【導(dǎo)讀】穩(wěn)定運(yùn)行具有極其重要的作用。本畢業(yè)設(shè)計以實(shí)驗(yàn)室現(xiàn)有設(shè)備為基礎(chǔ)，對基于PLC. 的變電站綜合自動化系統(tǒng)進(jìn)行研究?；瘜?shí)際系統(tǒng)進(jìn)行初步的硬件結(jié)構(gòu)設(shè)計和軟件設(shè)計。并以斷路器控制、中央信號系。央信號系統(tǒng)的基本功能。SIMATICS7-200PLC系統(tǒng)的基本組成及其工作模式………………………

　　

【正文】 amples are under frequency load shedding and bus automatic transfer. To summarize, the main features of a substation system are: Buses, lines, transformers and VAR devices are the basic equipment in a substation. They function together to transfer and distribute power. Requirements for the monitoring and control of buses, lines, transformers and VAR devices differ from each other. A large amount of data in a substation is from switchgear bays, a small data to them. Protection and measurement for monitoring have the same data source but different requirements for sampling frequency and control algorithms. Relay protection is a fundamental function and its normal operation should be ensured even if other devices fail to work. There is little information exchange between switchgear bays. The control of a circuit breaker in switchgear bays may have various causes such as line faults, loss of system synchronism, equipment over loading, under frequency load shedding, normal work operations and so on. 鄭州大學(xué)電氣工程學(xué)院畢業(yè)設(shè)計（論文） 32 Whatever the cause is, the operation is the control of circuit breakers. Transformers and VAR devices have two kinds of control, ., control in fault conditions and in normal system operations. Based on the above analysis and from the point of view of monitoring, control and management of power transfer and distribution in substations, this paper proposes that a substation consists of such BCs as buses, lines, transformers, VAR equipment and so on. A BC provides data through one or several switchgear bays to and receives control mands from the secondary system. Each BC has its own characteristics and requirements for monitoring and control. Thus a BC in a substation can be treated as a basic research object of monitoring and control. The set of all basic research objects, managed, coordinated and controlled by the substation main puter, forms an ISA system. The hardware structure of a BC is noted as IED. According to the functional requirements of a BC, IED is designed by the fault independent rule and function independent rule. Each BC has its corresponding IED which mainly differs in I/O interfaces from that of another BC. For example, the transformer IED not only interfaces with temperature and pressure transducers, but also has a larger number of I/O than a line IED has. It must control all the breakers on the side of each winding under fault conditions and control the onload tapchanger under normal operations. The IED of a VAR device or a line BC provides a serial port to municate with a intelligent VAR device, or the protection device located on the other side of a line. A typical IED hardware structure of a BC is shown in . The AC/DC sampling and Binary I/O parts are connected to a bay through PT/CT and optical insulators, acquiring data from the bay and controlling the breaker. The Process and Control part analyzes, calculates and processes the acquired data, and performs protection functions by tripping the breaker if faults are detected. Through ***：基于 PLC 的變電站綜合自動化系統(tǒng)研究 33 Fieldbus interface, an IED municates with the substation puter system (SCS) or other IED. It transmits real time data to the SCS for supervision and receives mands from SCS or other IED for control. MMI is used for displaying the acquired data and parameters, testing and maintenance of the IED. The bus IED acquires directly the current and status data from the bays and detects bus faults. If a fault is detected, all breakers of all units connecting the bus are tripped by the bus IED. The function of under frequency load shedding is realized by the bus and line IED, coordinated by the SCS. 3. Information Exchange and Field Bus The munication interface between the current lED of ISA is mainly by RS422/485 series port and only a few is by local area work (LAN). Using RS422/485 munication interface, the link among nodes can be done, but the number of nodes linked cannot be more than 32 and can not suit the future demands of ISA. In addition, the munication mode is master/slave and has drawback as follows: Only one node is the master, and the others are slaves in the munication . If the master node is at fault, the system will immediately fail. The munication mode of master/slave structure is unbalanced. The slave responds to the mands from the master and sends data to the master. The efficiency of data transmission is low and important data in the slave can not be transmitted immediately until it receives the mand from the master. The larger the system scale, the lower the realtime of system performance. The master/slave munication mode can not meet the requirements of munication between any two nodes. Using RS422/485 series port interface, it is easy to connect each other. But the protocol among the IED is different and no standard in China is followed. Therefore, the munication control is plicated and it is difficult to realize highspeed, reliable and accurate information exchange between IED. The media for munication is limited and systems engineers are occupied with programming and testing munication software. Applying LAN technology, the data can be transmitted in high speed and the functions of central processing can be distributed to nodes for processing. But in the field of process control, the advantages of LAN are less obvious owing to the following reasons: In the LAN, a large quantity of data is transmitted in a package of message, but they are not frequently transmitted. In general the rate of munication in LAN is higher, l0 Mbps. In contrast with LAN, process control work must frequently transmit a small quantity of data. When the work is sustained with heavy load due to message collisions and retransmissions, its efficiency of transmitting data will be degrad