| 摘要 |
1492181 Detecting faults in D.C. transmission systems; HVDC transmission systems HITACHI Ltd ELECTRIC POWER DEVELOPMENT CO Ltd and TOKYO SHIBAURA ELECTRIC CO Ltd 30 Oct 1974 [2 Nov 1973] 47017/74 Headings H2K and H2F A fault detecting arrangement in a H.V.D.C. transmission system comprises a first detector LD 1 providing a signal when the current at the rectifier-end BA of the transmission line TL rises above a reference level, a second detector LD<SP>1</SP> 2 providing a signal when the current at the inverter-end BB falls below a reference level, and a coincidence circuit AND 1 providing a fault indication when the two signals occur simultaneously. Since the D.C. line may normally be worked in either direction, it is preferable to provide both a current increase and a current decrease detector at each end, two coincidence circuits, e.g. AND 1 , AND 2 , then being necessary. These coincidence circuits may be duplicated, i.e. a pair at each end, and be coupled to the opposite end via a separate transmission link. The reference levels may be fixed values. Alternatively, if the normal line current varies, each detector compares the instantaneous line current with the value of the line current a short time previously, thereby detecting only sudden changes in value. |
