Substation is an indispensable and important part of power system. It undertakes the heavy task of power conversion and power redistribution and plays an important role in the safety and economic operation of power grid. In order to improve the safety and stability of substation operation, reduce operating and maintenance costs, improve economic efficiency, to provide users with high-quality electrical services, integrated substation automation technology began to rise and is widely used.
Substation automation is the secondary substation equipment (including control, signal, measurement, protection, automatic devices and remote devices, etc.) application of computer technology and modern communication technology, through functional combination and optimization of the design of the substation to implement automatic monitoring, measurement , Control and coordination, and scheduling and communications and other integrated automation system. The realization of integrated substation automation can improve the safety and economic operation of the power grid, reduce capital investment and provide a means for promoting unmanned substations. The rapid development of computer technology, information technology and network technology has led to the progress of substation automation technologies. In recent years, with the development of digital electrical measurement systems such as photoelectric transformers or electronic transformers, smart electrical equipment and related communication technologies, integrated substation automation systems are moving in the direction of digitization.
First, the main function of integrated substation automation system
The basic functions of substation integrated automation system are reflected in the functions of the following six subsystems:
1 monitoring subsystem
2 relay protection subsystem;
3 voltage and reactive power integrated control subsystem;
4 low-frequency power system load control subsystem;
5 standby power from the vote control subsystem;
6 communication subsystem.
This part of the content is rich, and there are many documents described in detail, so this article will not elaborate.
Second, the traditional substation automation system
System structure
At present, the structure of substation integrated automation system both at home and abroad has the following three categories from the design idea classification:
(1) centralized
Using different grades of computers, expanding its peripheral interface circuits, centralized collection of substations analog, digital and other information and switch to focus on processing operations, respectively, to complete computer monitoring, computer protection and some automatic control functions. Its characteristics are: high performance requirements of the computer, scalability, poor maintainability, suitable for medium and small substations.
(2) distributed
Substation by the monitored object or system functions, multiple CPUs work in parallel, the CPU between the use of network technology or serial data communication. Distributed system expansion and maintenance of convenience, local failure does not affect the normal operation of other modules. This mode can be installed on the group screen or group screen.
(3) decentralized distributed
Each data acquisition interval unit, control unit (I / O unit) and protection unit scattered in situ installed on the switchgear or other equipment in the vicinity of each unit independent of each other only through the communication network interconnection, and with the substation level control master unit Communication. Functions that can be done in the bay do not depend on communication networks such as protection. Communication network is usually fiber optic or twisted pair, to maximize the compression of secondary equipment and secondary cables, saving construction investment. Installation can be dispersed installed in the interval, but also in the control room to focus on the group screen or group screen, but also part of the control room, the other part of the spread in the switch cabinet.
2. Existing problems
The substation integrated automation system has obtained a good application effect. However, there are also some shortcomings. The main manifestations are as follows: 1 The first and second information exchange or continuation of the traditional cable connection mode, high cost, inconvenient construction and maintenance; The second part of the data acquisition a large number of repetitions, a waste of resources; 3 information standardization is not enough, low degree of information sharing, multiple systems coexist, equipment, equipment and systems interoperability difficulties, the formation of information islands, the information is difficult to be comprehensive application; 4 When an accident occurs, there will be a large number of incident alarm information, the lack of an effective filtering mechanism, interfere with duty operators on the right to judge the fault.
Third, digital substation
Digital substation is the next phase of substation automation development, "State Grid Corporation" Eleventh Five-Year "Science and Technology Development Plan" has made it clear that in the "Eleventh Five-Year" period to study the digital substation and the construction of a demonstration station, and has been completed digital substation And put into operation, such as Fuzhou Convention and Exhibition change 110 kV digital substation.
1. Digital substation concept
Digital substation refers to the complete digitization of information collection, transmission, processing and output substation, the basic characteristics of intelligent equipment, communication network, operation management automation.
Digital substation has the following main features:
(1) a device intelligence
Electronic transformers with digital outputs, smart primary devices such as smart switches (or traditional switches with smart terminals). A device and secondary equipment between the optical transmission of digital coded information exchange sampling value, status, control commands and other information.
(2) secondary equipment network
Secondary equipment used to exchange communication network analog, switch and control commands and other information, cancel the control cable.
(3) operation management system automation
Should include automatic fault analysis system, equipment health monitoring system and program control system and other automation systems to enhance the level of automation and reduce the operation and maintenance of the difficulty and workload.
2. The main technical characteristics of digital substation
(1) Data Acquisition Digitization
The main symbol of digital substation is the use of digital electrical measurement system (such as photoelectric transformer or electronic transformer) acquisition of electricity
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