| High-voltage power lines (HVPL) have long been used in power systems to transmit information at high frequencies (HF). HF communication is constantly evolving and remains the most reliable means of controlling remote objects of electric power systems and an economically advantageous type of communication when transmitting small amounts of information over long distances.
The equipment for high-frequency communication over power lines is, as a rule, a two-way analog transmission system (ATS), in which a high-voltage block for connecting to the power line is additionally installed, and there are also specific terminations for solving control problems, transmitting telemetry signals and inter-machine exchange in power grids.
Digitalization of HF communication systems consists of replacing analog equipment with digital equipment where possible and appropriate. When choosing a strategy for upgrading HF communication systems, a dilemma arises: on one side of the scale is a complete replacement of analog communication equipment with digital, on the other — a partial replacement of analog equipment while preserving that part of it that does not create «bottlenecks» in communication channels and has proven itself well in terms of reliability and ease of operation. In any case, digitalization expands the functionality of the system, increases the transmission speed, simplifies interfacing with a control system built on the basis of computers, a digital communication network, etc. This article discusses the partial replacement of HF communication equipment using the Zelax M-ASP-PG-LEP complex, consisting of a digital modem and a 10-channel multiplexer.
When connecting the M-ASP-PG modem to the 3-channel HF communication equipment (ASK-3 or ABC-3), the analog units for generating a 3-channel signal with one sideband of this equipment are switched off, and a digital signal of the modem, coinciding in spectrum with the group signal of the HF communication equipment, is fed to the input of the frequency conversion and group signal amplification units. In this case, the HF communication equipment becomes digital both in modulation methods and in ports that are given to the consumer, including telephone channels that use digital speech compression. It should be noted that when connecting the complex to the HF communication equipment, the frequency division of the signal transmission directions is preserved.
Using the Zelax M-ASP-PG-LEP complex allows:
1) organize a digital channel with a transmission rate of up to 80 kbps in group paths of high-frequency communication systems; this channel can be used for various purposes, including connection to the Internet, to digital transmission systems, to local networks, etc.;
2) create several (up to six) high-speed telemetry channels (up to 9.6 kbps), which cannot be implemented on old equipment; the possibility of connecting digital sensors operating in continuous monitoring mode is provided;
3) increase the number of telephone channels compared to old equipment (4 channels instead of three).
The proposed upgrade option is especially advantageous for long-distance low-channel HF communication systems, where the use of fiber-optic or radio relay lines is economically inexpedient. Implementation of digitalization of HF communication systems using the Zelax M-ASP-PG-LEP complex allows supporting new and old telemetry systems in one device.
The complex can be controlled using a 4-button keyboard located on the front panel of the device, or from an external terminal, which can be a personal computer or a pocket computer. It is possible to control the complex from a remote device, which makes it possible to remotely configure and diagnose the equipment, which allows increasing the number of unattended and rarely attended substations.
The complex has four FXS/FXO telephone ports (4xFXS or 4xFXO) and 6 RS-232 ports; the RS-232 ports can be programmatically configured either to work with telemetry devices or to perform intermachine exchange functions.
The proposed complex is compatible with the ASC-3 and ABC-3 systems. It is possible to connect the complex to 6- and 12-channel systems when the complex occupies the frequency band of three TF channels while maintaining the standard operating mode of the remaining channels of the system. Design: two metal cases, each 1U high, for mounting in a 19-inch rack. Power: universal –36-72 V or alternating voltage 220 V, 50 Hz. Warranty: 5 years. |
