Discussion on the construction of automation front

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Discussion on the construction of county dispatching automation front-end system Abstract: the dispatching automation front-end system is the bridge of scada/ems system, which affects the automatic data transmission. The selection of front-end system directly affects the performance of the whole automation system. This paper discusses the front-end system

key words: channel route switching front-end system power system dispatching automation front-end system is responsible for the tasks of data communication and protocol interpretation with the automation devices of each substation. It is the foundation and bridge of scada/ems system after being transmitted through various channels between the main station and sub station, modulated or demodulated, and intelligently switched to the main station or sub station. However, with the development of communication and network technology, the front-end system technology is developing rapidly, and the universal hardness tester is also used to measure the hardness value under a variety of hardness scales quickly. The construction of the front-end system when the county-level dispatching automation system is upgraded is discussed below. 1. Selection of channel route the selection of substation telecontrol information transmission channel shall be determined according to the existing communication mode and telecontrol transmission protocol mode. The rural power information of our city has been built, and it has gradually changed from a single analog channel (such as carrier wave) or digital channel (such as spread spectrum) in the past to network communication based on fiber-optic technology, with multiple channel transmission modes such as multi-channel 4e/m analog channel, 232 digital channel, 10/100m Ethernet, etc. Selection scheme of channel routing for new substations: at present, new substations are generally equipped with optical fiber channel, and the telecontrol information transmission protocol is mainly 104 protocol. 10/100m Ethernet channel should be selected as the main channel first. Considering that the dispatching real-time control information should meet the secondary safety protection requirements of the power system, the automatic information network transmission channel is not shared with the MIS channel, and the 2m circuit with independent communication is often used in the substation, which is transmitted on the SDH circuit through 10m/2m protocol conversion, and then converted by 2m/10m protocol. At the same time, considering the existing communication mode, 4e/m analog channel or 232 digital channel can be selected as the standby channel to transmit the telecontrol information of CDT or 101 protocol. Selection scheme of channel route of built substation: 48 After tightening the sample, e/m analog channel or 232 digital channel, and the communication rate is 600~1200bit/s. Selection principle of 4e/m analog channel and 232 digital channel: generally, 232 digital signal comes out of the substation communication summary machine first. How to consider selecting 232 digital channel or 4e/m analog channel? The specific situation of the site should be considered when choosing which channel to use. 4e/m analog channel is better than 232 digital channel in transmission distance and anti-interference, but 4e/m analog channel is lower than 232 digital channel in transmission rate, and modulation and demodulation links should be added. If the distance between the telecontrol device and the transmission equipment is far, more than 15m, the electromagnetic interference in the surrounding environment is strong and the amount of information transmitted is not too much, 4e/m analog channel can be selected; If the telecontrol device is close to the transmission equipment, and the transmission equipment has a 232 digital channel interface, 232 digital channel can be selected preferentially; If the telecontrol device is far away from the transmission equipment and requires a 232 digital channel interface, the corresponding long-line drive equipment should be installed on the telecontrol device and transmission equipment side. Shielded cables are required for signal cables. Both ends of the shielding layer should be grounded. Strong current should be avoided during laying, and the cables should be as short as possible. If the communication protocol of the built substation is transformed into 104 communication protocol, then 10/100m Ethernet channel routing can also be considered first. Consideration of standby channel routing of each station. According to the operation management regulations of unattended substation, each station should have two channels with different routing properties. At present, the optical fiber communication in our city has been completed. According to the existing communication network, the county-level dispatching automation data transmission dual channel option: for the stations on the ring communication, if the station optical equipment operates reliably, it can be considered to have dual channel operation. For stations that are not link points or ring stations with unreliable optical equipment, another channel route should be considered. The technology of transmission equipment, such as carrier wave and spread spectrum equipment, which operated before the completion of optical fiber communication, has been relatively mature, and has accumulated rich operating experience, so it should not be out of service at once. If the equipment operates stably, it should be retained, and maintenance should be continued to be strengthened to provide a standby channel for automatic information transmission and enhance the reliability of data transmission of dispatching automation system. 2-channel equipment channel equipment refers to modems, photoelectric isolation boards (or long-line drivers), and switches, which are used to adapt channel signals. Generally, if the channel signal is an analog modulation signal, a modem should be selected; If the channel signal is RS-232 digital signal, photoelectric isolation board shall be selected; If the channel signal is RS-232 digital signal and the signal cable is long, long line driver shall be used and corresponding long line driving equipment shall be installed at the far end. Since the terminal server can only receive asynchronous signals, some channel devices have synchronous/asynchronous conversion devices for receiving synchronous signals. The model of channel equipment shall be determined according to the actual situation of the system and design planning. Now the intelligent channel board has been put into use in large quantities, changing the traditional channel switching mode. The intelligent channel board is actually a programmable modem board, which can be switched between the input main and standby channels through the program control channel board. The front-end processor and the channel control system board use internal protocols to communicate. Its advantage is that it does not need the channel switching cabinet, simplifies the front-end system wiring, improves the system reliability, and reduces the cost at the same time. Dual channel switching automatically switches according to the receiving level and bit error rate. In addition to automatic switching, channel switching should also have the ability of manual switching. 3 front end system switching technology the front end system can realize the multi-channel processing of a plant and station, that is, what we call the multi-channel problem of plant and station communication. It should have different channels, which can be different communication media or different communication protocols, one of which is the main channel and the other is the standby channel. It can easily realize the master-slave switching between 104 protocol and other protocols, and make the switching layer located in the data layer. The front-end system switching can complete the switching selection of the uplink dual channel signal and the downlink signal, and the original data will not be lost during the switching. There are two switching modes for the front-end system switching: the whole machine switching mode: when the switching command is switched to the host, the front-end host is in operation at this time, and the price of products with similar labels at the front-end standby machine can range from $50 to $2000 per kilogram, which is not equal to the hot standby state; When switching the command to the standby machine, the front standby machine is in the running state and the front host is in the hot standby state. The downstream data (TXD) of each channel of the front-end processor in operation status can be used

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