Calculation and Restraining Method for Circulating Current of Single Core High Voltage Cable

Excessive ground circular current on the metal sheath of high-voltage cable will cause massive loss which can reduce cable transmission efficiency and safe operating lifetime. In this paper, high-voltage cable under cross-bonded grounding mode is taken as the research object. According to the model and equivalent circuit of cross-bonded grounding mode of high-voltage cable, the calculation model of ground circular current is established. Based on the model, the variations of ground circular current and grounding current are calculated and analyzed when the cable phase spacing, segment length or load current changes. The ground circular current suppression methods of connecting series resistance and inductance on the metal sheath and series grounding resistance and compensation inductance at the terminal are proposed. Furthermore, the calculation models of ground circular current suppression methods and the balanced restraint effects on ground circular current are considered respectively. Obtained results reveal that the ground circular current will generate when one factor of the phase spacing, segment length and load current of the cable changes, and the relationship between the ground circular current and unbalanced coefficient is approximately linear. The grounding current will generate when the load current of cable changes, and the relationship between the grounding current and unbalanced coefficient is approximately linear. However, grounding current will not change when the segment or phase spacing of cable changes. The ground circular current suppression methods of connecting series resistance, inductance and compensation inductance have remarkable inhibitory effects on ground circular current caused by the factor of cable segment or phase spacing. The ground circular current suppression method of connecting grounding series resistance has significant inhibitory effects on ground circular current produced by the factor of load current.