| 摘要 |
A single-core electrical power cable for use at 400 kV for example has a relatively high-resistance inner shield located between and insulated from the central core of the cable and its low resistance metallic outer sheath. The inner shield is kept continuous throughout the cable run of installations where, for avoidance of currents circulating in the cable sheath, the sheath continuity is broken at spaced-apart locations. By virtue of such continuity, the inner shield provides a continuous path for surges developed in the cable as the result of lightning strikes or switching operations thereby preventing the development of corresponding high transient overvoltages at the outer cable sheath and particularly at the discontinuities therein. It is thus possible to dispense with the surge voltage limiters previously required to be coupled to the outer cable sheath at intermediate positions of cross-bonded systems. |
