Substation is an important part of power system and an important connection part of lines in power grid. Its function is to convert voltage, collect and distribute electric energy. Whether the substation can operate normally is related to the stability and safety of power system, so it is of great significance to monitor and protect the substation.
Substation computer monitoring technology is the combination of modern automation technology, electronic technology, communication technology, computer and network technology and power equipment, which organically combines the monitoring, control, measurement and work management of power supply departments in normal and accident situations. Complete the four remote functions of telemetry, remote communication, remote control and remote adjustment at the dispatching end. Improve the quality of power supply, strive for the safest, reliable, convenient, flexible and economical power supply, and make the management of power transformation and distribution more effective, so as to improve the quality of power supply, improve the service level and reduce the operating cost.
In recent years, substation computer monitoring technology has developed rapidly, but in order to better ensure the safety and reliability of computer monitoring system, it is necessary to improve the anti-electromagnetic interference ability of substation.
2. System composition
The computer monitoring system of substation consists of acquisition control modules with communication interfaces: multifunctional power integrated instrument, switch acquisition module, current acquisition module, analog acquisition module, relay control output module, field management machine, 24V DC power supply and central management machine. The central management machine is the centralized management center of this system. Generally installed in the general duty room where someone is on duty, it is used for real-time status display, parameter statistics, data analysis, history, fault alarm, control, report printing, etc. The whole distribution system.
3. System content
3. 1 Hardware part of substation computer monitoring system
For the main incoming line, outgoing line and bus connection of high-voltage centralized distribution station below 35kV, the functions of telemetry, remote communication and remote control can be realized by using power integrated instrument. The instrument is directly connected with CT and PT to collect high-precision AC signals. After discrete mathematical calculation, the electrical parameters of each loop can be measured (the measurement accuracy is 0.5%). The instrument has 8 switch inputs and 4 relay outputs, and has self-checking function, which can be used in conjunction with comprehensive relay protection devices.
(1) Connect ct and PT directly into the measuring loop of the power integrated instrument, and the electrical parameters of the loop can be measured. Realize the "telemetry" of the loop;
(2) The 8-way switch inputs of the instrument respectively collect the on-off state of the circuit breaker in the cabinet, the working position of the handcart, the energy storage state of the motor and the position of the grounding knife switch, collect and analyze the fault trip signal and internal fault in the comprehensive relay protection device, give an alarm and display the fault type of the circuit. Realize the "remote communication" of the loop;
(3) The relay outputs of the instrument are respectively connected to the opening and closing coils of the circuit breaker to realize the remote control of the circuit breaker, that is, the "remote control" of the circuit breaker.
In the 0.4kV low-voltage main incoming line and bus connection, the power integrated instrument is also used to realize the "three remote" function. The instrument is directly connected with CT and bus, collects high-precision AC signals, measures the actual power of the circuit, and realizes telemetry. At the same time, the remote communication of switching values such as opening and closing state, frame switch position, fault alarm and so on of the main incoming line and busbar switch circuit breaker is realized, and the remote control of the circuit breaker is realized.
3. 1. 1 remote communication
The switch value acquisition input module collects the switch state, switch fault alarm signal, pressure loss alarm signal, overvoltage alarm signal and frame switch position of each outlet circuit, and monitors the switch values such as the fan state, high temperature and ultra-high temperature signals of the transformer. A single module can usually collect 16 switch states.
3. 1.2 telemetry
(1) Each phase current of each outgoing loop is collected by the current input collection module, and a single module can collect 16 loop current. The current input module can collect the current of each loop, and calculate the actual power consumption of the loop according to the measured actual voltage and power factor.
(2) Collect analog signals such as temperature signal, humidity signal and liquid level signal of transformer through analog input module (each analog signal should have 4-20ma or 0-5v output).
3. 1.3 remote control
Through the relay control output module, the remote closing and opening functions of each low-voltage outlet circuit (switch with electric operating mechanism and voltage loss release) are realized.
In this system, the field management machine is located between the central management machine and each module, as the first-level bottom control unit, which increases the reliability of the system. Its function is: to carry out field debugging, adjust the parameters of each module by using the flexibility of field management, independently complete the field display work, send signals to the central management machine through the communication line (ILS485), and accept the commands sent by the central management machine at the same time. It can be used as a backup machine for the central management machine, with display function and self-checking function.
3.2 Software part of substation computer monitoring system
The monitoring software installed in the substation computer monitoring system is a special configuration software for power system based on Windows environment, which can run on MicrosoftWindowsNT, 2000 and XP platforms. It provides users with an all-Chinese interface, simple screen design, flexible configuration mode, high-performance DDE driver, supports a variety of industrial products, and follows the open database connection (ODBC) standard. Access to the database of this system is allowed through third parties (such as Microsoft Access and SQL Server).
Basic functional requirements of monitoring system:
Microcomputer monitoring system is the main way for users to master and control the running state of equipment. In particular, the improvement of the reliability of protection equipment simplifies the functions of man-machine interface and local control, so it should have safe and reliable performance, stable operation, perfect functions, friendly man-machine interface, simple interface, convenient reinstallation and operation maintenance, and it is best to have a monitoring system suitable for different communication modes that can be used uniformly by various equipment manufacturers.
3.2.2 Basic functions of monitoring system
(1) display function
Display the actual switchgear body diagram and primary system diagram of the substation, and display the on/off state of each switch on the primary system diagram;
Display three-phase current, three-phase voltage, active power, reactive power, active power, reactive power, frequency and power factor of each distribution line;
Display the on/off state and accident alarm category of each switch;
Display the real-time curve of electrical parameters of each loop;
Display transformer operation status, high temperature and ultra-high temperature alarm, gas protection;
Display the running status and faults of other process equipment.
(2) Alarm function
State alarm: When the switch of the power distribution system trips due to overload, short circuit fault or internal fault of the integrated relay protection device, the computer can give an audible alarm through the multimedia speaker, and automatically record the time, station number, loop name and accident category.
Over-limit alarm: when the power parameters of the power distribution system exceed the rated value or other process equipment exceeds the rated value, the computer can give an alarm through multimedia speakers and automatically record the time, station number and loop name.
Three-phase unbalance coefficient alarm: when the three-phase current or three-phase voltage of the power distribution system is unbalanced (the range can be customized), the computer will give an alarm through multimedia speakers and automatically record the time, station number and loop name.
(3) Control function
In the central management machine of the substation general duty room, the mouse can be used to control the closing and opening of various high and low voltage switches (with electric operating mechanism or AC contactor); At the same time, it can also realize the electric locking function and prevent the switch with locking circuit from misoperation;
In the central management machine, the mouse has the function of password identification when issuing operation orders, and only when the operator inputs the correct password can the operation orders be issued.
(4) Statistics and printing functions
Statistics and printing all monitored current values, voltage values, power values, frequency values and power factor values, as well as the 24-hour change curves of these parameters;
Statistics and print the running state change time, fault alarm time and category of each circuit breaker;
Statistics and print the operation time and operator code of each circuit breaker;
Statistics and print the electricity consumption and electricity consumption map of active and reactive power for 24 hours a day, and it also has the function of peak and valley charging.
(5) Historical records
The computer software of the duty room can permanently store the monitored and counted electrical parameters, state change time of each circuit breaker or switch, alarm fault category, operator code and time, and switching time, so as to analyze the operation of the whole power distribution system.
(6) Communication function
The system follows the KS485 communication protocol. The communication with the host follows RS485 or TCP/IP communication protocol.
(7) Self-check function
The system should have perfect self-diagnosis function. When the system fails, the diagnostic function will provide detailed fault information for timely troubleshooting.
4. System characteristics
4. The terminal data acquisition and control unit of1substation computer monitoring system is directly installed in the switch cabinet, and AC sampling is used to directly obtain AC 0-5A current signal or AC 0- 100V voltage signal (380/220 V low-voltage system directly obtains AC 0-220V or 0-380V voltage signal), so there is no need for various electric quantity transmitters, and there are various electric quantities on the switch cabinet.
4.2 Although the intelligent switch and intelligent switch cabinet have the monitoring function, centralized monitoring and remote scheduling can be realized as long as a communication cable is designed to lead to the central management machine in the duty room. However, because the communication protocols of various manufacturers are not uniform, it is difficult to realize networking, and the relay protection, signal and control circuits in the switchgear are still retained. Therefore, how to unify the communication protocol is the future development direction of the system, so that the system will be simpler.
4.3 The monitoring, recording and protection of high-order harmonics in substation computer monitoring system need to be improved.
4.4 With the application of new technology, the primary circuit breaker equipment is oil-free, and the secondary control elements are integrated and modularized without contact, which improves the reliability of equipment operation and reduces the workload of equipment maintenance.
4.5 Substation load adjustment, voltage adjustment, electricity reporting and other work are directly completed by dispatching, which changes the complicated links of dispatching orders and substation operators receiving orders to perform operations in the past, and reduces the occurrence of misoperation accidents in substation operation.
4.6 Dispatching can directly monitor the operation of substation equipment, and provide original data timely and accurately in case of failure, which provides convenience for accident handling.