真空断路器选相合闸空载变压器的试验研究

Experimental Study on the Phase Control Closing of Vacuum Circuit Breakers for No-load Transformer

电力变压器是电网中至关重要的元件,并且是变电站中最昂贵的设备。如果空载时突然把变压器投入电网,由于变压器的非线性,在合闸瞬间会产生很大的励磁涌流,其幅值可达稳态时的几十倍或更高。通常励磁涌流的衰减速度要比短路电流的衰减速度更慢,在上述高幅值的励磁涌流下,很容易引起变压器差动保护装置误动、绕组机械应力增大以及电能质量降低等问题,而真空断路器的选相合闸能很好的解决这个问题。文中在某大功率试验站的6 kV网络试验回路上采用12 kV快速真空开关进行了空载变压器的合闸试验,试验中测量了真空断路器随机合闸、普通选相合闸和检测剩磁选相合闸空载变压器这3种情况下的励磁涌流,测得的涌流大小用于验证选相合闸的效果。试验结果表明与随机合闸相比,选相合闸能够显著减小励磁涌流,检测剩磁选相合闸与普通选相合闸相比更能显著减小励磁涌流,但是即使采用了检测剩磁选相合闸的方法,真空断路器的预击穿特性也对选相合闸效果存在影响。

Power transformer is a crucial component in power system, and it is the most expensive equipment in substation. The nonlinear characteristics of transformer would result in significant magnetizing inrush current when closing a no-load transformer, and the current amplitude would reach up to dozens of times of the steady state current. In general, the decay rate of magnetizing inrush current is slower than that of short circuit current. Thus the high magnitude magnetizing inrush current would cause the maloperation of protection equipment in the transformer, the increase in mechanical stress of the windings, and the deterioration of the power quality. Fortunately, phase control closing of vacuum circuit breaker is a satisfactory solution to this problem. In this study, a test of closing no-load transformer by a 12 kV vacuum circuit breaker was conducted in the 6 kV direct test circuit of CEPRI. The magnetizing inrush current during random closing, common phase control closinz, and phase control closing with calculating remanence was measured in order to verify the effect of phase control closing. The results indicate that the phase control closing, especially the phase control closing with calculating remanence, is effective in reducing the magnetizing inrush current compared with random closing. However, the prestrike characteristic of a vacuum circuit breaker influences the effect of phase control closing even though the phase control closing with calculating remanence is employed.