Power Line Carrier (PLC) Communications
Working documentation: from 22 days
Price from 50000 roubles
We design RF communication systems and high-frequency communication lines, ensuring stable signal transmission, high noise immunity and reliable communication operation in difficult operating conditions.
We design HF communication systems for industrial, energy and infrastructure facilities. We develop a project for high-frequency communication lines, including equipment selection, line routing and calculation of signal transmission parameters. Well-designed high-frequency communication lines provide stable and reliable communication under conditions of increased requirements for communication quality.
Why is the HF channel, calculated without taking into account the real parameters of the power line, unreliable from day one?
High-frequency communication over power lines is a highly specialized technology, where an error in the choice of carrier frequency or incorrect calculation of channel attenuation means not just poor communication, but a potential failure of the relay protection system at the time of a short circuit. A power line as a signal transmission medium behaves fundamentally differently than a cable or radio broadcast: the level of interference on it depends on the operating mode of the power system, the number and type of connections, the parameters of lightning protection cables and the grounding scheme. A project written without calculating the path attenuation for a specific OHL configuration and specific equipment is a project with an unknown signal level margin. When this margin turns out to be negative, the protection does not work.
AYU-Project designs high-frequency communication lines over overhead power lines 35-750 kV for power generation facilities, oil and gas and mining industries. We develop design documentation and working documentation based on the calculation of the HF channel with a confirmed signal level margin - so that the channels of relay protection, emergency automation and technological communication work with design characteristics for the entire life of the facility.
What is HF communication over power lines and where is it used?
HF-power line communication is a technology of using phase conductors and lightning protection cables of overhead lines as a guiding medium for transmitting high-frequency signals in the 16-1000 kHz range in parallel with operating power frequency alternating current. The signal is introduced into and removed from OHL through specialized connection equipment, which provides electrical isolation of the low-frequency (50 Hz, high-voltage) and high-frequency paths.
This is the only communication technology that does not require laying a separate communication line between substations: the HF channel exists exactly where the power line already runs. That is why it remains indispensable for:
- relay protection channels (RPA) - differential-phase protection of lines (DPZ), directional protection, intersystem protection channels: a minimum command delivery time is required (units of milliseconds) with guaranteed reliability;
- emergency automation (PA) - transmission of commands for automatic frequency unloading (automatic underfrequency load shedding), automatic restart (automatic reclosing), automatic elimination of asynchronous operation (ALAKh);
- technological telephone dispatch communication - operational negotiations between dispatchers over a line that does not depend on the state of terrestrial or cellular networks;
- telemechanics - transmission of telemetry and remote-control signals from substation equipment to the control centre;
- ASKUE - commercial metering of electricity with the transfer of meter readings to the automated control system;
- technological video surveillance - broadcasting a video stream from remote objects in the absence of other communication channels.
Composition of equipment for connecting the HF channel
The interconnection equipment is the physical interface between the high frequency channel and the power line, operating at full line voltage. The composition and parameters of the connection elements are determined by calculation and cannot be chosen arbitrarily.
HF-minelayer (line trap) - an inductive filter connected to the phase wire break directly at the substation. Its function is to create high resistance for HF signals towards the substation busbars (where they would be bypassed), without preventing the flow of power frequency operating current. The type and inductance of line trap are selected based on the rated operating current of OHL and the required stop band. Installed on the open switchgear (outdoor switchgear) of the substation.
coupling capacitor - a high-voltage capacitor through which the HF signal is introduced into the phase wire. The operating voltage of the capacitor corresponds to the voltage class OHL (35, 110, 220, 500, 750 kV). The capacitor passes the HF signal, but presents a high resistance to power frequency current, thereby providing galvanic isolation of the HF equipment from the high voltage part.
Connection filter - a matching transformer unit connecting the coupling capacitor to the coaxial cable leading to the HF equipment on the relay panel rack. The filter matches the characteristic impedance of the line (240-450 Ohm for overhead OHL) with the characteristic impedance of the coaxial cable (75 Ohm) and additionally filters low-frequency components. Configured to the operating frequency band of a specific HF channel.
How is the HF channel calculated?
Calculation of the HF channel is a mandatory engineering procedure, the result of which is confirmation of the channel’s operability under the worst conditions: maximum signal attenuation in the path, minimum margin in reception level. Without this calculation, it is impossible to select the carrier frequency or select the equipment.
Carrier frequency selection - the most critical stage. The frequency is selected from the range 16-500 kHz (for most applications) taking into account several conditions simultaneously: the absence of intersection with already assigned channels of adjacent overhead lines in a given power system node; minimum attenuation in the path at a given frequency; compliance with the type of equipment (narrowband or broadband). For relay protection and PA channels, frequencies that provide minimum command delivery time are preferred.
Calculation of attenuation of the HF path includes: attenuation in the wave impedance of the overhead line at the carrier frequency, taking into account the type of wire, span length and voltage class; attenuation in coupling capacitors and connection filters; attenuation on branches and shunting action of elements connected to the buses; the total attenuation in the path from the transmitter of one substation to the receiver at another.
Calculation of signal level margin - comparison of the signal level at the receiver input with the sensitivity of the receiver and the level of interference. The standard margin for relay protection channels is no less than 8-10 dB; for technological communication and telemechanics channels - not less than 6 dB. Insufficient margin is detected at the DD stage and is eliminated by changing the carrier frequency or transmitter power.
Checking compatibility with adjacent channels - analysis of the frequency plan of an adjacent node to eliminate mutual interference between HF channels of different OHL connected to the common substation buses.
Connection diagrams to OHL: phase-to-ground and phase-to-phase
The choice of connection scheme to the phase wires OHL fundamentally affects the attenuation and noise immunity of the channel. This is the first technical parameter determined at the beginning of the design.
Phase - ground circuit - HF-signal is input into one phase wire, the return conductor is ground and neutral. Easier to implement (one coupling capacitor and one line trap), but more sensitive to line asymmetry and ground noise. Used at OHL 110 kV and higher, provided there is sufficient signal level margin.
Phase-phase diagram - the signal is introduced between two phase wires; requires two coupling capacitors and two VChZ, but provides significantly lower attenuation and better noise immunity. Preferable for long lines, lines with branches and relay protection channels with strict reliability requirements.
Scheme for lightning protection cable - used on OHL with cables isolated from supports; allows you to organize a HF channel regardless of the operating mode of the phase wires. Used for special tasks when normal operation of phase channels cannot be guaranteed.
The choice of connection scheme is recorded in DD and determines the composition and cost of the equipment, as well as the complexity of installation at the outdoor switchgear substation.
What is included in design documentation and working documentation?
Documentation is developed in accordance with Government Decree of the Russian Federation No. 87 dated 16.02.2008 No. 87 (as amended on 21.10.2025) “On the composition of sections of project documentation and requirements for their content”, WD 34.48.404-96, WITH 34.35.311-2004, as well as standards of organizations (STO) network companies PJSC Rosseti and FGC UES when designing for facilities in their area of responsibility.
Design documentation stage includes:
- an explanatory note describing the design decisions taken;
- diagram of the organization of HF communication indicating the types of channels (RPA, PA, dispatch communications, telemechanics, AMR) and their carrier frequencies;
- results of calculation of the HF channel with confirmation of the standard signal level margin;
- justification for choosing the type of connection equipment and RF equipment.
Working Documentation Stage (WD) contains:
- RF communication organization diagram with details for each channel and each substation;
- drawings for installing HF barriers on outdoor switchgear with reference to the design of the portals and the busbar;
- installation drawings of coupling capacitors and connection filters;
- connection diagram of HF equipment on the relay panel with coaxial cable tracing;
- external connection diagrams: coaxial path from the connection filter to the equipment in the control room/control panel building;
- equipment layout plan on the HF equipment rack (cabinet);
- power supply circuit for HF equipment with power supply from DC buses (110 V or 220 V DC) and redundancy;
- cable log and connection tables;
- specifications of equipment and materials;
- statement of quantities.
Regulatory basis for designing HF-connection
- WD 34.48.404-96 “Guidance document for the design of PLC communications along power lines” - a fundamental regulatory document of the industry: methodology for calculating HF-channels, requirements for connection equipment;
- WITH 34.35.311-2004 “Guidelines for determining the parameters of a high-frequency path” - calculation of attenuation, connection diagrams, influence of parameters OHL;
- STO 56947007-33.060.40.134-2012 “Typical technical solutions for PLC communication systems” - standard FGC UES / Rosseti; used when designing UNPG facilities;
- IEC 60353 "Line traps for a.c. power systems" - international standard for HF suppressors;
- IEC 60481 “Coupling devices for power line carrier systems” - international standard for connection equipment;
- GOST R 21.1101-2020 - requirements for working documentation (WD) formatting;
- Government Decree of the Russian Federation No. 87 dated 16.02.2008 No. 87 (as amended on 21.10.2025) “On the composition of sections of project documentation and requirements for their content.”
Pricing and how to order
The cost of developing design documentation and working documentation is determined by the number of HF channels, voltage class of overhead lines, number of substations and types of channels (relay protection, PA, dispatch communications, telemechanics). Approximate calculation - through the online calculator on the website.
How to order the design of HF-communication along power lines?
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Submit an enquiry - the consultation is free
Form on the website or phone: +7 (383) 375-73-77 / +7 (923) 743-73-77. Indicate the object (type and voltage class of the overhead line, number of substations), the composition of the planned HF channels and the available initial data. -
Receive a Commercial Proposal Within 1 Business Day
CP with scope of work, cost and timing. The cost depends on the number of HF channels, the voltage class of the overhead line and the types of channels (relay protection, PA, dispatch communications, telemechanics). -
Analysis of initial data and signing of an agreement
Checking the completeness of source materials: single-line diagram OHL, diagram hydroelectric power plant substations, frequency plan of the node (for objects UNPG). If necessary, request missing data. Signing the contract. -
Calculation of HF channel
Selecting the carrier frequency (16-500 kHz) with checking the frequency plan of the adjacent node. Calculation of path attenuation and signal level margin (≥ 8-10 dB for RPA/PA, ≥ 6 dB for telemechanics). Selection of connection diagram and equipment type. -
Carrier frequency matching (if necessary)
For objects UNPG - preparation of materials for PJSC Rosseti / FGC UES: justification of the selected frequency and checking compatibility with neighboring channels. Support until approval is received. -
Design Documentation (DD) Development
Set for Government Decree of the Russian Federation No. 87 (as amended on 21.10.2025) and WD 34.48.404-96: explanatory note with the results of calculation of the HF channel, diagram of the organization of HF communication, justification of the equipment. Support through the examination is free. -
Preparation of Working Documentation (WD) and Delivery to the Client
Drawings of installation of high-frequency protection and coupling capacitors on the outdoor switchgear, diagram of the coaxial path, plan of RF equipment on the relay panel, power supply diagram (110/220 V DC), cable log, specifications, bill of quantities.
To receive an accurate commercial proposal, leave a request: indicate the object (type and voltage class OHL, number of substations), the composition of the planned HF channels and the available initial data. The initial consultation is free, and we work across Russia remotely.
Our Advantages
How We Work
Frequently Asked Questions
The HF communication project is included in the “Communication Systems” section of the DD for the construction or reconstruction of a substation. If the substation is a capital construction project and falls under the requirements of Government Decree of the Russian Federation No. 87, state expert review of DD is mandatory. When carrying out work to modernize HF equipment at an existing substation without changing the technical characteristics of the facility, expertise may not be required - this issue is clarified at the stage of pre-design analysis. We accompany the project through examination; We will correct comments free of charge.
Minimum required set: single-line VL diagram indicating the voltage class (35-750 kV), line length, type and brand of wire, presence of lightning protection cables and cable grounding diagram; diagram of the main electrical connections of substations with a list of connections on the busbars; composition of the planned VCh channels (RZA, PA, dispatch communications, telemechanics, ASKUE) and reliability requirements; for ENES facilities - the existing frequency plan of the node. If some of the data is missing, our specialists will help determine the composition of the necessary starting materials during a free consultation.
For one HF channel on one overhead line (two substations, one type of channel) - 2-3 DD weeks and 3-4 WD weeks. For facilities with several overhead lines and multi-channel circuits, the deadlines are determined individually. The timing of carrier frequency approvals in network companies is determined by their regulations. All terms are fixed in the contract.
Yes, it is standard practice that a single carrier frequency (or a pair of frequencies in full duplex mode) can be used to simultaneously transmit RZA commands (in a dedicated frequency subchannel), voice dispatch communications (tone subchannels) and telecontrol/ASKUE data. This is called VCh channel multiplexing. Modern digital VCh communication equipment provides transmission of several information streams in one frequency band with priority service for RZA and PA commands.
The connection equipment is designed to operate in open air conditions, under full operating voltage VL and exposed to climatic factors. If the installation complies with the requirements of the manufacturer and periodic tests are performed, the scheduled service life is 30 years or more. Design on equipment corresponding to STO 56947007-33.060.40.125-2012 and IEC 60353/60481 guarantees not only the design parameters of the path, but also the durability of the structure.
Yes. Carrier frequencies of VCh channels over LEP in the Russian Federation are assigned and agreed upon in the manner established by the network company (PAO Rosseti / FSK for ENES facilities) and regional dispatch centers. The VCh channel calculation performed by us includes a justification for the selected carrier frequency with a check for compatibility with neighboring channels - these materials are the basis for the coordination.
On cable lines, the organization of traditional HF channels is much more complicated: the coaxial design of the cable line creates high attenuation for HF signals, and standard connection filters designed for overhead lines with characteristic impedance 240-450 Ohm do not fit well with the cable line. For cable lines, as a rule, fiber-optic lines or other data transmission technologies are preferred. If the client sets the task of organizing an HF channel via CL, we perform a preliminary calculation of attenuation and give an engineering opinion on the feasibility.
The HF channel over power lines is the only type of communication that physically exists where there is a power line, without the need to lay a separate cable. For differential protection channels of overhead lines, the HF channel is often a priority or backup in relation to the fiber-optic line: if the overhead line itself is damaged, when the optics in the lightning protection cable burn out or break, the HF channel along the surviving phase or lightning cable can remain operational. In addition, for long overhead lines in hard-to-reach areas, HF communications have historically been the most cost-effective solution.
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