Analysis on the weak current and strong magnetic problem of north-west 330 kV lines and its countermeasure

This paper analyzes a maloperation event of longitudinal zero-sequence protection in north-west 330 kV lines, caused by zero-sequence mutual inductance between lines. By deeply analyzing the link between power network structure and maloperation of longitudinal zero-sequence protection from theoretical analysis and quantitative analysis, it sums up behaviors of longitudinal zero-sequence protection under different running situations of double-circuit lines, concludes that the reason for maloperation of protection is weak current and strong magnetic contact of lines, and points out that the necessary condition for maloperation is the reverse of zero-sequence voltage on both sides. In order to solve the weak current and strong magnetic problem, zero-sequence direction components based on fault type are used instead of zero-sequence direction components. Recording data analysis proves the effectiveness and accuracy of this measure.