In the process of making medium-voltage switches oil-free, vacuum switches have been widely used due to their arc-extinguishing performance. However, the deterioration of the vacuum degree in the interrupter is a gradual process. When the vacuum degree falls below the allowable value, the breaking capacity of the switch will significantly decrease. Relevant standards have clear provisions for the vacuum degree limits of vacuum interrupters; for example, the 12kV class usually requires no less than 1.33×10^-2 Pa. Design and selection personnel need to pay attention to: how can the vacuum degree data inside the interrupter be accurately obtained without dismantling the switch?
Problem 1: Why are traditional measurement methods difficult to meet on-site needs?
Traditional methods such as the magnetron discharge method require dismantling the interrupter, or the power-frequency withstand voltage method can only make a qualitative judgment. Dismantling not only increases outage time but may also introduce assembly errors. The power-frequency withstand voltage method cannot provide quantitative values, making it difficult to determine whether the vacuum degree is close to the critical value. During design and selection, the lack of quantitative data may lead to unexpected failure of the switch during its life cycle.
Solution: Technical response of the HDZK-Ⅳ vacuum switch vacuum degree tester
This instrument adopts the magnetron discharge method and can quantitatively measure the vacuum degree inside the interrupter of various types of vacuum switches. The measurement range covers 9.999×10^-1 Pa to 9.999×10^-5 Pa. During on-site measurement, there is no need to dismantle the vacuum switch. An excitation coil is directly applied to the interrupter, and the vacuum degree value is calculated through the corresponding relationship between ion current and vacuum degree. The test results are accurate and reliable, avoiding the additional risks caused by dismantling.
Problem 2: How can on-site operation and data management balance efficiency?
Design and selection personnel often need to compare the vacuum degree trends of multiple switches or provide a basis for life assessment. If the instrument is complex to operate and data cannot be exported, work efficiency will be affected.
Solution: Human-machine interaction and data interface design
The HDZK-Ⅳ adopts LCD Chinese character display, and the operation steps are simplified. The instrument can save, print, and view test data. It is equipped with an RS232 communication interface and can be connected to a computer to realize functions such as vacuum degree-ion current curve download and life estimation. The instrument is lightweight and easy to carry, making it suitable for on-site use. For selection personnel, it is recommended to measure and record the vacuum degree before the switch is put into operation and during regular maintenance, and to establish trend files so as to judge the remaining life of the interrupter.
In the selection and maintenance stages, paying attention to the operability of vacuum degree testing and the continuity of data helps improve the operational reliability of medium-voltage switches.
