Method and apparatus for testing the excitation characteristic of current transformer

摘要

This disclosure relates to the field of current transformers, for testing the excitation characteristic of a current transformer is disclosed. The method comprise applying alternately positive and negative DC voltages across terminals of secondary winding of a CT to be tested and acquiring a secondary current; constructing a mathematical model of the relationship between the secondary current and a root mean square (rms) equivalent voltage at rated frequency of the CT from the relationship between a magnetic flux of a secondary winding iron-core of the CT and the rms equivalent voltage; and generating an excitation characteristic curve according to the mathematical model. The method and apparatus of the embodiments may test CTs requiring lower testing voltage as well as CTs with knee-point up to tens of kV by supplying a relatively low voltage and power, which makes the embodiments widely applicable.

主权项

1. A method for testing excitation characteristic of a current transformer (CT), characterized in that the method comprises the steps of:
applying alternately positive and negative DC voltages across terminals of secondary winding of a CT to be tested, and acquiring a secondary current; constructing a mathematical model of a relationship between the secondary current and a root mean square (rms) equivalent voltage at rated frequency of the CT from a relationship between a magnetic flux of a secondary winding iron-core of the CT and the rms equivalent voltage; and generating an excitation characteristic curve according to the mathematical model, wherein the mathematical model is:Uc=2⁢π⁢⁢f2*{∫0t⁢[U⁡(t)-Rct*Ict⁡(t)]⁢ⅆt+Φ⁡(0)} where Uc is the rms equivalent voltage at the rated frequency of the CT, f is the rated frequency of the CT, U(t) is an amplitude of the DC voltage applied to the terminals of the secondary winding at time t, Rct is a DC resistance of the secondary winding, Ict(t) is the secondary current acquired at time t, and φ(0) is the magnetic flux of the secondary winding iron-core when time t=0, wherein the step of acquiring the secondary current each time the positive or negative DC voltage is applied across the terminals of the secondary winding of the CT to be tested comprises: setting a target secondary current; applying the positive or negative DC voltage across the terminals of the secondary winding of the CT to be tested; and acquiring the secondary current, and once the acquired secondary current reaches the target secondary current, the positive or negative DC voltage is stopped from being applied to the terminals of the secondary winding of the CT to be tested.