Research Of Calibration Device For Transformer Pressure Release Valve

Pressure release valve is the main non-electric protection device of transformer and needs to be calibrated regularly.The existing calibration methods of pressure release valves are mainly off-line and on-line detection.In the process of on-line detection,the larger problem of human impacts cause great damage to equipment and lower measurement accuracy.While off-line detection equipment requires different devices for release valves with different calibers and opening pressures,and the accuracy of the device will be reduced after long-term usage.To overcome these problems,a set of pressure release valve calibration system has been developed.The research contents and results are as follows:(1)The designed calibration system is particularly suitable for pressure release valves with opening pressure ranging from 25 kPa~ 200 kPa and calibers of 50,80 and 130 mm.The uncertainty of the device is less than or equal to 1.67 kPa.It basically meets the requirements of the industry.Three test tanks with 30 L,30 L and 90 L capacities are connected by butterfly valve D71 X seal to meet the requirements of the test tanks with volumes of 30 L,60L and 150 L for calibration,and 5L test tank are used to measure the sealing pressures of release valves;and to ensures the accuracy of measurements,digital pressure controllers PPC3 and FLUKE are selected for verification of pressure transmitters(2)The software part of the calibration device includes VC++ and access database by which the device can realize real-time monitoring of data and save detected data to the database to generate calibration certificates.The historical data can also be queried through conditions.(3)The device is verified to meet the requirements by testing standard device in the calibration device of pressure release valve.Then,the calibration system of pressure release valve is used to carry out calibration experiments,and the accuracy of the test results is verified by analyzing the experimental data.According to the test data of pressure release valve,such as corresponding opening pressure 138 kPa for 130 mm caliber,corresponding opening pressure 69 kPa for 80 mm caliber and corresponding opening pressure 55 kPa for 50 mm caliber,the uncertainty of calibration system is evaluated.Finally,the synthetic and extended uncertainties of the aging opening pressure,opening pressure and closing pressure of each pressure release valve are all less than 1.67 kPa,which meet the uncertainty requirements of the system pressure.