✍ Scribed by A.J. Kellogg; L.P. Singh; G.K. Dubey
No coin nor oath required. For personal study only.
Polyphase distance relaying using solid state components has been accepted in general as a secondary protection for EHV/ UHF lines. It is not surprising that in developed countries solid state relaying has gained popularity as the primary means of protection with 100% discrimination and reliability. The older schemes using rectifier bridge phase detectors are not so sensitive and are also slow in operation, especially near boundary conditions. This paper deals "with a new relaying scheme, using digital circuits with CMOS logic, which does not use a separate starting unit, nor an electromechanical unit for zone changing. The present relaying scheme with mho and elliptic starting characteristics can give modified mho characteristics with blinders or a quadrilateral characteristic by simply changing the measuring circuit and signal processing unit. This relay has been designed, fabricated and tested on a 'dynamic test bench' which has also been designed and fabricated in this laboratory. It is expected that this relaying scheme may prove to be better than the existing ones.
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