible substances and materials in a cold state. The main causes of fires: short circuit, overloading of wires / cables, the formation of transient resistance. Short circuit mode - the appearance as a result of a sharp increase in current strength, electric sparks, molten metal particles, an electric arc, an open fire, ignited insulation. Short circuit reasons: design errors. aging of insulation. moisture insulation. mechanical overload. Fire hazard during overloads - excessive heating of individual elements, which can occur due to design errors in the event of a prolonged passage of current exceeding the nominal value. At 1.5 times the power, the resistors heat up to 200-300 ˚С. Fire hazard of transition resistance - the possibility of ignition of insulation or other nearby combustible materials from the heat arising in the place of the emergency resistance (in transition terminals, switches, etc.). Overvoltage fire hazard - heating live parts by increasing the currents passing through them, by increasing the overvoltage between separate elements electrical installations. Occurs in the event of failure or changes in the parameters of individual elements. Fire hazard of leakage currents - local heating of insulation between individual current-carrying elements and grounded structures. construction planning. technical. methods and means of extinguishing fires. organizational. Construction planning is determined by the fire resistance of buildings and structures (the choice of construction materials: combustible, non-combustible, hardly combustible) and the fire resistance limit is the amount of time during which the load-bearing capacity of building structures is not disturbed under the influence of fire until the first crack appears. All building structures on the limit of fire resistance are divided into 8 degrees from 1/7 hour to 2 hours. For the premises of the exhibition center, materials with a resistance limit of 1–5 degrees are used. Depending on the degree of fire resistance, the greatest additional distances from the exits for evacuation in case of fires are determined (5 degree - 50 minutes). Technical measures are the observance of fire safety standards during the evacuation of ventilation systems, heating, lighting, electrical supply, etc. the use of a variety of protective systems. compliance with the parameters of technological processes and operating modes of equipment. Organizational measures - conducting training on fire safety, compliance with fire safety measures. Decrease in the concentration of oxygen in the air. Lowering the temperature of the combustible substance below the ignition temperature. Isolation of a combustible substance from an oxidizer. Extinguishing agents: water, sand, foam, powder, gaseous substances that do not support combustion (freon), inert gases, steam. A. Chemical foam fire extinguishers. B. Foam fire extinguisher. C. powder fire extinguisher. D. carbon dioxide fire extinguisher, ethyl bromine. Fire protection systems. A. water supply system. B. foam generator. Automatic fire extinguishing system using automatic signaling equipment. A. fire detector (heat, light, smoke, radiation). V. for the computer center, heat detectors of the DTL type, smoke, radioisotope type RID are used. Manual fire extinguishing system (push-button detector). For the VC, carbon dioxide fire extinguishers OU, OA are used (they create a jet of atomized ethyl bromine) and an automatic gas fire extinguishing system, in which freon or freon is used as a fire extinguishing agent. To extinguish fires with water in the automatic fire extinguishing system, sprinklers and drenchers are used. Their disadvantage is that spraying occurs over an area of up to 15 m².
The issue of ensuring the safety of workers of firms and enterprises is still relevant to this day, which is primarily due to the fact that over the past few years the unfavorable situation in industry with labor protection, and in the environment - with the quality of the natural environment has been aggravated. The number and scale of man-made emergencies are growing. In industry, the level of industrial injuries and occupational diseases is growing. The scale of air pollution is also growing. The increase in the scale of production activities, the expansion of the scope of technical systems, the automation of production processes lead to the emergence of new unfavorable factors of the production environment, the consideration of which is a necessary condition for ensuring the required efficiency of activities and preserving the health of workers. Therefore, the project considered possible damaging, dangerous and harmful factors of the working environment, also described the methods and means of ensuring workers' safety, the main measures for electrical safety, environmental protection, the prevention of fires and accidents in the premises and the elimination of the consequences of emergencies. In connection with the above, I believe that the project is safe for the environment and human health due to the following factors: Reliable operation of a large number of devices on the same network is ensured using token transfer technology; Stable operation of the network without failures and interruptions is ensured by the use of the entire operating frequency range for information transmission The number of technical means for organizing a communication channel is minimal (UP - in a single building) The mica coupling capacitor is not explosive The design of the equipment ensures operation in a temperature range from -40 ° C to 85 ° C with a humidity of up to 95% In addition to the above, the PLC-based network does not require maintenance during operation. Today, PLC technology is an interesting and useful product in a special niche, the use of which in individual cases can give a good economic result. The most promising areas of application of solutions: Organization of communication in a cottage or apartment using a ruler Organization of communication in small coaxial networks in rural areas and villages using the Access or In-home line Organization of communication to geographically remote settlements via medium-voltage lines at a distance of 1 km using the Access MV line. But the use of PLC solutions so popular in the West for organizing communications in various administrative buildings may run into problems caused by the specifics of the construction and maintenance of domestic power grids. I would like to remind once again about the need to strictly observe safety rules. Work on electrical networks should be carried out by people who have been instructed and received the appropriate permit. Most understandable about precautions Given the dynamics of the market development, it can be expected that broadband PLC technologies within the next one and a half years can find wide application in a wide variety of industries - from telemetry of utilities resources to multifunctional intelligent systems of individual rooms. After the completion of the work on the main international standards, it is likely that PLC adapters will begin to be embedded in almost all household appliances that provide the ability to exchange data with the "outside world". Considering that there are only two main fixed-line operators in the Czech Republic, the telecommunications market is not fully occupied, and the use and application of PLC technology, as it develops, will make it possible to become one of the leaders in this market segment, both for existing providers and new participants. Simply put, having a small capital, you can create a very promising and competitive organization for the provision of broadband access to the Internet. 1. Savin A.F. PLC is no longer exotic. Communication Bulletin 2. Pavlovsky A. Solomasov S. PLC in Russia. Specificity, problems, solutions, projects. InformCourierSvyaz. 3. Nevdyaev L.M. Bridge to the Internet over power lines. InformCourierSvyaz. 4. Kurochkin Yu.S. "PLC comes to Russia". Connect. 5. Konoplyansky D.K. PLC - data transmission over electrical networks. The last mile. 6. Duffy D. BPL is gaining ground. Networks. 7. Morrisi P. Implementation of BPL technology. Communication networks and systems. 8. Report "PLC technology and its prospects in the Russian market of broadband subscriber access", "Modern Telecommunications" company. 9. Electrical work. In 11 kn. Book. 8. Part 1. Overhead power lines: Textbook. manual for vocational schools / Magidin F. A .; Ed. A. N. Trifonova. - M .: Higher school, 1991 .-- 208 s ISBN 5-06-001074-0 10. "PLC-5 ControlNet Programmable Controllers" - Allen-Bradley 11. "Safety of life" 2009 year. R.A. Gazarov, R.S. Erzhapova, Kh.E. Taimaskhanov, M.S. Khasikhanov, 12. "Finances of the Enterprise" Е.Б. Tyutyukin. 13.http: //www.dchizhikov.boom.ru/works/PlanPLC.htm (Internet through an outlet - analysis of the product offer on the PLC-modem market. Chizhikov Dmitry) 14.http: //www.mrcb.ru/kpk.html?25614 15.http: //network.xsp.ru/5_5.php 16.http: //ru.wikipedia.org - electronic encyclopedia 17.http: //www.datatelecom.ru/technology/plc.html 18.http: //www.tellink.ru 19.https: //www.corinex.com 20.http: //www.bosfa.energoportal.ru/srubric16008-1.htm
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