GIS is gas insulated fully enclosed combined electrical apparatus is a high, fine and sharp transmission and substation equipment developed in recent decades, and the maintenance workload is small, high reliability of operation, in power plants, substations, etc. are widely used.
In GIS equipment, SF6 gas is generally used as insulation and interrupting medium. SF6 gas is a non-toxic, tasteless, colorless, odorless, non-combustible synthetic gas with high electrical strength and excellent interrupting performance, which plays a decisive role in the performance of GIS equipment.
The existing GIS equipment commonly uses density relays to monitor SF6 pressure in the equipment in situ, and relies on the pressure node on the SF6 relay to send SF6 pressure low alarm and pressure low blocking signal to the remote location.
As there is no online monitoring system, SF6 gas leakage and its development trend cannot be found in time, which is easy to occur due to serious SF6 leakage, endangering the safety of the main equipment, causing damage to the main equipment and affecting the stable operation of the system.
In recent years, with the rapid progress of sensor technology, microelectronics technology and computer technology, various GIS equipment online monitoring systems have emerged, especially SF6 density of gas online monitoring system has been gradually applied to many large power projects in the international power grid.
In the hydropower station project, SF6 gas density online monitoring system collects SF6 gas status parameters in each gas chamber of GIS.
So as to achieve real-time and remote monitoring of SF6 gas density in the production process as well as historical data analysis, strengthen the monitoring means and better ensure the safe and stable operation of equipment.
The whole GIS gas density online monitoring system is mainly composed of SF6 gas density relay, relay and conversion module, and field service computer.
The system firstly collects pressure and temperature in high voltage electrical equipment through pressure and temperature sensors in SF6 relay, converts them into standard signals of 4~20mA DC and outputs them to the lower computer.
Then the lower computer uses its internal C51 microcontroller to calculate and process the collected 4-20mA DC standard signals to obtain the density value, and finally uploads it to the upper computer (field service computer) in the monitoring room of the substation through RS485 bus.
The upper computer uses industrial control configuration software to control the central system, receiving and displaying the temperature, pressure and density values from the lower computer.
Finally, the upper computer controls the central system for data processing and display, and can set the alarm value and blocking value, issue alarm prompt when there is gas leakage, and realize the storage and query of historical data and trend curve.
SF6 pressure monitoring is an indispensable means of monitoring the operation of GIS equipment, with the widespread use of GIS equipment in the power system, GIS SF6 gas density online monitoring system will also continue to be promoted and applied.
With GIS SF6 gas density online monitoring system to replace the mechanical pointer density sensor will become an inevitable development trend, GIS SF6 gas density online monitoring system will become one of the subsidiary standard configuration of GIS equipment.