When subjected to high voltages between opened contacts,vacuum interrupters may emit X-rays.In order to ensure that these are of an acceptable level,vacuum interrupters should comply with the limits for X-ray emission and the test procedures to be carried out to verify this based on relevant standards and specifications.In this paper,a comprehensive experimental study has been performed for 126 kV vacuum interrupters used in a transmission system to understand the X-radiation level and its influence by three main parameters,namely applied power-frequency voltage,contact gap and power-frequency voltage conditioning.The radiation instrument is an FJ347 radiometer and the X-radiation dose was measured at the power-frequency test voltage.These tests demonstrated that the X-radiation emission level for a 126 kV vacuum interrupter did not exceed the following:5 μSv per hour at a rated voltage of 126 kV and 150 μSv per hour at a power-frequency voltage of 230 kV at 1 m distance.The X-radiation dose increased with the applied power-frequency voltage increasing and decreased with the contact gap increasing.The Xradiation dose for 126 kV vacuum interrupters decreased by 57%after the conditioning procedure with a certain power-frequency voltage.During the conditioning procedure,the average value of the X-radiation dose was 4.49 mSv,which means if a professional conditions 180 interrupters per year,it will be safe at the 6.4 m distance.
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