The advantages of shield cable shield grounded at both ends

Thu-01-70


When the control cable for flux bus transient current generated by the layer will be induced, shielding current shielded cable, the flux is produced by the effect of shielding current, flux will link transient current offset the core cable. Assume that the shielding effect ideal, a combination of the two, will cause by the flux core cable shielding layer completely surrounded in zero, shielding layer formed an ideal Faraday cage. This is the same with two short circuited coil of transformer core flux in the ideal, will be zero. Of course, the shielding effect of shielding layer, due to various reasons, can not be completely ideal, therefore, is the core wire shielding in busbar transient current role, will still induces a certain voltage.


The shield grounded at both ends, can reduce the induction voltage transient ground potential rise produced.

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When the 16mm 4 core armoured cable lightning arrester grounding through injection, the substation grounding grid in the impact current increases, potential fluctuation will cause transient, while network considered in grounding resistance will rise temporarily. The determination results of substation grounding potential rise that, compared with the normal AC resistance, resistance to increase by more than 10 times. When the low voltage control cables in the ground potential rise of cable laying nearby, potential fluctuation interference. Therefore, the grounding surge current into the ground potential rise will be possible on the low voltage control circuit insulation cooperation brings the serious influence.


In order to quantitatively estimate the quantity injected when the lightning transient induction caused in the control cable core in the net when, in 30 substations in artificial injection grid small impulse current (100 ~ 4000A) when the measured voltage. Transient voltage of two kinds of cable shielding case determined, a cable is no metal shield, two is a metal shielding and grounding cable ends. Experiments prove that shielded cable with two grounded, transient voltage induced inhibition can be below 10% of the original value, is an effective measure to reduce the disturbance voltage.


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