This paper briefly introduces the importance and development trend of substation integrated automation system, puts forward the basic concept of substation integrated automation, and analyzes the system structure, communication mode, realizable basic functions and development prospect of substation automation.
Keywords: structure and function of substation integrated automation system
I. Overview
Power grid is an inseparable whole. Comprehensive utilization of primary and secondary equipment information of the whole power grid is of great significance to ensure the safe and stable operation of the power grid. Substation integrated automation is a measure to improve the safe, reliable and stable operation level of substations, reduce the operation and maintenance costs, improve economic benefits and provide users with high-quality power services. With the rapid development of automation technology, communication technology, computer and network technology, on the one hand, it has become an inevitable trend for integrated automation system to replace or update the traditional substation secondary system. On the other hand, protection itself also needs more robust functions, such as self-inspection, fault recording, event recording, operation monitoring and control management. Developing and perfecting substation integrated automation system is a new trend of power system development.
Second, the system structure
At present, judging from the development of substation integrated automation at home and abroad, there are roughly the following structures:
1. Distributed system structure
Connecting a plurality of computer single-function devices distributed according to monitoring objects or system functions of a substation to a network that can share resources to realize distributed processing. The biggest feature of the system structure is that the functions of substation automation system are distributed to multiple computers to complete. Generally, the distributed mode is designed according to the function, and the master-slave CPU system is adopted. Multi-CPU system improves the ability to handle parallel and multi-events, and solves the bottleneck problem of CPU operation processing. The data communication between functional modules (usually multiple CPU's) is realized by network technology or serial mode, and the network system with priority is selected to solve the bottleneck problem of data transmission and improve the real-time performance of the system. The distributed structure is convenient for system expansion and maintenance, and local faults do not affect the normal operation of other modules. In terms of installation, this method can form two kinds of system configuration structures: centralized screen assembly or hierarchical screen assembly, which are mostly used in medium and low voltage substations. Since the advent of distributed substation integrated automation system, it has shown great vitality. At present, there are still some problems in anti-electromagnetic interference, information transmission mode and reliability guarantee.
2. Centralized system structure
Generally, a powerful centralized computer is adopted and its I/O interface is expanded to collect, calculate and process the analog and quantity information of the substation in a centralized way, so as to complete the functions of microcomputer monitoring, microcomputer protection and automatic control respectively. The front-end computer completes the functions of data input and output, protection, control and monitoring, and the background computer completes the functions of data processing, display, printing and remote communication. At present, many domestic manufacturers still belong to this structure, which has the following shortcomings:
(1) Front-end managers have heavy tasks and many leaders, which reduces the reliability of the whole system. If the front-end manager fails, all local and remote information and functions will be lost.
(2) The software is complex, the modification workload is heavy, and the system debugging is tedious.
(3) The configuration is not flexible. For substations with different main wiring or different scales, the software and hardware must be designed separately, which has a heavy workload and makes it difficult to expand some functions required by automation.
3. Hierarchical and distributed structure
According to the control level and object of substation, a two-layer distributed control system structure is set up, which is the whole station control level-substation level (station level measurement and control unit) and the local unit control level-interval level (interval unit). It can also be divided into three layers, namely, substation layer, communication layer and interval layer.
Compared with centralized processing system, this structure has the following obvious advantages:
(1) reliability is improved. Any part of equipment failure only affects local areas, that is, "dangerous" dispersion. When the station-level system or network fails, it only affects the monitoring part, and the most important protection and control functions can still continue to run at the section level; The damage of any segment-level intelligent unit should not cause the communication interruption of the whole station, such as occupying the communication network of the whole station for a long time.
(2) High expansibility and openness, which is beneficial to engineering design and application.
(3) The cables required for secondary equipment in the station are greatly reduced, which saves investment and simplifies debugging and maintenance.
Third, common communication methods
At present, Ethernet communication is widely used in China. Before the emergence of Ethernet, neither RS-232C nor EIA-422/485 could avoid the shortcomings of complex communication system and slow communication speed. The application of Fieldbus has alleviated the communication demand of the mobile power station automation system to a certain extent, but it is still stretched when the system capacity is large. The application of Ethernet solves the communication problem. Common communication methods are:
1) dual Ethernet dual monitoring mode, mainly used for 220-500kV transformers. It can be realized in dual controller+dual server mode and supports optical/electrical Ethernet.
2) Single Ethernet, dual/single monitor mode.
3) Dual LON network and dual display mode.
4) Single LON network, dual/single display mode.
Four, substation automation system should be able to realize the function.
1. Microcomputer protection: it protects all electrical equipment in the station, including line protection, transformer protection, bus protection, capacitor protection, standby automatic switching, low frequency load shedding and other safety automatic devices. Various protections shall have the following functions: 1) fault recording.
Analysis of substation integrated automation system
2) storing a plurality of groups of fixed values
3) display and modify the fixed value locally
4) communicate with the monitoring system. Send fault information and action sequence according to the command of monitoring system. Current setpoint and self-diagnosis signal. A command is received from the monitoring system to select or modify a fixed value and check the clock. Communication should adopt standard protocols.
2. Data acquisition and processing functions
Include state data, analog data and pulse data.
1) state quantity collection
State quantities include: circuit breaker state, disconnector state, transformer tap signal, primary equipment alarm signal of substation, total accident trip signal, alarm signal, etc. At present, most of these signals are input into the system through photoelectric isolation, and can also be obtained through communication.
2) Analog acquisition
Typical analog quantities collected by traditional substations include bus voltage, line voltage, current and active and reactive power values. Feeder current, voltage and active and reactive power values.
3. Event recording, fault recording and ranging
Event records shall include protection action sequence records and switch trip records.
Substation fault recorder can be realized in two ways according to needs. One is to centrally configure a special fault recorder to communicate with the monitoring system. The other is decentralized, that is, the microcomputer protection device is used to record and calculate the distance, and then the digitized waveform and distance measurement results are sent to the monitoring system for storage and analysis.
4. Control and operation functions
The operator can remotely switch the circuit breaker, disconnector, transformer tap and capacitor bank through the screen of the background machine. In order to prevent the controlled equipment from operating when the system fails, manual direct tripping and closing means should be reserved in the system design.
5. Anti-misoperation locking function
6. Self-diagnosis function of the system
Each plug-in in the system should have self-diagnosis function and send data to the background computer and remote dispatching center. The real-time self-checking function of the equipment itself is convenient for maintenance and repair. By checking all parts of the equipment in real time by querying the standard input detection method, the internal faults and defects of the equipment can be quickly found, tips can be given and the fault location can be pointed out.
7. Data processing and recording
The formation and storage of historical data is the main content of data processing, including the data required by the dispatching center at the next higher level and the substation management and protection specialty, mainly including:
1) circuit breaker action times;
2) Cumulative truncation capacity and tripping operation times when the circuit breaker is disconnected;
3) Regularly record the active and reactive power of transmission line, active and reactive power of transformer, maximum, minimum and time of bus voltage;
4) Active and reactive power, daily peak and valley value and time of independent load;
5) Records of control operation and setting value modification.
According to the needs, this function can be realized locally in the substation, or in the telecontrol operation center or dispatching center.
8. Self-diagnosis function of man-machine contact system
Each plug-in in the system should have the function of self-diagnosis, and the information of self-diagnosis and fault is sent to the communication between the background machine and the remote dispatching center or between the operation control center and the remote control center regularly like the collected data.
9. Based on the "four telecontrol" of conventional telecontrol, this function adds the functions of remote modification of setting protection setting value, fault recording and remote transmission of ranging signals. Its information content is much larger than that of traditional telecontrol system. It should also have the functions of synchronization with the dispatching center, unified clock and local operation and maintenance.
Verb (abbreviation of verb) conclusion
From the above analysis, it can be seen that the comprehensive automation of substation greatly promotes the automation of power grid dispatching and the modernization of field operation management, and improves the safe and economic operation level of power grid. It will greatly improve the efficiency and reliability of the primary and secondary systems of the power grid, which is of great significance to ensure the safe and stable operation of the power grid. With the progress of technology and the improvement of software and hardware environment, its advantages will be further reflected. ■