entranceHigh-frequency communication on LPP. Digital RF communication system MC04-PLC
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The design of the power line, determined by its main purpose - the transmission of electrical energy to the distance, allows it to be used to transmit information. The high level of operation and the large mechanical strength of the lines ensure the reliability of communication channels close to the reliability of the channels on the cable lines of communication. At the same time, when carrying out communication channels for information transfer, it is necessary to take into account the features of lines that make them use for communication purposes. Such a feature is, for example, the presence at the ends of the lines of substation equipment, which can be represented as a chain of consistently connected reactive and active resistance to the wide limits. With these resistances through the tires of substations, the connection is formed between the VL, which leads to an increase in the communication path. Therefore, to reduce the influence between channels and attenuation with the help of special barriers, the pathways of high frequency towers in the direction of substations are blocked.
Significantly increase the attenuation of the branch from VL. These and other features of lines require a number of activities to create information transfer conditions.
The device of the RF channels on the distribution networks 6-10 kV is associated with significant-equipment due to the specifics of the construction of these stresses. In areas of the main lines 6-10 K in between adjacent switching points there are a large number of exhausts, the lines are partitioned by disconnectors and switches, network switching schemes are often changed, including automatically, due to the greater damage of these stresses, their reliability is lower than B71 35 kV and above. The transmission of signals in distribution networks depends on many factors affecting the attenuation of the signal: from the length and number of exhaust, the material of the wire lines, load, etc. The load may vary widely. At the same time, the disconnection of individual exhales, as studies show, sometimes not only does not reduce the attenuation, but, on the contrary, due to the violation of mutual payment compensation between neighboring exhausts increases it. Therefore, the channels even a small length have a significant attenuation and work unstable. At work of the channels, damage to the insulators, poor-quality wire connection and the unsatisfactory status of the switching equipment contacts, these defects are sources of interference, commensurate with the level of the transmitted signal, which can cause termination of the channel and damage to the instrument. The presence on the lines of the partitioning devices leads to a complete cessation of the operation of the RF channel if they are turned off and grounding one of the line sections. The noted disadvantages are significantly limited, although they do not exclude, the use of 6-10 kV lines for the organization of RF channels. Nevertheless, it should be noted that the wide distribution of RF communications on distribution networks has not yet received.
For the purpose of the RF, the communication channels over power lines are divided into four groups: dispatching channels, technological, special and linear operational communication channels.
Without stopping in detail on the use and purpose of each channel of channels, we note that for dispatching and technological channels telephone communication used mainly strip of tonal frequencies 300-3400 Hz<300-2300). Верхняя часть тонального спектра (2400-3400 Гц) не пользуется для передачи сигналов телеинформации. Современная комбинированная аппаратура позволяет организовать в этом спектре до четырех независимых узкополосных каналов телеииформации.
The channels of linear operational communications are used to organize the dispatcher communication with the extensive power line operating on the highway or substations by repair teams, when there is no permanent connection with them. For these channels, simplified transportable and portable telephone equipment is used.
According to the degree of complexity of HF, the channels are divided into simple and complex. Channels consisting only of two sets of terminal RF equipment are called simple. Complex channels are in their composition intermediate amplifiers or several sets of terminal equipment (at the same frequencies).
Equipment of high-frequency communication channels on VL.
Connecting communication equipment to the wires of the power line is carried out using special devices of the so-called equipment of the attachment and processing line consisting of a communication condenser, a barrier and protection elements.
Fig. 21. Scheme of high-frequency communication channel on VL
In fig. 21 shows a scheme for the formation of a communication channel on Vl. Signal transmission of high frequency currents is carried out by transmitters of sealing equipment J, placed at both ends of the VL at substations A and V.
Here, as part of the sealing instruments 1, there are receivers that make the modulated currents of the HF and their conversion. To ensure the transmission of signal energy of the RF voltage by wires, it is sufficient to process at each end of the line one wire using a barrier 5, a communication condenser 4 and an attachment filter 3, which is connected to the sealing equipment 1 using the RF cable 2. To ensure the safety of staff work on the attachment filter When the RF channel runs the grounding knife 6.
Attaching high-frequency equipment according to the scheme Fig. 21 Wears the name phase-land. Such a scheme can be used to form single-channel and multi-channel information transmission systems. Other connection schemes also apply.
If you need to connect to the power transmission line installed on the line track (telephone mobile hardware repair team, the equipment remotely controlled VHF of the radio station, etc.), are usually used, as a rule, antenna connection devices. As an antenna, segments of an isolated wire of a certain length or section of the threshing cable are used.
High-frequency (linear) Barrel has a high resistance for the operating frequency of the channel and serves to boom the path to these currents, reducing their leakage towards the substation. In the absence of a barrier, the attenuation of the channel may increase, since the slight input resistance of the substation shunt the RF channel. The barrier consists of a power coil (reactor), configuration element and protection device. The power coil is the main element of the bar. It must withstand the maximum working currents of the line and currents of the KZ. The power coil is made of copper or aluminum wires of the appropriate section wound on wood-layered plastic rails (delta wood) or fiberglass. The ends of the rivers are fixed on metal crosses. On the upper cross, the configuration element with protective arresters is attached. The setup element serves to obtain relatively high resistance of the barrier on one or several frequencies or frequency bands.
The configuration element consists of capacitors, inductors and resistor coils and turns on in parallel
Power coil. The strength coil and the element of the tuning of the barrier are exposed to atmospheric and switching overvoltages and KZ. The role of protection against overvoltages, as a rule, performs a valve arrester consisting of a spark gap and a nonlinear vilto-resistor.
In the electrical networks of 6-220 kV, the Barreliers of the PT-600-0.25 and KZ-500, as well as barriers with the steel core of the TBS-100 types-100 and V / 100B, differing from each other with a rated current and inductance, stability and geometric parameters The power coil, as well as the type of configuration item and its protection.
Barrels are crashed into a phase power line conductor between a linear disconnector and a communication capacitor. High-frequency barriers can be mounted in a suspended form, on support structures, including on communication condensers.
Communication capacitors are used to connect RF equipment to the air line, while the currents of industrial frequency leakage are discharged through the communication condenser to the ground, bypassing the high frequency instrument. Communication capacitors are calculated on phase voltage (on a network with grounded neutral) and on linear voltage (on a network with an isolated neutral). In our country, condensers of communication of two types are produced: CMR (communication, oil-filled, with an expander) and SMM (communication, oil-filled, in a metal case). For different stresses, condensers are equipped with separate elements connected in series. Communication capacitors can be installed on reinforced concrete or metal supports with a height of about 3 m. For the isolation of the lower element of the capacitor of the CMP body from the body of the support, special porcelain coasters are used.
The attachment filter serves as a link between the condenser of the communication and HF equipment, separating the high voltage line and the installation of the weak current, which is the sealing equipment. The attachment filter ensures that the security of the personnel and the protection of the hardware of high voltage, since the path for the flow of industrial frequency leakage currents are formed by grounding the low-end condenser. With the help of the attachment filter, the wave resistances of the line and high-frequency cable, as well as compensating for the reactive resistance of the communication condenser in the specified frequency band, is carried out. Attachment filters are performed according to transformer and autotransformer schemes and together with communication capacitors form strip filters.
The largest distribution in the organization of RF channels of communication on the power lines of the enterprise was obtained by an OFP-4 attachment filter (see Fig. 19). The filter is enclosed in a steel welded body with a passing insulator to attach a communication condenser and cable funnel to enter the Cable RF. On the wall of the case, a discharger is attached, having an elongated heel to connect the grounding and intended to protect elements of the filter of overvoltages. The filter is designed to attach the RF equipment according to the phase-land scheme complete with communication condensers with a capacity of 1100 and 2200 PF. The filter is set, as a rule, on the support of the communication condenser and is attached to the support bolts at an altitude of 1.6-1.8 m from the ground level.
As noted, all switching in the connections filter circuits are made when the grounding knob is enabled, which serves to ground the lower cover of the communication capacitor during the work of the personnel. A single-pole disconnector for a voltage of 6-10 kV is used as a grounding knife. Operations with a grounding knife are made using an insulating rod. Some types of addition filters have a grounding knife mounted inside the housing. To ensure safety in this case, a separate grounding knife must be installed.
The high-frequency cable is used for electrical connection of the attachment filter (see Fig. 21) with transceiver equipment. When connecting the hardware to the diagram according to the phase diagram - the land applies coaxial cables. The most common is the high-frequency coaxial cable of the RK-75 brand, an internal conductor (single-core or stranded) which is separated from an external braid with insulation from a high-frequency dielectric. The outer screen braid serves as a reverse wire. The external conductor is concluded in a protective insulating shell.
The high-frequency characteristics of the RK-75 cable, as well as conventional communication cables, are determined by the same parameters: wave resistance, kilometer attenuation and speed of electromagnetic waves.
The reliable operation of the RF channels according to the WL provides high-quality and regular execution of planned-preventive work, providing for a whole range of works on the equipment of RF communications on VL. To perform prophylactic measurements, the channels are output from work. The prophylactic service includes planned tests of equipment and channels, the frequency of which is determined by the state of the equipment, the quality of operational service, taking into account preventive work and is set at least 1 time in 3 years. Unplanned channel checks are performed when changing the RF path, damage to the equipment and in the unreliable operation of the channel due to the violation of the regulated parameters.
The separation of the vertically integrated structure of the post-Soviet electric power industry, the complication of the control system, an increase in the share of electricity generation of small generation, new rules for connecting consumers (reducing the timing and cost of connection). At the same time, an increase in the requirements for the reliability of power supply entails a priority attitude towards the development of telecommunications systems.
In the energy sector, many types of communication (about 20) differ in:
- appointment
- transmission medium
- physical principles of work
- type of data transmitted,
- transmission technology.
Among all this variety, the high-voltage lines (VL) of the transmission, which, unlike other species, was created by energy specialists for the needs of the electric power industry. Equipment of other types of communication, initially created for public communication systems, to one degree or another, adapts to the needs of the power companies.
The very idea of \u200b\u200busing the BL for the spread of information signals occurred in the design and construction of the first high-voltage lines (as the construction of a parallel infrastructure for communication systems included a significant rise in price), respectively, the first commercial systems of RF communications are introduced into operation at the beginning of the 20s of the last century.
The first generation of HF communication was more like a radio communication. The attachment of the transmitter and the receiver of high-frequency signals was performed using an antenna with a length of up to 100 m, suspended on the support parallel to the power wire. The same name was the guide for the RF signal - at the time for transmission of speech. Antenna connection has long been used to organize the communication of emergency brigades and railway transport.
The further evolution of HF communications has led to the creation of equipment of RF accession:
- communication capacitors and attachment filters, which made it possible to expand the bands of transmitted and received frequencies,
- HF barriers (barrier filters), which made it possible to reduce the influence of substation devices and inhomogeneity of the VL on the characteristics of the RF signal to an acceptable level, and, accordingly, improve the parameters of the RF path.
The following generations of channel-forming equipment began to transmit not only speech, but also signaling signals, protective teams of relay protection, anti-emergency automation, allowed to organize data transfer.
As a separate type of HF Communication was formed in the 40s, the 50s of the last century. International standards (IEC) were developed, guidelines for the design, development and production of equipment. In the 70s in the USSR, the forces of such specialists as a wharin Yu.P., Skaltsev V.S. Mathematical methodologies and recommendations for calculating the parameters of RF paths were developed, which significantly simplified the work of the design organizations in the design of RF channels and the choice of frequencies, increased the technical characteristics of the inputs of the RF channels.
Until 2014, HF Communication was officially the main type of electric power industry in the Russian Federation.
The emergence and introduction of fiber-optic communication channels, in conditions of widespread distribution of HF communications, has become a complementary factor in the modern concept for the development of electric power communication networks. Currently, the relevance of HF communications remains at the same level, and intensive development and substantial investments in the optical infrastructure contribute to the development and education of new areas of application of the RF connection.
The indisputable advantages and the presence of a huge positive experience of applying the HF Communication (almost 100 years) give reason to believe that the RF direction will be relevant both in the nearest and in the remote future, the development of this type of communication will allow you to solve both current tasks and to promote the development of the entire electricity Industries.
Moscow, May 11 - RIA Novosti. In the book of Vladimir Bogomolov, "The Moment of Truth" about the Great Patriotic War often mentioned "Notes on HF" and the HF communications devices, according to which the Supreme Commander associated with headquarters. The connection was protected, and it was impossible to overhear without the use of special means. What was it for the type of communication?
"HF-Communication", "Kremlinvka", ATS-1 - a system of protected communication channels, which to this day ensures the stability and confidentiality of negotiations of state leaders, ministries, strategic enterprises. Defense methods have become more complicated and improved, but the task remained unchanged: to take care of the state level conversations from foreign ears.
During the Great Patriotic War, according to Marshal I.Kh. Baghamya, "no significant military action began and did not begin and did not begin. The HF communications played an exceptional role as a means of managing troops and facilitated the implementation of combat operations." She was provided not only to the headquarters, but also command directly on the advanced lines, at the sentiments, bridgeheads. Already on the outcome of the war, the most brief contribution of government communications in victory was characterized by the famous Marshal K.K. Rokossovsky: "The use of funds of government communications during the war years made a revolution in the management of troops."
The basis of the government bond appeared in the 1930s, the principle of high-frequency (HF) telephony was laid. It allows you to transfer the human voice, "transferred" to higher frequencies, making it inaccessible to direct listening and allowing the ability to transfer several negotiations on one wire.
The first experiments with the introduction of high-frequency multichannel telephony were conducted from 1921 at the Moscow Plant "Electrosvyaz" under the leadership of V.M. Lebedev. In 1923, a scientist P.V. Shmakov completed experiments on the simultaneous transmission of two telephone negotiations at high frequencies and one at a low frequency on a cable line with a length of 10 km.
A scientist, Professor Pavel Andreevich Azbukin, contributed to the development of high-frequency telephone telephone communications. Under his leadership in 1925, the first domestic equipment of the RF communications was developed on the Leningrad Scientific and Testing Station, which could be used on copper telephone wires.
To understand the principle of telephone HF communications, recall that the usual human voice produces air fluctuations in the frequency band of 300-3200 Hz, and therefore, to transmit sound on a regular telephone channel, a highlighted band is required ranging from 0 to 4 kHz, where sound oscillations will be converted in electromagnetic. You can listen to a telephone conversation on a simple telephone line by simply by connecting the telephone, handset or speaker to the wire. But you can start the wire by a higher frequency band, significantly exceeding the voice frequency - from 10 kHz and above.
© RIA news illustration. Alina Polyanin
© RIA news illustration. Alina Polyanin
This will be the so-called bearing signal. And then the oscillations arising from the human voice can be "hideing" in changing its characteristics - frequencies, amplitudes, phases. These changes of the carrier signal will transmit the sound of the human voice, forming a envelope signal. Attempts to overhear the conversation, connecting to the line by a simple telephone, without a special device will not work - only the high-frequency signal will be heard.
The first lines of government RF communications were extended from Moscow to Kharkov and Leningrad in 1930 and soon the technology has spread throughout the country. By mid-1941, the GF-Communications network included 116 stations, 20 objects, 40 broadcast points and served about 600 subscribers. The work of the engineers of that time also allowed to launch the first automatic station of Moscow in 1930, which later worked for 68 years.
At that time, scientists and engineers solved the tasks of improving the protection of communication lines and at the same time the development of complex encryption equipment. The developed encryption systems were very high and in assessing the leadership of the army largely ensured the success of military operations. Marshal G.K. Zhukov noted: "Good work of encrypters helped win more than one battle." Marshal A.M. adhered to a similar opinion Vasilevsky: "No report on the prepared military-strategic operations of our army has become the property of fascist exploration."
To transmit information between protection and automatics at the ends of the high-voltage line, a channel created for high frequency currents according to the phase-land compound scheme is used.
The tract includes one phase of the active VL, which through the condensers of communication on substations are connected to the ground to create a closed circuit of the RF currents.
The most often on the line use two remote phases "A" and "C" to transmit one of them from the frequency command substation No. 1, and on the second reception at frequency number 2.
Device and appointment of the RF channel. Each substation is installed transmitters and receivers of high-frequency signals. In this case, the modern equipment of RF transceivers is made on the microprocessor base of terminals ETL640 v.03.32 Kopania ABV.
To process signals at each frequency, its transceiver is manufactured. Therefore, for one substation, 2 sets of terminals configured for simultaneous acceptance and transmission of signals in different phases of VL are required.
A special equipment separating high voltage from low-current equipment and creating a highway for transmitting HF signals is engaged in the connection of the RF transceiver to VL. It is completed:
High voltage communication capacitor (COP);
- addition filter (FP);
- high-frequency charger (vz);
- RF cable.
The appointment of a high-voltage communication capacitor consists of reliable isolating from the Earth transported capacities with industrial frequency and through itself high-frequency currents.
On the photograph of the line under consideration, 3 condenser with FP in each phase is installed. They are used to communicate with the far end equipment equipment for purposes:
1. Transferring RH and PA commands;
2. Reception of RZ and PA commands;
3. The works of the RF communications service equipment.
To separate the RF signal from the high-voltage substation equipment to the phase high voltage VL wire, the HF barrage is mounted. which limits the magnitude of the loss of RF signals through parallel contours.
Through it is well undergoing industrial frequency currents and are not skipped high-frequency. The vg consists of a reactor (power coil) that transmits the operating current of the line, and the configuration elements parallel to the reactor connected.
To negotiate the parameters of the input resistances of the RF cable and lines, the attachment filter is used, which is performed by the air transformer model with windings from windings that allow you to perform the necessary adjustments. The RF cable connects the filter of the attachment with a transceiver.
High Frequency Releases (ETL640), Purpose. ETL640 receptioners (PRM / PRD) are intended for transmission and reception of RF signals in the form of commands formed by relay protection (PZ) and anti-emergency automation (PA) to the opposite end of the VL.
Checking the health of the RF Channel. The complex equipment of the RF transmission path is located at distances in hundreds of kilometers, requires control and maintenance of its integrity. The ETL640 receptions at the ends of the VL constantly in the usual operation mode are exchanged (transmitted / receiving) signals of the control frequency.
When the signal is reduced or changed its frequency over the permissible limits, the malfunction signaling is triggered. After restoring the performance, the receptionist in automatic mode is returned to the normal mode of operation.
Exchange signals. Transmission and reception of signals are made on the selected frequencies, for example:
Complex in phase "A": TX: 470 + 4 kHz, RX: 474 + 4 kHz;
- Complex in phase "C": TX: 502 + 4 kHz, Rx: 506 + 4 kHz.
ETL640 equipment is designed for round-the-clock permanent operation in conditions heated ap.
Receiving and transferring commands. Terminals No. 1 and No. 2 of ETL640 complexes are accepted and transmitted on 16 teams from the RH and PA.
Commands of transceivers ETL640.. Typical transceiver commands of any ETL640 complex may look:
1. Turning off the 3-phases of VL-330 kV from the far end of the VL without controlling the ban and start-up and start from the level or SNR complex No. REL-670;
2. Turning off the 3 phases of VL-330 kV from the far end of the VL with control of the measuring organs Z3 DN and the 3rd stage of the NTZNP complex No. ... Protection REL670 without a ban on TAPV and start from the factor of 3 phase disconnection of the complex number ... REL protection;
3. Telepidation of DZ with action on one or 3-phase shutdown of VL-330 kV from the far end voltage, with the control of the parameters of the Z3 DZ of the complex number ... Protection REL670 with OAAPV / TAPV and start from the stage Z3 DZ complex No. ... Rel- Protection 670;
4. Telepidation of NTZNP with an action on one or 3 phase shutdown of VL-330 kV from the far end of the VL with the control of the parameters of the Z3 of the NTZNP complex No. ... Protection REL670 with OAPV / TAPV and starting from the measuring body 3 of the NTZNP complex number ... Protection REL670 ;
5. Fixation of the disconnection of the line for its part of the VL and the action in the scheme of the logic of the AFOL complex number ... Protection of the RZa. Start from the output relay of the scheme of the logic of AFOL complex number ... Protection of the RZ when the line is turned off;
6. III turn he acting on the launch:
- 5th team Akap PRP 232 kHz VL No. ...;
- 2nd commands of the APP 286 kHz VL No. ...;
- 4th signs of Anca PRP 342 kHz VL No. ....
7. Fixing the inclusion of the line for its part and the action in the scheme of the logic of the complex of the complex number ... Protection of the RZA VL with a start-up of the output relay of the scheme of the Logic of the AFOL complex No. ... Protection of the RZ-330, when turning on for its part;
8. Start from the 1st stage of the Sapah scheme ... with the launch:
- the 6th team of Anca PRP 348 kHz Vl No. ...;
- 4th team Akap PRP 122 kHz Vl No. ....
9. 3rd turn turning output with action ...
Each team is formed for specific conditions of the WL, taking into account its configuration in the electrical network and operational conditions. The output relay of the RF equipment and switching devices are located in a separate cabinet.
Chains alarm VL. Terminal alarm. The front panel of the terminals contains 3 LEDs reflecting the state of the REL670 itself and 15 LEDs indicating the protection, faults and the state of operational switches.
The REL670 terminal LEDs (the protection of the 1st and 2nd complexes) and the REC670 (automation and level of the 1st and 2nd complex B1 and B2) of the first six rooms have a red color. LEDs with numbers from 7 to 15 have yellow.
Status indication LEDs. Over the LCD terminal LCD block, 3 LED indicator "Ready", "Start" and "Trip" are inserted. To indicate different information, they are glowing in different colors. The green color indicator is:
Operation of devices - steady luminescence;
- internal damage - blinking;
- Lack of operational current - dimming color.
The yellow indicator indicates:
Starting an emergency registrar - a steady glow ;;
- Finding the terminal in test mode - accompanied by blinking.
The red color of the indicator refers to the issuance of the emergency shutdown command (sustainable glow).
Table of LED Alarm Terminal Reces670
Reset and testing alarm. Reset alarm, counters for taking and transferring RF commands and information on zones of DN and NTZNP for the terminal is made from pressing the SB1 button (alarm reset) on the front side of the cabinet.
To test the LEDs of the REL670 terminals (Reces670), you need to press and hold the SB1 button longer than 5 seconds.
Unchanging light alarm. With the front side of the cabinets of the Reces670 are lamps:
- HLW - works of APV, SNF, Level;
- HLR2 is a malfunction of automation complexes and level B-1IB-2.
The front side of the REL670 cabinets are lamps:
- HLW - work protection;
- HLR1 - a set of protection is derived;
- HLR2 - malfunction of protection complexes.
The face of the ETL cabinets are alarm lamps:
- HLW1 - Malfunction of the ETL of the 1st Complex;
- HLW2 - Fault ETL of the 2nd Complex.
Prospects for the development of air power lines. Time-proven air switches for high-voltage LPP are gradually displaced by modern elegas structures that do not require constant operation of powerful compressor stations to maintain air pressure in tanks and airways.
Burous analog RZA and PA devices for high-voltage equipment, requiring close attention from the service personnel, are replaced with new microprocessor terminals.
Communication channel is a set of devices and physical environments transmitting signals. With the help of channels, the signals are transmitted from one place to another, and also tolerated in time (when storing information).
The most common devices that are part of the channel: amplifiers, antenna systems, switches and filters. A pair of wires, a coaxial cable, a waveguide, a medium in which electromagnetic waves are often used as a physical environment.
From the point of view of communication technology, the most important characteristics of communication channels are distortions that are subjected to signals transmitted on it. There are distortions linear and nonlinear. Linear distortion consist of frequency and phase distortion and are described by the transitional characteristic or, which is equivalent to an integrated channel transmission coefficient. Nonlinear distortions are given nonlinear dependencies indicating how the signal changes when passing over the communication channel.
The communication channel is characterized by a set of signals that are sent on the transmitter end, and the signals that are accepted at the receiving end. In the case when the input and channel output signals are functions defined on a discrete set of argument values, the channel is called discrete. Such communication channels are used, for example, in pulsed modes of operation of transmitters, in telegraph, telemetry, radar.
Several different channels can use the same technical line of communication. In these cases (for example, in multichannel communication lines with frequency or temporal separation of signals), the channels are combined and separated using special switches or filters. Sometimes, on the contrary, one channel uses several technical communication lines.
High Frequency Communication (HF Communication)- This is a type of communication in electrical networks, which involves the use of high-voltage power lines as communication channels. On the wires of the power lines of the power grid flows a current current of 50 Hz. The essence of the organization of the RF communications is that the same wires are used as a signal transmission over the line, but at another frequency.
The frequency range of the RF communication channels is from tens to hundreds of kHz. High-frequency bond is organized between two adjacent substations, which are connected by the power line with a voltage of 35kV and above. In order to enter the tires of the substation distribution device, and the communication signals to the appropriate communication kits are used by high-frequency barriers and communication capacitors.
The RF Capacity has a small resistance to the current industrial frequency and a large resistance at the frequency of high-frequency channels. Communication condenser - On the contrary: has a large resistance at a frequency of 50 Hz, and at the frequency of the communication channel - small resistance. Thus, it is possible to enter the substation tires exclusively with a frequency of 50 Hz, per set of RF communications - only signals at high frequency.
For receiving and processing RF signals on both substations, between which the RF communications is organized, install special filters, signatures of signals and equipment kits that implement certain functions. Below will consider which functions can be implemented using HF-links.
The most important feature is the use of the RF channel in the relay protection devices and automation of the substation equipment.The RF communication channel is used in defenses of lines 110 and 220kV - differential-phase protection and directional high-frequency protection. At both ends, the LAP sets the protection kits that have a connection between themselves on the RF communication channel. Thanks to the reliability, speed and selectivity, protection using the RF communication channel is used as the main for each VL 110-220KV.
Channel for transmission of relay protection signals of power lines (LEP) is called channel relay protection. In the technique of RZa received the greatest distribution of three types of RF Protection:
filter directional,
remote with RF blocking,
differential phase.
In the first two types of protection on a RF channel with an external short circuit, a solid signal of the RF blocking is transmitted, in differential phase protection via the relay protection channel, voltage pulses are transmitted. The duration of pulses and the pause is approximately the same and equal to half the industrial frequency period. With an external short circuit, transmitters located at both ends of the line work in different semi-of industrial frequency. Each of the receivers receives the signals of both transmitters. As a result, with an external short closure, both receiver take a solid blocking signal.
With a short closure on the protected line, the phases of the manipulating voltages are shifted and the time intervals appear when both transmitters are stopped. In this case, an intermittent current occurs in the receiver used to create a signal acting on shutding the switch of this end of the protected line.
Typically, transmitters at both ends of the line operate at one frequency. However, on the lines of high length, there are sometimes relay protection channels with transmitters operating on different RF or PA frequencies with a small interval (1500-1700 Hz). Work on two frequencies makes it possible to get rid of the harmful effects of signals reflected from the opposite end of the line. Relay protection channels use a special (dedicated) RF channel.
There are also devices that, using the RF communication channel, determine the place of damage to the power lines. In addition, the RF communication channel can be used to transmit signals, SCADA, SAU and other ECU control systems. Thus, on the high-frequency channel channel, you can control the mode of operation of substations equipment, as well as transmit control commands of switches and various functions.
Another function - telephone communication function. The RF channel can be used for operational negotiations between adjacent substations. In modern conditions, this feature is not relevant, as there are more convenient ways of communication between service personnel of objects, but the RF channel can serve as a backup channel of communication in case of an emergency when there is no mobile or wired telephone.
Communication channel over power lines - a channel used to transmit signals in the range from 300 to 500 kHz. Different communication circuits are used. Along with the phase scheme - the Earth (Fig. 1), which occurred most often due to its economy, schemes are applied: phase - phase, phase - two phases, two phases - land, three phases - land, phase - phase of different lines. HF Barrier, communication capacitor and connection filter used in these schemes are the equipment processing equipment for the organization by their wires of RF communication channels.
Fig. 1. Structural diagram of a simple communication channel over the power line between two adjacent substations: 1 - HF barrel; 2 - communication condenser; 3 - attachment filter; 4 - RF cable; 5 - device of the TC; in - telechange sensors; 7-receivers of teleximents; 8 - devices relay sewn or (s) teleavtomatics; 9 - PBX; 10 - PBX subscriber; 11 - Direct subscribers.
Treatment of lines is needed to obtain a stable communication channel. The attenuation of the RF channel via the treated power transmission is almost independent of the lines switching scheme. In the absence of processing, the relationship will be interrupted when it is disconnected or grounded by the ends of the LAM. One of the most important communication problems on power lines is the lack of frequencies due to low transient attenuation between lines having a connection through the substation bus.
RF channels can be used to communicate with operational-exit brigades that carry out the repair of areas of damaged power lines eliminate damage in electrical installations. For this purpose, special portable transceivers use.
The following RF apparatus is used, connected to the treated LPP:
combined equipment for telemechanic channels, automation, relay protection and telephone communication;
specialized equipment for any one of the listed functions;
further communication equipment connected to the LAM through the attachment device directly or using additional blocks to shift the frequency and increase the transfer level;
pulse control equipment for lines.