Investigation of aging procedure of vacuum circuit breakers used in wind farms

Abstract

Wind energy as an affordable and clean source has increasingly penetrated power networks. Vacuum circuit breaker (VCB) owing to high-rated operation-frequency, long service life, and the fast operation speed is of the main protection options in wind farms. Several incidents such as prestrike, restrike, and current chopping happening over the lifetime of VCBs might cause erosion in the contacts or a change in the pressure. This paper presents the applicability of a hybrid-approach on real-time assessment of the erosion and pressure in VCB based on the field emission current level and restrike frequency in a standard three-phase network including wind turbines. Interaction amongst the prominent parameters such as field emission current, arc voltage, vacuum pressure, and erosion rate is scrutinized in a three-phase mode associated with a healthy and a defective VCB. The results reemphasize the applicability of the approach in online condition monitoring of VCBs in a real network. It is indicated that one phase evaluation could result in an imprecise estimation of the diagnostic features. It has been revealed that the worst deterioration rate is dealt with in the first interrupted phase. While the erosion rate of the first clearing pole is twice as high as the other phases in a healthy breaker, it would be eight times in a defective VCB. Furthermore, it is deduced that a VCB with a high operation frequency and subject to more restrikes is more likely to be aged. It is deduced that the erosion leads to a decrease in the interruption capability of high-frequency current, and a lengthier interruption. In addition, it is comprehended that VCBs connected to wind turbines are aged faster than what we expect in conventional networks.