加装零序电压互感器圈的消谐型电压互感器由三相主电压互感器TV1和串接在中性点的零序电压互感器TV0二部分组成,采用零序电压互感器消除谐振。该消谐装置要求TV0的开口三角绕组闭合,零序电压U0从TV0的二次侧取得。当单相接地时, TV每相励磁感抗为Xm=XTv1+3XTv0(XTv1为TV1的漏抗;凡XTv0为TV0励磁感抗)。
The harmonic elimination voltage transformer with zero sequence voltage transformer coil is composed of three-phase main voltage transformer TV1 and zero sequence voltage transformer TV0 connected in series at neutral point. The zero sequence voltage transformer is used to eliminate resonance. The harmonic elimination device requires the opening triangle winding of TV0 to be closed, and the zero sequence voltage U0 is obtained from the secondary side of TV0. When single-phase grounding occurs, the excitation inductance of each phase of TV is Xm = XTv1 + 3XTv0 (XTv1 is the leakage reactance of TV1; whereas XTv0 is the excitation inductance of TV0).
由于XTv1很小,可略,故Xm≈3 XTv0,即零序电压绝大部分降落在TV0上,一般的外激发不能使TV,进人饱和区,从而使谐振难以产生。此外,TV0高压绕的直流电阻约为10k欧,对谐振有强烈的阻尼作用,对涌流有限制作用。此种消谐型TV的消谐作用也仅对自身有效,热容量也有限。
Because XTv1 is very small, it can be omitted, so Xm_3 XTv0, that is, most of the zero-sequence voltage falls on TV0. The general external excitation can not make TV enter the saturated region, so that resonance is difficult to produce. In addition, the DC resistance of TV0 high voltage winding is about 10 kOH, which has strong damping effect on resonance and limited inrush current. The harmonic elimination effect of this kind of harmonic elimination TV is only effective for itself, and its heat capacity is limited.