On-line Detecting Vacuity For Interrupter Of Vacuum Circuit Breaker

At present, the vacuum switches are used widely in medium voltage network because the vacuum switches have many merits such as capacity of breaking off heavy current and extinguishing arc easily, long working life, maintaining less, repairing less, so the vacuum switches mostly take place the other kinds of switches. The vacuum interrupter is the key opponent of the vacuum switches and the vacuum pressure is one of important parameters of vacuum switches. The vacuity of vacuum interrupter directly determines the performance breaking off circuit and is related to the security of electric power system, but the insulating strength and interrupting current capacity in vacuum extremely depends on vacuum pressure. Only meeting the necessary range of vacuum pressure, the performance of vacuum switches is rendered certain. So studying on the measurement and the online detection technique of vacuum pressure within vacuum interrupter has important meaning not only to theory but also to reality.There are many methods testing and detecting the vacuum pressure of interrupter and the methods are different with the different situation. Every method is applied to specific situation and need differential conditions. Generally these methods are divided into the offline detection, loaded detection and online detection. The online detecting methods that the structures of the vacuum circuit breaker unchanged or no sensors added are wanting and methods and equipments used for online detection are still seldom. The usage of present methods online detecting are limited. The new online detecting method is presented in this paper.In this thesis, the important present measurement methods for vacuity of vacuum interrupters are researched and the measurement principles and the characteristics of these methods are analyzed. On bases of the researches and analyses for measurement methods, a new online detection method for vacuity of vacuum interrupter of vacuum switch equipments is presented. This method principle as follows: When the vacuity of vacuum interrupter of vacuum switch equipments deteriorates to certain degree, that the insulating ability between the closed contacts and the shield reduces lead to discharge between the closed contacts and the shield in vacuum interrupter of vacuum switch equipments, the electric discharge can launch the electromagnetic wave pulse, the relations between the electromagnetic wave pulse and the vacuity of vacuum interrupter can be determined, so the vacuity is determined through the relations. The method based on above mentioned principle that the vacuity is found out by the instrument detecting pulses of electromagnetic waves are proposed in order to vacuum circuit breaker online is monitoring.