Operation of relays from carrier-current coupling capacitors and capacitance transformer bushings

APPLICATION of carrier current communication to transmission lines required the development of coupling capacitors. These coupling capacitors may be used also in combination with transformers to obtain potential from the transmission line. This potential will be suitable for the operation of certain instruments and relays, depending upon burden and accuracy requirements. By the addition of suitable chokes, the coupling capacitors may be used also for carrier current communication. It is the purpose of this paper to describe briefly these coupling capacitors, and to point out means for utilizing them for the purpose of obtaining potential for relaying operation, and to call attention to some applications.