The hottest fieldbus makes scheduling automatic

Fieldbus enables scheduling to realize automation

fieldbus refers to the digital, serial and multipoint communication data bus between the field device installed in the manufacturing or process area and the automatic device in the control room. It is a kind of industrial data bus, which is the bottom data communication network in the field of automation. Simply put, fieldbus replaces the transmission of traditional mA analog signals and ordinary switching signals with digital communication. It is an all digital, bidirectional and multi station communication system connecting intelligent field equipment and automation system. It mainly solves the digital communication between intelligent instruments, controllers, actuators and other field devices in the industrial field, as well as the information transmission between these field control devices and advanced control systems

system composition

the dispatching automation system based on fieldbus is mainly composed of plant and station end system, dispatching end system and communication system

(1) the monitoring and control system of the station end system

the station end (power plant, substation end) is composed of front-end intelligent unit, industrial computer, network communication management adapter card, special modem modem and corresponding software

1) front end intelligent unit. On the one hand, the front-end intelligent unit can install different clamping rates for each line current (A-phase, B-phase and c-phase), voltage (A-phase, B-phase and c-phase voltage; ab phase voltage; BC phase voltage; CA phase voltage), three-phase/single-phase active power, three-phase/single-phase reactive power, three-phase/single-phase positive reactive power, three-phase/single-phase positive reactive power, three-phase/single-phase negative reactive power Measurement of three-phase/single-phase power factor, cycle and other electrical parameters; On the other hand, it is necessary to complete the detection and control of each switch state. The front-end intelligent unit generally adopts a 16 bit microprocessor system, which mainly includes acquisition and control logic, analog signal processing, switching value input, check whether the operation is normal, output processing, communication processing, system monitoring and protection, real-time clock and power supply. The front-end intelligent unit can work reliably in the harsh electromagnetic environment and can be installed in the outdoor terminal box

2) industrial computer. The industrial control computer is used to display the main electrical wiring and its operation status of the plant and station, record various data, display various curves and charts, alarm and print abnormal or accident, transmit and receive information. Generally, only one industrial computer is needed in the substation to complete all the above work. In power plants, the number of industrial computers can be increased according to the needs of monitoring points

3) network communication management adapter card. The network communication management adapter card is inserted into the expansion slot of the industrial computer, which realizes the high-speed data exchange between the front-end intelligent unit and the industrial computer through the fieldbus, and realizes the management of the network

4)Modem。 Modem (modem) is a special modem of power system, which completes the data communication between power plant, substation and dispatching terminal. (2) The dispatching end system

the dispatching end monitors, controls and manages the whole system. The dispatching end system is composed of industrial computer, modulation and demodulation equipment, multi-channel communication interface equipment and large screen display. The modem receives the modulated signal from the carrier machine, and the command sent by the dispatcher can be modulated by the modem and sent to the carrier channel, and then sent to the station. The multi-channel communication interface completes the data communication between multi-channel digital signals and the industrial control computer at the plant and station end. Large screen display is used to display power network diagram, electrical parameters, load curve, etc

(3) digital communication

the data exchange between the station and the dispatcher is transmitted through the data channel. At present, the power system has carrier channel, microwave channel and optical fiber channel. For the carrier channel and microwave channel, it is necessary to use the special modem of the power system at both ends of the channel. The modems at both ends of the same channel should preferably use the same model of the same manufacturer. Yield strength

system characteristics

the real-time monitoring system of power plants and substations based on Fieldbus and the dispatching automation system formed by it can not only avoid using a large number of cables to transmit the secondary electrical parameters of Pt (potential transformer) and CT (current transformer) to the central control room, but also reduce the error caused by line loss and improve the measurement accuracy. In addition, the central control room can be cancelled to realize unattended. Cellulose derivatives are generally white fibrous, granular or flake, which not only saves the floor area and infrastructure investment, but also frees the operators from the fatigue of day and night duty. Compared with the traditional station monitoring system, the station real-time monitoring system based on Fieldbus has the following characteristics:

1) the front-end intelligent unit (or field intelligent device) can be installed in the CT or PT terminal box to process the collected data locally, and then digitize (through fieldbus) transmission

2) the network consists of two twisted pairs, with low failure rate and high communication baud rate

3) it solves the problem of pressure drop from CT and PT to the central control room in the traditional monitoring system, and the measurement accuracy is high

4) it has strong anti-interference ability and can operate under outdoor harsh conditions

5) simple structure, small volume, convenient installation and maintenance

from the above characteristics of the system, it can be predicted that the monitoring and monitoring system based on Fieldbus will be widely used in power plants and substations of the power system, and it will constitute a new generation of dispatching automation system together with data channel and dispatching end monitoring system