Then the method for zero sequence current direction protection is proposed based on the character parameter of zero sequence active current.

Since the success rate of faulty line selection based on single criterion for single-phase earthing fault in non-solidly earthed network is normally low,a new comprehensive faulty line selection equipment is proposed which based on the first half transient wave and active component direction of zero-sequence current.

The paper Presents the principle of selective leakage protection based on zero sequence current direction.

This paper analyzes the basic principle of Sel587 differential protection device and elaborates the influence of zero sequence current .

In order to reduce influences of varieties of operation conditions of power systems and differences of grounded fault type on the protecting range of the instantaneous zero sequence current protections of transmission lines,a feasible method for realizing the adaptive instantaneous zero sequence current protections was put forward.

Comparative analysis on zero-sequence current of Y,y_(no) and D,y_(n11) transformers;

Analysis of transient process of zero-sequence current during single-phase reclosure;

Polarity check of zero-sequence current and voltage based on microcomputer protection;

Starting with the traits of zero order impedance and the relationship between zero order current and zero order impedance,analyzes the main differences of electric traits of power cables and aerial lines and the disadvantages of applying power cables into the traditional grounded protection.

On the basis of analyzing the law of variation of the zero order current, the zero order voltage and the zero order power in the isolated neutral system, a synthetic criteria principle of selecting the grounded fault line according to three criterias at the same time was put forward.