Based on the analysis of the vector relation between the neutral point current and zero-sequence current of faulty and normal lines

a detection method of high impedance grounding fault based on the differential current of zero-sequence current projection and neutral point current is proposed. As grounding fault occurs

the fault line passes through grounding point and neutral point of the system to form a basic zero-sequence circuit. Because the neutral point current is resistive

the difference between the projection of zero-sequence current of fault line on neutral point current and the neutral point current is small. However

the zero-sequence current of non-fault line is capacitive

so the difference between the projection of zero-sequence current of non-fault line on neutral point current and the neutral point current is large. Therefore

the ratio method is introduced to detect high impedance grounding fault effectively. Then a further investigation is made about the effects of asymmetric line parameters

asymmetric load and asymmetric voltage of the system on the presented method. Simulative results by PSACD proves that the presented method can reliably detect high resistance grounding fault

which is less affected by various asymmetric conditions

and has high sensitivity and reliability.