Summary:The substation automation control system is a comprehensive system for automatic monitoring, measurement, control and coordination of the substation. This paper analyzes the computer monitoring system and monitoring protection in the automatic control of substation, and focuses on several problems in the application of automatic control system of substation: communication network and standby power self-throwing device.
Keywords:monitoring systems; Microcomputer relay protection; Communication networks.
0 Introduction. With the continuous increase in the construction of infrastructure in recent years, the scale of investment and construction of power grid has also been expanding, and higher requirements have been put forward for the safe, stable and intelligent operation of the power grid, especially with the rapid development of power electronics technology in the world today, the degree of automation of substations has become higher and higher. In this context, a system of automatic control and unmanned operation has been developed - substation integrated automation system. Using computer control technology, network communication and other technologies, the automatic control system of the substation integrates the primary and secondary equipment (including data acquisition, operation control, protection, ATS automatic conversion equipment, etc.) of the substation with functional blocks, groups and optimizes the functional blocks, so as to realize the timely measurement, monitoring, control and recording of the substation equipment.
1. The basic functions of the substation monitoring system.
1.1 Collect and process data.
The operating temperature, bus voltage, current, power factor and other parameters of the main transformer are collected and processed in real time by the data acquisition unit. The microcomputer system updates the database by collecting the above data.
1.2 Control Functions.
The control function includes local and remote control of circuit breakers, arc suppression coils, main transformer fans, and control reactive power compensation contactors of various voltage levels of the substation.
1.3. Alarm event handling.
There are two types of alarms in the control system, one is prompt alarm and the other is accident alarm. The former includes general abnormal alarms of equipment status, data overruns, abnormal status of a unit and module of the master station and slave, etc., while the latter includes circuit breaker tripping caused by non-operation, protection interlock switch action, etc.
1.4 Chronological event recording function.
The computer monitoring system collects and records the action signal information of the circuit breaker status, main transformer parameters, primary and secondary line parameters, and protection components in millis-level time units, and can display them on the display and print them on the printer.
1.5 **Statistical calculations.
According to the real-time data of sampling, the voltage value, current value, active power, reactive power, active coefficient, main transformer temperature value, quantity action state, etc. of each time interval can be calculated, and the time-based statistical data of the above data divided by year, month and day can be given. For example, the value of voltage and current, the pass rate of power factor, etc.
1.6 Display and Print Screen.
The primary wiring diagram and DC system diagram of the substation distribution system can be displayed on the display, which can display statistical data, some key data historical change curves, some alarm events, and can print historical data, alarm records, etc.
1.7 Systematic self-diagnosis and self-diagnosis.
The monitoring system can diagnose the hardware and software operation of the system in real time, and once an abnormality is found, it can generate and send out alarm information. The scope of self-diagnosis includes: master station, slave system, IO unit, module, peripherals, software failure, etc., non-serious prompt alarm, the system can carry out self-alarm.
1.8 Weekday management features.
The weekday management function refers to the daily inspection, management, maintenance, update and optimization of the system carried out by the engineer responsible for the computer monitoring system. It includes two aspects: function maintenance management and database maintenance management. Functional maintenance management includes the start and stop control of the automatic control system, the monitoring of the running status of various application functions, and the loading, generation and editing of various application data display charts. Database maintenance is the addition, deletion and modification of application parameters in the database by engineers.
2. Relay protection functions and applications.
2.1 Protection Function.
1) The transformer is generally equipped with two main protections: differential protection and gas protection, and backup protection such as zero sequence current protection and overcurrent protection.
2) The TT&C protection of lines below 110kV is equipped with reclosing and overcurrent protection, and the TT&C protection of lines above 110kV is equipped with zero-sequence current protection and comprehensive reclosing protection.
2.2. The principle of microcomputer relay protection.
1) Hardware system: The microcomputer relay protection hardware system is composed of a large number of ICs (integrated circuits), usually composed of CPU, timer, memory, register, AD converter, D conversion and other components. The information acquisition work in the microcomputer relay protection system is completed by relying on the data acquisition system (which is mainly composed of sampling and holding circuits, analog-to-digital converters (AD converters), etc.
2) software system: the software system is mainly divided into monitoring program and system program, the function of monitoring program is to include input, output status, setting, modification and display of the parameter value of the protection device to monitor, while controlling the hardware circuit state of the microcomputer protection device; A system program is a system program that monitors the operating environment of the program. The main functions of the system program are: 1) cyclic self-test function, 2) interrupt response function, 3) event processing function.
3. Analysis and study of the main issues.
3.1 Communication technology.
The following communication network technologies are common in the substation automatic control system: (1) the traditional RS-232 485 fieldbus is used for low-speed data transmission, (2) the local control network such as the common Lonworks and CAN communication technologies are used to realize the medium-speed transmission of data, and (3) the ethernet is used to realize the distributed connection of the equipment in the station. The system structure is composed of a monitoring host, a switch, and an on-site control module, and the monitoring host transmits real-time data through Ethernet to realize man-machine dialogue and complete monitoring and management functions.
3.2 ATS (Automatic Standby Power Switching).
In order to ensure that the ATS can work properly, the following points need to be noted:
1) ATS should be able to monitor the voltage status of the working bus in real time, when the working bus failure, power transformer failure, circuit breaker tripping for some reason, will cause the loss of voltage of the working bus, then the ATS should be able to automatically switch to put into use in an instant, in order to ensure the uninterrupted power supply of the load.
2) When the ATS loses power, the ATS self-throwing device should not operate, because if it barely responds to the accident in this state, the ATS will not be able to play any role if it cuts into the network. (3) When the power supply system fails, the system fault must be eliminated first, and then the ATS can be put into use, otherwise it is very likely that the backup power supply will be put into the fault network, so that the faulty network can not only not be relieved of the fault, but the degree of failure will further deteriorate the consequences.
4 Acrel-1000 substation integrated automation system.
4.1. Overview of the program.
The ACREL-1000 substation integrated automation monitoring system is composed of two layers of equipment at the station control layer and the interval layer in terms of logical function, and is connected by a hierarchical and open network system. The station control layer equipment includes a monitoring host, provides a man-machine contact interface for station operation, realizes functions such as management and control interval layer equipment, forms a whole station monitoring, and communicates with remote monitoring and scheduling; The interval layer is composed of several secondary subsystems, and the local monitoring function of the interval layer equipment can still be completed independently in the case of the failure of the station control layer and the station control layer network.
According to the specific situation of the project, the design scheme has high reliability, easy to expand and friendly man-machine interface, the performance ratio is superior, the monitoring system is composed of two parts, the station control layer and the interval layer, the use of hierarchical distributed network structure, the station control layer network using TCP IP protocol Ethernet. The station control layer network adopts a single-network and dual-machine hot standby configuration.
4.2. Application place:
It is suitable for the operation monitoring and control management of the user-side distribution and power system with a voltage level below 35kV in various industries such as public buildings, industrial buildings, and residential buildings.
4.3. System structure.
4.4. System function ACREL-1000 substation integrated automation system, intuitively display the operation status of the distribution line in the form of a distribution diagram, real-time monitoring of the voltage, current, power, power factor and other electrical parameter information of each circuit, and dynamically monitor the closing and opening status of the circuit breaker, isolation switch, ground knife and other closing and opening status of each distribution circuit and related faults, alarms and other signals.
The monitoring system has an accident alarm function. The accident alarm includes the circuit breaker tripping and the action signal of the protection device caused by abnormal operation; Warning alarms include general equipment displacement, abnormal status information, analog or temperature overruns, etc.
1) Accident alarm. When the accident status mode, the accident alarm immediately sends out an audio alarm (the alarm volume is adjusted arbitrarily), the display screen of the operator workstation changes and flashes to indicate the disposition of the equipment, and the pop-up window displays the red alarm clause, the alarm is divided into real-time alarm and historical alarm, and the historical alarm clause has the function of selecting query and printing.
Accident alarms are manually acknowledged once at a time. Once the alarm is confirmed, the sound and flash will stop.
In the stage of the second accident alarm, the next alarm signal is allowed to enter, that is, the second alarm does not cover the content of the previous alarm. Alarm processing has the ability to define or exit on the host computer.
2) For each measured value (including the calculated value), the user sequence sets four specified operating limits (physical lower limit, alarm lower limit, alarm upper limit, physical upper limit), which are defined as warning alarms and accident alarms respectively.
3) The number of times the switch accident is tripped to or the number of times the switch is pulled to, and the alarm message is launched to prompt the user to overhaul.
4) Newspaper type.
The report has a variety of manifestations, including pop-ups, screen flashing, sound and light alarms, voice, text messages, etc., but not limited to the above methods, users can add or modify alarm information according to their own needs.
The operator controls the electrical equipment that needs to be controlled. The monitoring system has an operation monitoring function, which allows the guardian to implement monitoring on the operator's workstation to avoid misoperation.
There are four levels of operational control:
The first control, equipment on-site maintenance control. Control with priority. When the operator places the remote local toggle switch of the local equipment in the local position, all other control functions are locked and only the field operation is performed.
Level control, spacer layer backup control. Its switching with the ** control is done at the spacer level.
The first control, station control layer control. This level of control is done on the operator's workstation with a remote control level switching.
The fourth level of control, remote control, priority.
In principle, spacer control and equipment on-site control are used as backup operation or maintenance operation means. In order to prevent misoperation, step-by-step operation is required in any control mode, that is, selection, return, execution, and set up operator and guardian passwords and lines** at the station level to ensure the operation and correctness. For any operation mode, ensure that the next operation will not be carried out until the previous operation step is completed. Only one control method is allowed at a time.
The equipment included in the control includes: circuit breaker of 35kV and below; 35kV and below disconnecting switch and grounding switch with electric mechanism; station electricity 380V circuit breaker; main transformer taps; Remote resetter and remote return connector of relay protection device.
3) Timing control. The operator performs timing control operations on the electrical equipment that needs to be controlled, sets the start and shutdown time, and completes the timing control.
4) Monitor the control output of the system. The contact of the control output is a passive contact, and the capacity of the contact is 110V (220VA) for DC, 220V and 5A for AC.
The system is set up with the user rights management function, which can prevent unauthorized operating systems from defining permission groups (such as administrators, maintainers, watchman groups, etc.) with different operation permissions, and add user names and passwords to each permission group to provide reliable guarantee for system operation, maintenance and management.
5 System hardware configuration.
6 Conclusion. In today's world, with the rapid improvement of science and technology and social productivity, the use of substation automation control system can reduce personnel input, improve work efficiency, ensure the high-quality, stable, continuous and reliable operation of electric power, and improve the automatic control level of the entire power system. With the rapid development of modern power electronics technology, network communication technology, automation control technology, computer technology, AI and other technologies, the automation degree of the substation automation control system will be further improved, and its function will be more perfect and powerful, so as to continuously meet the needs of the rapid progress of society for the development of electric power.