交叉互联高压电缆护层保护器故障对同回路两端护层电流相量差的影响

The influence of sheath voltage limiter faults on sheath current phasor difference between the two ends in the same sheath loop of high voltage cables is the theoretical base of the fault diagnosis criteria. At device level, the equivalent circuit of sheath voltage limiter consists of a parallel capacitance and nonlinear resistance is modelled in this paper. At system level, a mathematical and physical model of cross-bounded cable system under normal and faulted condition is formulated, then the transfer function between the fault impedance of sheath voltage limiter and the phasor difference of the sheath current measured on the two solid grounding points in the same sheath loop is derived therefore. The results of the simulation on 110 kV cable system show that not the faulted sheath voltage limiter can be distinguished by the sheath current phasor difference under metallic grounding faults. Phase of the sheath current phasor difference is sensitive to metallic and low resistance grounding faults, whilst its the phasor deviation of the sheath current phasor difference between 100 ohms grounding fault in left and right sheath voltage limiter and normal condition range from 17.9º~24.9ºor 33.4º~51.1º; and 9.4º~24.9 or 9.4º~24.9ºunder 216 ohms grounding fault. Besides, unequal length of minor sections and phase current fluctuation have significant influence on the sheath current phasor difference, and the grounding resistance and phase voltage fluctuation have insignificant impact on the sheath current phasor difference.