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.