The most commonly used equipment for power communication: distribution frame. If the term is explained by the concept of power system, it is the bus used in communication system. According to different communication modes, it can be divided into audio distribution frame, digital distribution frame and optical distribution frame, which are referred to as VDF, DDF and ODF respectively.
1 distribution frame
Audio distribution frame
As shown in the figure below, this is the audio distribution frame commonly used in stations. Its function is to connect devices that transmit at 64k speed.
The first row of terminals of the whole line shown in the above figure, usually called the equipment side, leads to PCM (which will be introduced later).
As shown in the above figure, the first row of wires with one-to-one correspondence have scattered openings and are connected to the automation equipment in the station. According to the formulation of communication mode, the corresponding terminals are selected. Common equipment at the user end: dispatching and centralized control main and standby equipment, in-station telephone, metering telephone, dispatching direct dial telephone and centralized control direct dial telephone for automation.
Generally, the field work is to transmit all the user equipments in the station to VDF through a network cable or multiple cables, and fill a row of VDFs, and then jump to the corresponding ports through audio cables. In the past, some old stations were hung on the comprehensive distribution cabinet through the terminal board and then jumped. How to connect wires depends on site conditions and operation mode.
Digital distribution frame (DDF)
Although the form is different, it is similar to VDF in essence, and there are also devices and clients. The equipment side usually refers to the optical transceiver, and the user side mainly refers to PCM equipment with services and a small number of dispatching data network routers.
What you can see in the picture is the connection terminal, which connects the upper row and the lower row together, and the two terminals form a complete transceiver channel. On its back, the upper end is a 2M line from the optical transceiver, which is generally fully inserted, and the lower end is connected by selecting appropriate ports according to the formulation of communication working mode, and then a channel is formed together through the connecting terminals shown in the above figure.
Optical fiber distribution frame (ODF)
Compared with the two distribution frames shown above, ODF is much simpler. There is no difference between the device side and the user side. It consists of the core wire separated from the off-site optical cable, which is generally an integer multiple of 12. Common ones are 24 cores and 48 cores. After welding and laying, off-site outlet is provided through flange. Optical terminals and routers can connect the tail fiber core of the outlet to the terminal corresponding to ODF, with one core receiving, one core sending and two cores * * *. From this, it can be judged that a 24-core optical cable can be equipped with 12 optical terminals or routers if it is fully loaded. Where the optical terminals or routers send signals and which core it passes through at which station needs to be adjusted according to the communication operation mode.
The above figure is the ODF diagram commonly used in the station, and the occupied 1 and 2 cores constitute a complete service.
In some cases, some remote stations need to send the signals in the station to the station through the stations interconnected by actual optical cables, and then send them to the local station after repeated transmission. This connection is also called jump connection. For each optical cable, each pair of cores can only run one service at the same time, and the terminals receiving and sending in the station need the same core to receive. This is a point that needs to be remembered when conducting optical transmission communication.
2 Main communication equipment
pcm
In optical fiber communication system, binary optical pulse "0" code and "1" code are transmitted in optical fiber, which are generated by switching modulation of light source by binary digital signal. Digital signals are generated by sampling, quantizing and coding continuously changing analog signals, which is called PCM (pulse code modulation), that is, pulse code modulation. This electrical digital signal is called digital baseband signal, which is generated by PCM electrical terminal. PCM has two standards (expression forms), namely E 1 and T 1. China adopts the European E 1 standard. The rate of T 1 is 1.544Mbit/s, and the rate of E 1 is 2.048 mbit/s. ..
Through the above introduction, it is not difficult to see that PCM actually realizes the mutual conversion between 64k audio transmission and 2M digital transmission, and completes communication through one-to-one correspondence of time slots. A 2M direction can be divided into 32 time slots, of which 0 and 16 time slots are dedicated to equipment and cannot be used for service transmission. The remaining 30 time slots can be used for voice service and service transmission of automation equipment. Specifically adjust the service time, according to the requirements of the equipment, use the handheld terminal that comes with the equipment or connect it to the computer through a special serial line for adjustment.
In short, the function of PCM in communication is to convert the automation equipment signals and voice signals in the station into 2M signals, which are connected to SDH transmission equipment through a pair of 2M transceiver lines and DDF. The common maintenance operation is to modify the time period by logging in the equipment according to the formulation of the mode, thus changing the business direction.
PCM is like this, and it is made by different equipment manufacturers.
optical transmission equipment
Optical transceiver is convenient for our internal use, and its official name is SDH optical transmission equipment. SDH optical transmission equipment is an integrated information transmission network integrating multiplexing, line transmission and switching functions, and is operated by a unified network management system. SDH optical transmission equipment can realize effective network management, real-time service monitoring, dynamic network maintenance, interoperability between different manufacturers' equipment and other functions. Because of its good compatibility and advanced transmission mode, it is a hot spot in the development and application of transmission technology in the information field in the world today, and occupies a major position in the communication optical transmission network. Under the current application background, the maximum bandwidth capacity of a single optical path is 2.5G, which is very common in hub station transmission. Of course, at the provincial level, the bandwidth capacity may be as high as 10G.
In practical application, SDH optical transmission equipment gathers all 2M signals in the station into optical transmission signals from DDF side, which are connected to ODF through pigtails and transmitted outside the station. The common maintenance operation is to adjust the light path on the network management, and it is necessary to clean the fan baffle in time when patrolling the station, otherwise it will easily lead to excessive temperature and abnormality.
Common optical transmission equipment is so long. A large bundle of wires on the upper layer is 2M wires, which go to DDF, and a large number of yellow optical fibers on the lower layer are pigtails, which are connected to ODF terminals.
Switches and routers
The role of router in power communication is similar to that of optical transmission equipment, which is generally the exit equipment in the station, that is, all services are connected to the router in the form of network cable, and then the router reaches the local end through a specific route. It can be said that it is in the same position or even a higher position. It can support a variety of protocols, and the provided GE port can be connected to both optical cable pigtails and network cables, with better compatibility. Moreover, the transmission mode is much simpler than the combination of PCM and optical transmission, which reduces many intermediate nodes and is convenient for maintenance personnel to locate the fault point more accurately. Of course, its disadvantages are: when the optical path fails, it is not as fast as SDH equipment to switch channels, and it takes some time to calculate the backup route; And all services need to be connected to the router in the form of network cable. At present, in the old station, the telephone service does not support network cable. At present, the D5000 system used in power system is transmitted through a dispatching data network composed of routers, and the D5000 devices in the station are connected to the routers in the form of network cables.
The above picture is a schematic diagram of the switches and routers in the station. The first two devices of many network ports are switches, which are responsible for gathering all network cable access services and then transmitting them to the router on the fourth floor. The router is connected with ODF through tail fiber, and transmits all signals out of the base station.
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