AN H V D C CABLE PROTECTION SYSTEM

摘要

An H.V.D.C. cable protection system in which a transmission cablehas a normal polarity with respect to earth determined by a normal power flow direction. In the event of a fault, a reflected voltage surge on the line can in some cases give a 100% reverse polarity voltage on the line, with the result that the cable can be damaged unless it is designed (at significant extra cost) to withstand such voltage reversal. According to the invention a diode rectifier is connected between the lines at each end of the cable in such direction as to be reverse biased in normal operation. A reverse voltage on the line is thus limited to the forward drop of the diode. Since this would produce a very large diode fault current a resistance is incorporated in series with the diode to limit the current even though at a sacrifice of a small reverse voltage.