磁阀式饱和电流互感器的理论研究

普通高压在线取能电流互感器(CT)在一次大电流状态下铁心饱和,二次绕组感应电势畸变为尖峰脉冲电压,饱和程度越深,脉冲宽度越窄,导致难以稳定获取较大功率的能量。笔者通过对饱和机理深入分析,揭示出普通CT饱和过程中铁心磁导率变化和一次电流变化失配是内在原因,并由此提出了铁心饱和控制方法———区间配合法。基于该方法,通过对磁阀式饱和CT的工作原理、数学模型、工作特性及实验分析,表明磁阀式饱和CT可以实现铁心饱和过程中CT有效磁导率变化与一次电流变化的配合特性,能够满足一次电流大于200A时1W功率电源的在线取能要求。

Research on the Theory of Magnetic Valve Type Saturable Current Transformer

The core of conventional current transformer used for on-line acquiring-energy in a high voltage measurement system is saturated under the condition of high-level primary current, and then spike pulse voltage is induced in secondary winding. The duration of pulse voltage becomes shorter with increasing core saturation. It is difficult in acquiring enough energy due to the short duration of pulse voltage. By analyzing magnetic saturation mechanism, it is found that the essential cause is attributed to the mismatch between the change of core permeability and the primary current during the core saturation. Therefore, a current-interval-match method for controlling the core saturation is presented. Based on this method, a novel magnetic valve type saturable current transformer was introduced. The analysis of its operation principle, mathematic model, operating characteristics and tests shows that, by using the magnetic-valve type saturable current transformer, the match characteristics between the changes of core effective permeability and primary current during core saturation may be achieved, and the requirements of 1 W power supply for on-line acquiring-energy can be met when primary current value is over 200 A.