【 Weak current College 】 automatic meter reading systems theory and its applications

Automatic meter reading systems theory and its applications
Summary: automatic meter reading system is mainly composed of watt-hour, collector, concentrator, data transmission channel, main station system, through the network also can and power supply Bureau business charge system for meter reading fees integration keywords: automatic meter reading system 1, automatic meter reading system of automatic meter reading system is mainly composed of watt-hour, collector, concentrator, data transmission channel, main station system, through the network also can and power supply Bureau business charge fees for meter reading system integration. As shown in Figure 1.
Energy meter-meter has a pulse meter and two mechanical energy meter, pulse meter can output standard pulse signal to the collector, and the mechanical energy meter electricity consumption of the users through the optical or magnetic means converted to standard pulse signal. Collector (or known as acquisition module)--collector is divided into single table collector and multi-table collector, both single table collector can only collect, store, 1 block meter data, multi-table collector may also collect, store, 8, 12, 16, 24, 32 or 64 block meter data acquisition device in addition to the complete meter power data acquisition outside of work, but also according to the system requirements for complete and centralized data communication between, you will need to transfer power data sent to the concentrator. Concentrator-concentrator has two main tasks are completed and collector of data communication, data acquisition device to grant power to freeze command timing cycle receives the power data acquisition system, or system requirements receive a meter or a group of meter data. Another task is based on the system requirements for complete communication with the main station, the user data for electricity, the main station information delivered to the master database. Communication channel-uplink channel: refers to the concentrator and communication between the main station, you can use the telephone line, wireless, green, and so on communication media; the downlink channel: refers to the concentrator and collector of communication lines between mainly 485 bus, power line carrier communication modes of two. Main station system--timing or readily copied residents or businesses meters of electric energy data concentrator set communication parameters and operating parameters and power electricity trading network, you can conduct electricity calculation, ticket printing, statistical reports, electricity charges paid. 2485 bus automatic meter reading system 485 way of reading system is mainly composed of watt-hour, collector, concentrator, data channel as well as the master computer. Which collector is responsible for several meters electricity data set is processed, and packaged up and delivered. Several acquisition via twisted pair and concentrator connected to form a 485 network. Centralized/forwarder responsible and main computer and collector to communicate it to the main computer communication optional telephone line, radio, mini cable etc. (1) single-485 meter reading system: the system from the main station, channel, concentrator, collector and power meter. Primary channels (ascending) generally use the public telephone network (PSTN), concentrators and collector (downlink) adopted between the STP, the communication method for 485, collector and energy meter with a general wire connection for pulse acquisition. The system is suitable for the urban residents of the community and more intensive commercial and residential building, and meter installed in a centralized list box. Each cell in the installation of a collector, you can capture set table inside of all energy meter pulse. For Community internal small business users and units, can lay pulse line to the nearest floor unit collector, if more than 100m, should separate the installation of a collector. About 30 ~ 50 collectors need to configure a concentrator, 485 network cable length should not exceed 1200m. Single-485 meter reading system advantages: ① technology simple, mature, simple to implement; the meter without modification; bus transfer rate is high, and high reliability. ② by using the appropriate channel coding technology, reasonable arrangement of the network cable, you can make the copied rate and data availability achieved two 100%. ③ because many block table set copied way reduces the cost per household, while also reducing the cost of the entire system. Single-485 meter reading system weaknesses: ① construction wiring workload, the network cable is vulnerable to disruption. ② circuit damage, not easy to find the point of failure. ③ easy struck by lightning and overvoltage. Single-485 meter reading system applications: the system for residential and more intensive commercial and residential building, and meter installed in a centralized list box. (2) double-485 meter reading system: the system from the main station, channel, concentrator, collector, 485 module and power meter. Primary channels (ascending) generally use the public telephone network (PSTN), concentrators and acquisition between (downlink) use shielded twisted pair (485), acquisition and use of electrical energy between tables, the STP (485), for collecting energy meter data. This product applies in the city more decentralized commercial and residential users, each meter installation built-in 485 module, the module will Watt-hour meter pulse is converted to the data, and then by 485 interface deliver to the collector. Meter of 485 length cannot exceed 1200m. The system with double-485 bus structure, therefore high data transfer rate, high reliability, because the energy meter with built-in 485 conversion modules, pulse transmission more reliable. Weaknesses remain the construction of wiring workload, the network cable is vulnerable to disruption. 3. carrier meter reading system (1) low-voltage power line basic transmission characteristics and communication technology: simply put, the influence of power line carrier transmission quality mainly on two factors: one is the power network impedance characteristics and attenuation, the other is a noise interference. The first factor constraining signal transmission distance, the second factor which determines the quality of data transmission. Low-voltage transmission network for noise interference is mainly composed of distribution transformers and user devices. The basic sources of noise are: universal AC, DC-motor with SCR in dimming, television receivers, etc. These devices produce background noise include: the random noise, smooth spectrum noise and frequency harmonic noise, etc. Above you can see that the carrier transmission system environmentIs very bad, so you should take some steps to eliminate noise, especially the pulse noise effect on transmission of data. Up to now, the domestic manufacturers of carrier acquisition module mostly based on FSK modulation techniques, some manufacturers are using spread spectrum technology. Relative to using spread spectrum technology module, based on FSK modulation acquisition module has the advantage of lower cost, implementation easier, but its disadvantage is relatively obvious that noise interference and resistance are relatively harmonic capabilities. For using spread spectrum technology acquisition module, as the use of a broadband transmission characteristics of spread spectrum technology, making the system in terms of anti-interference ability has been significantly improved, making the reading system reliability is the degree of improvement. Practice has proved, in order to meet the different grid structure, different neighbourhoods, as well as different time dramatic changes to the actual requirements of the load, whether FSK modulation, or spread-spectrum modulation of power line carrier systems are required for specific situations, relay or with high power (in the permit) and other measures to extend transmission distance and increases transmission reliability for 24/7 reliable meter data copied. (2) single-table carrier module carrier meter reading system: single-table carrier module carrier meter reading systems that are installed in each table of a carrier wave acquisition module, each acquisition module complete power calculation of data acquisition, and low-voltage power line and is located in the transformer Deputy side of centralized/forwarder for communication. System from the main station, channel
Concentrator, carrier, carrier Watt-hour.
Primary channels (ascending) generally use the public telephone network (PSTN), concentrators and between carrier Watt-hour (downlink) use low voltage power line carrier. The carrier Watt-hour is loaded by the meter wave modules. Its main benefits: take full advantage of the power line resources without rewiring, advanced technology, the meter reading technology direction of development. The main drawback: ① RF carrier signals can only be used in a single zone transfer, the transfer cannot be cross-platform area, required with other signal communication means will meter data from concentrator to meter copied Center or business center. ② as the medium-voltage power line itself, the impact of structural and load, the carrier signal is susceptible to interference, 24 x 7 meter reliable copied more difficult, required by a relay or other technical means to solve them. ③ as single table module size and cost, makes software and hardware, it is hard to further improve the reliability and stability of the module, this has to a certain extent, the impact on system performance. (3) the "many table a collector" carrier metering mode: "many table a collector" carrier meter reading is similar to the way 485 meter reading, more energy meter with a collector. The only difference is the acquisition Terminal (module) and set for communication instead of 485 twisted pair, but through the realization of low-voltage power line carrier communication. 4, other special automatic meter reading system (1) the UNB (UNB) carrier meter reading system (cross-platform area single table carrier): the system is suitable for dispersion of urban and rural residents users and industrial users of meter reading, especially for the rural distribution transformer meter, cross-platform area copied. Technical characteristics of the system: UNB technology transfer bandwidth only 0.001Hz, transmit power simply 0.3mW, carrier unit can be directly installed in the power meter, each carrier unit programmatically assign a different frequency, multiple carrier unit (now can add 2880) and is located on the receiver at the substation communication, communication distances, up to 200km. Due to the use of extremely low frequency (5 ~ 9.5Hz) for signal transmission, signal penetrability, transformers, circuit and capacitors, without attaching any gain device, are not subject to interference from other equipment, nor does it interfere with the normal operation of other devices. But because of the UNB modulation techniques, data transfer rate is relatively low and needs to transfer a data member, delivered a complete 33min power data needs to be poor, real-time 16h. For meter reading system, if we can put up with the system of delayed (a complete packet transfer requires more than a dozen hours), then for the Super narrow band transmission systems with very high transmission reliability and strong penetration, can think that this system is the use of utility meter reading system that should cause us to pay attention to. (2) IR meter reading system: the system from the main station, the infrared Palm, collector and power meter, acquisition completed the leather a table box all electricity meters in the acquisition of power, no concentrator or communication lines, meter reading, by staff to the scene, with Palm copied collector storage of meter data, and then return to the main station, the Palm has been copied by meter data via RS232 port, transfer to the main station and the computer. The system due to save a concentrator and 485 wiring, construction cost dramatically lower, the disadvantage is that you want people to the site, the degree of automation. Ideal for a city or rural area of watt-hour meter has been centralized residents. (3) distribution transformer-reading system: the system from the main station, channel, meter reading terminal and distribution transformer total table. This system is mainly for distribution transformers total table of copied electric energy. Meter-reading terminal can direct acquisition meter pulse signal can also be copied multi-function Watt-hour meter data, and through communication lines and equipment will be copied data transfer to the main station. Channel generally use the public telephone network (PSTN), or other communication channels such as radio, fiber, carrier, etc. (4) the frequency meter reading system frequency meter reading system similar to UNB meter-reading system, but its use is carried out through zero-cross frequency modulation carrier communication technology compared with UNB meter reading systems, vulnerable to the effects of harmonic to interference, and require a larger injection power, but transfer rate than the UNB meter reading system.