Summary:In order to solve the problems of the current environmental monitoring system in the high-voltage switch distribution room in terms of reliability, scalability, flexibility and methodology, a new design scheme of environmental monitoring system was proposed. The system is composed of Siemens programmable controller (PLC) and sensors, etc., which can monitor SF6 gas concentration, oxygen content, ambient temperature and humidity and other parameters in real time in the environment of high-voltage switching power distribution treasure. This system has the characteristics of high reliability, convenient expansion, stable performance, convenient maintenance, strong anti-drying ability, etc., which can effectively ensure the personal safety of the staff entering the high-voltage switch distribution room.
Keywords:High Voltage Switch Distribution Room: SF6: Environmental Monitoring System.
0.Introduction. High-voltage switch is an important part of the smart grid, and the safe and reliable operation of high-voltage switch is an important guarantee for the safe operation of the entire power grid. At present, high-voltage switches all use SF6 gas as insulating protective gas, SF6 is a colorless and odorless gas at room temperature, and the pure SF6 body itself is non-toxic, but the decomposition products after high pressure and arc action contain a variety of toxic gases, once the toxic gas leaks into the high-voltage switch room environment, it will bring serious harm to the health of the staff in the high-voltage switch room, therefore, real-time monitoring of whether there is SF6 gas leakage in the high-voltage switch room environment. At the same time, China's electrical safety operation regulations also clearly stated that an environmental monitoring system should be installed in the high-voltage switch distribution room, and the system is required to have the function of automatically starting the exhaust fan for exhaust when the SF6 gas concentration exceeds the standard.
1.Problems with environmental monitoring systems.
1.Selection of 1SF6 gas concentration sensor.
SF6 gas concentration sensor is an important part of the whole environmental monitoring system, the quality of the sensor, whether it works reliably directly determines the accuracy of SF6 gas concentration detection in the environment, and then determines the accuracy of the system to control the field exhaust fan.
At present, the SF6 gas concentration sensor on the market mainly adopts the following principles: semiconductor principle, laser principle, electrochemical principle, infrared absorption principle. The SF6 gas concentration sensor based on the principle of semiconductors can not be quantitatively measured, but can only be detected qualitatively, and there will often be leakage alarms and false alarms: the quantitative detection accuracy of the SF6 concentration sensor based on the laser principle is not high, the structure is complex, the laser tube is fragile, and the maintenance is difficult: the SF6 concentration sensor based on the electrochemical principle has high quantitative detection accuracy, but the diaphragm and electrolyte of the sensor need to be replaced frequently, which is not easy to maintain.
1.2. The output form of the detection signal.
In the output form of the sensor signal, there are mainly two output forms: 4 20mA analog output form and RS485 bus output.
4 20mA analog output form, need to connect the signal line of each detection channel to the monitoring host, wiring cumbersome, difficult to expand.
Some manufacturers use RS485 bus communication mode to form an environmental monitoring system, but due to the communication protocol is too simple, the anti-interference ability is not strong, the system is often interfered by strong magnetic field and strong electric field, and the communication is not smooth, and the detection data cannot be transmitted.
1.Selection of 3-channel switching mode.
Some manufacturers use the channel time-sharing switching method to realize the signal detection of multiple monitoring points, which is not real-time, and the detection accuracy is low.
2.System composition.
The system is composed of SF6 concentration oxygen content composite sensor, SIEMENS programmable controller (PLC), Kunlun Tongtai touch screen, temperature and humidity sensor, infrared sensor, sound and light alarm, control relay, etc. Its composition is shown in Figure 1. The system adopts Siemens SIMATICS7-200 series programmable controller (PLC) as the core component of data acquisition and control, Kunlun Tongtai touch screen as the data display and storage component, and adopts the SF6 gas concentration sensor imported from Germany with infrared absorption principle and the oxygen content sensor imported from Japan as the main components, with communication, power isolation, signal isolation, anti-electromagnetic interference and other circuits to form the SF6 concentration oxygen content composite sensor, so that the sensor has high detection accuracy, With the advantages of good stability, strong anti-interference ability and convenient maintenance, the RS485 bus output is used to make the system expansion easier and fully meet the requirements of the site.
3.System features.
3.1. Data detection and control.
When the concentration of SF6 gas at a monitoring point in the distribution room environment is higher than the set alarm value, or the oxygen content is lower than the set value, the programmable controller starts the on-site exhaust fan through the control relay for exhaust ventilation, and at the same time starts the sound and light alarm to output the sound and light alarm; When the concentration or oxygen content of SF6 gas in the environment reaches the standard, turn off the on-site exhaust fan and stop the sound and light alarm; When there are personnel entering the power distribution room, the system automatically starts the on-site exhaust fan for exhaust, and in addition, the programmable controller can also start the on-site exhaust fan regularly or manually start the on-site exhaust fan according to the setting.
3.2. Dynamic parameters of monitoring points are equipped with gastric tables.
Due to the different environmental monitoring points of different high-voltage switch distribution rooms, different sensor addresses, and different configuration methods and control methods of exhaust fans, the system is specially set up with a dynamic parameter configuration table, so as to achieve a high degree of flexibility and scalability of the system. The specific functions are described as follows:
1) Flexible configuration of monitoring point installation.
As shown in Figure 2, the first column of the dynamic parameter configuration table is the number of monitoring points, and only 8 monitoring points are displayed in the figure, which can be 16 channels, 32 channels, 64 channels, etc. in practical applications. When a monitoring point is equipped with an SF6 concentration oxygen content composite sensor, press the button behind the corresponding monitoring point, and the symbol on the button changes from "X" to " indicates that the monitoring point is installed with an SF6 concentration oxygen content composite sensor, on the contrary, when the symbol "X" on the button behind the monitoring point indicates that there is no sensor installed at this monitoring point, and through the operation button, you can switch between "X" and "". The installation of the SF6 concentration transmitter and the oxygen content transmitter can be set separately, and the installation of the SF6 concentration oxygen content composite sensor requires both SF6 and 02 to be set to " " The setting method of the temperature and humidity transmitter is the same as that of the SF6 02 transmitter.
2) Flexible configuration of transmitter address.
The transmitter adopts the digital output method of RS485 bus, and each transmitter is set with a fixed address identification before leaving the factory. In this system, by entering the address in the corresponding transmitter address setting box of the corresponding monitoring point, the communication address of any transmitter installed in the system can be conveniently set, so that after the transmitter is replaced and increased in the system, the system program does not need to be modified, and the flexibility and practicability of the system are greatly enhanced.
3) Flexible configuration of exhaust fan unit control.
When the concentration of SF6 gas in the distribution room environment exceeds the standard or the oxygen content is too low, the system has the function of automatically starting the on-site exhaust fan for exhaust. The system divides the on-site exhaust fan into 4 groups to control them separately, and through the setting of the start of the 4 groups of exhaust fans after the parameters of each monitoring point exceed the standard, the starting scheme of the exhaust fan can be flexibly set, and when there are multiple monitoring points in the environment that exceed the standard, the starting scheme of the exhaust fan will be combined and implemented.
4) System parameter configuration table.
In order to enhance the flexibility of the system and adapt to the requirements of different sites, the system has set up a system parameter configuration table.
4.Accuray distribution room environmental monitoring system.
4.1 Overview.
The integrated monitoring system of the power distribution room includes an intelligent monitoring system screen, a communication management machine, a UPS power supply, a monitoring subsystem (PTZ ball machine, a gun machine), an environmental monitoring subsystem (temperature, humidity, flooding, smoke detector), a control subsystem (lighting, air conditioning, dehumidifier, fan, water pump), an access control monitoring subsystem (card reader, door opening button, magnetic lock), and a security monitoring subsystem (double detector).
4.2. Application place.
It is suitable for the engineering design, construction, operation and maintenance of power supply and distribution automation system of 35kV and below users such as rail transit, industry, construction, schools, commercial complexes, etc.
4.3. System structure.
4.4. System functions.
4.4.1. Real-time monitoring.
It can display the operation status of the equipment in the distribution room, monitor the environmental parameter information of the distribution room in real time, and display information about faults and alarms in real time.
4.4.2. Data query.
In the human-machine interface, the operating data of individual devices in the distribution room can be directly viewed.
4.4.3. Curve query.
You can directly view the curves of each electrical parameter.
4.4.4. Run the report.
Query the operation data report of the equipment in the power distribution room.
4.4.5. Real-time alarms.
With real-time alarm function, the system can send alarms for events such as temperature, humidity, harmful gases, equipment failures or communication failures in the distribution room.
4.4.6. Historical event inquiry.
It can store and manage all event records generated, which is convenient for users to trace system events and carry out historical traceability, query statistics, and accident analysis.
4.4.7. User rights management.
The user rights management function is set up to define the login name, password, and operation permissions of different levels of users.
4.4.8. Network topology diagram.
It supports real-time monitoring and diagnosis of the communication status of each device, and can completely display the entire system network structure.
4.4.9 remote control function.
Remote control of equipment throughout the power distribution system can be carried out.
4.5. System hardware configuration.
5.Conclusion.
The monitoring system designed in this paper is of great significance for the safe production of power systems, substations and other power systems, and for ensuring the health of workers. With the vigorous promotion of smart grid work by the state, the SF6 environmental monitoring system of high-voltage switch distribution room will inevitably play an increasingly important role in practical application.