How to Realize the Function of Substation Automation? Introduction to Substation Automation

Substation automation is a new technological transformation. The use of this technology has made the realization of the automation system much simpler, and its performance is also much better than the previous system.

1. Development of substation automation

Substation automation has been one of the hot spots in my country's power industry since the 1990s. The reason why it has become a hot spot is due to the needs of construction and market factors. There are about 18,000 35-110kV substations put into power grid operation nationwide (excluding user transformers), about 1,000 220kV substations, and about 50 500kV substations. Moreover, the number of substations increases at a rate of 3 to 5 every year, which means that thousands of new power stations are put into operation on the grid every year. At the same time, according to the requirements of the power grid, many substations undergo technical transformation every year to improve the automation level. In the past ten years, my country's substation automation technology, whether it is imported from abroad or domestically developed systems and equipment, has developed significantly in technology and quantity.

2. System structure of substation automation

From the point of view of the design idea of the substation automation system, the designer's view on the measurement and control of the substation has been transformed from part to whole. In the substation automation system, object-oriented technology has become a very popular trend, that is, it does not simply consider a certain quantity, but equips a certain equipment with complete protection and monitoring function devices to complete specific functions, thus ensuring the safety of the system. Distributed openness. From the trend of technological development, the future measurement and control equipment will be fully integrated with primary equipment, that is, to realize the so-called intelligent primary equipment. Each object contains a series of functions and information bases such as protection, monitoring, billing, operation, and locking. For automation, it is only a pair of communication twisted pair, which is connected to the computer in the form of a network.

The development of design ideas has led to the development of system structure. The original automation system basically can only configure screens in a centralized manner. Due to the deepening of object-oriented design ideas and the overall design of primary equipment, the system structure will change from centralized to partially distributed or fully distributed. With the development, the substation may no longer have a large-scale measurement and control panel and a large number of copper cables connecting the signal source and the measurement and control panel. The computer monitor is even just a portable machine for temporary monitoring and operation.

The completely distributed implementation relies on the fast-growing computer and network technology, especially the field bus technology. The use of this technology has made the implementation of the automation system much simpler, and its performance is much better than the previous system, and it can solve the real-time problem of RS-485 link information transmission and the capacity problem of signal transmission in the previous system.

3. Substation integrated automation system

The substation integrated automation system refers to the combination of some interrelated units that achieve a given goal by performing specified functions. The functions of secondary equipment are recombined and optimized, and the operation status of all equipment in the substation is monitored and measured.

4. The development direction of substation integrated automation system

4.1 Change of system structure
The structure of substation integrated automation system will gradually develop from centralized control and function dispersion to decentralized network. The traditional system structure is considered in terms of function dispersion, and the development trend will develop from one functional module managing multiple electrical units or compartment units to one module managing one electrical unit or compartment unit, and the geographical location is highly dispersed. In this way, the possible impact on the power grid when the automation system fails is greatly reduced, and the independence and adaptability of the automation equipment are stronger.

4.1.1 Development of Intelligent Electronic Devices (IEDs)
4.1.2 Application of photoelectric transformer

4.2 Development of monitoring system
The development of the monitoring system is mainly manifested in two aspects, that is, the gradual application of the substation remote viewing system and the continuous improvement of artificial intelligence in the application of fault diagnosis.

4.2.1 Application of remote viewing system
4.2.2 Development and application of artificial intelligence technology

5. Development of communication methods for substation automation

5.1 Development and application of industrial Ethernet
Compared with field bus, industrial Ethernet is a unified bus network technology, which has general advantages, and has the advantages of low price, fast speed, and easy networking. There are two models of industrial Ethernet: one is a hybrid model (Ethernet is connected to other buses); the other is the so-called "transparent factory" type, that is, a unified industrial Ethernet communication protocol is adopted from the upper layer to the lower layer. The hybrid industrial Ethernet technology is very mature, and the "transparent factory" industrial Ethernet is a research hotspot in the field of industrial control. Various solutions have been proposed at home and abroad, and many scholars are studying each solution. In the process of continuous development and improvement, it is believed that in the future, industrial Ethernet will bring new vitality to the substation automation system.

5.2 Development and application of Bluetooth technology
Bluetooth technology is an open global specification for wireless data and voice communication. It is a short-range radio technology based on low-cost short-range wireless connection and establishes a special connection for fixed and mobile device communication environments. It solves the problem of Ethernet It is used for the difficult problem of substation automation wiring. The technology has the characteristics of low power, miniaturization, low cost and adapting to the network age. Bluetooth technology is a developing technology, and its application is in its infancy, but the advantages of unified Bluetooth technology standards and intellectual property sharing are very obvious, and its future development is limitless. It can be foreseen that the wireless communication between many devices in the substation will be realized in the near future.

6. Function realization of substation automation

6.1 Microcomputer protection: It is to protect all electrical equipment in the station, including line protection, transformer protection, busbar protection, capacitor protection and automatic switching, low-frequency load shedding and other safety automatic devices.

6.2 Data acquisition: including status data (circuit breaker status, isolating switch status, transformer tap signal and substation primary equipment alarm signal, etc.), analog data (bus voltage, line voltage, current, power value, frequency, phase, etc. and transformer oil temperature, substation room temperature and other non-electric power), and pulse data (output pulse of pulse watt-hour meter, etc.).

6.3 Event records and fault recording and ranging: event records should include protection action sequence records and switch trip records.

6.4 Control and operation lockout: Operators can remotely operate circuit breakers, isolating switches, transformer taps, and capacitor bank switching through the background screen. Operational locking includes: computer five-defense and locking system, circuit breaker, knife switch operating locking, etc.

6.5 Synchronization detection and synchronous closing.

6.6 Local control of voltage and reactive power: Generally, it is realized by adjusting transformer taps, switching capacitor banks, reactor banks, etc. Data processing and recording: formation and storage of historical data.

6.7 Human-machine contact.

6.8 Self-diagnostic function of the system: each plug-in in the system should have a self-diagnostic function, and the self-diagnostic information, like the collected data, is periodically sent to the background machine and the remote dispatch center or operation control center.

6.9 Communication with the remote control center: telecontrol "four remotes" and remote modification of setting and protection settings, fault recording and remote transmission of ranging signals, etc. The system should have the backup and switching functions of the communication channel to ensure the reliability of the communication. At the same time, it should have different communication interfaces with multiple dispatch centers, and the MODME of each communication port should be independent of each other. The protection and fault recording information can be connected to the dispatching center through independent communication, and the communication protocol should meet the requirements of the dispatching center and meet the national and industrial CE standards.

6.10 Fire prevention and security system.

7. Structural model of substation automation

From the perspective of the development of domestic and foreign substation comprehensive automation, there are roughly the following structures:

7.1 Distributed system structure
Multiple computer single-function devices distributed according to the monitored objects or system functions of the substation are connected to a network that can share resources to realize distributed processing. The "distribution" mentioned here is based on the physical distribution of substation resources (the geographical distribution is not emphasized), and the emphasis is on the study of distribution issues from the perspective of computers. This is an ideal structure. To achieve a fully distributed structure, it has strong advantages in scalability, versatility and openness. However, in actual engineering applications and technical realizations, many A series of problems that are difficult to solve, such as the harsh operating environment, anti-electromagnetic interference, information transmission channels and reliability assurance problems in the decentralized installation arrangement, etc., the technology is not very mature enough, blindly pursuing a completely distributed structure, Ignoring engineering practicality is unnecessary.

7.2 Centralized system structure
The hardware devices and data processing of the system are centrally configured, adopting a centralized control structure composed of a front-end machine and a back-end machine. The front-end machine completes functions such as data input and output, protection, control and monitoring, and the back-end machine completes data processing and display. , printing and remote communication functions. At present, many domestic manufacturers still belong to this structure. This structure has the following disadvantages: the front-end management machine has heavy tasks and many leads, which is an information 'bottleneck', which reduces the reliability of the entire system, that is, when the front-end machine fails In this case, all local and remote information and functions will be lost. In addition, it still cannot save money from the perspective of engineering design. Cables still need to be laid, and it is difficult to expand some functions required by automation. It is worth mentioning here that the reason for the formation of this structure is that the early development process of substation secondary products was classified and independently developed according to the protection, measurement, control and communication parts, and was not carried out under the guiding ideology of the entire system design. With the advancement of power system automation and the requirements of power system automation, when designing substation automation projects, most of them adopt the method of "patchwork" according to functions, which leads to the decline of system performance indicators and many unsolvable engineering problems.

7.3 Hierarchical distributed structure
According to the control level and objects of substations, a two-layer distributed control system structure is set up for the control level of the whole station (station level) and the control level of local units (segment level).

The station-level system generally includes the station control system (SCS), station monitoring system (SMS), station engineer workbench (EWS) and communication system (RTU) with the dispatching center:

Station Control System (SCS): It should have rapid information response capability and corresponding information processing and analysis functions, and complete operation management and control in the station (including local and remote control management), such as event recording, switch control and SCADA data collection function.

Station monitoring system (SMS): It should monitor all operating equipment in the station, and provide operating status and abnormal information for the station control system, that is, provide comprehensive operating information functions, such as disturbance records, operating status of equipment in the station, and secondary equipment input/exit status and equipment ratings, etc.

Station engineer workbench (EWS): It can perform functions such as status inspection, parameter setting, debugging and inspection of equipment in the station, and can also use a portable computer for on-site and remote maintenance.

The above is basically divided into blocks according to the general functions. The hardware can be implemented in one station control computer according to the functions and information characteristics, or two double standbys, or can be arranged separately according to functions, but it should be able to share data information and have multi-tasking time. Real processing functions.

At the segment level, the object-oriented distributed configuration of primary equipment (transformers or lines, etc.) in the station is used in the horizontal direction. In terms of function distribution, the principle of decentralization is adopted, that is, all functions that can be completed locally at this interval will never depend on the communication network. Function exceptions, such as the realization of functions such as distributed wave recording and small current grounding line selection.