Electricity: electrical systems and devices – Safety and protection of systems and devices – With phase sequence network analyzer
Patent
1986-12-23
1988-02-02
Scott, J. R.
Electricity: electrical systems and devices
Safety and protection of systems and devices
With phase sequence network analyzer
307127, 324 86, 324108, H02H 326
Patent
active
047231890
ABSTRACT:
A negative sequence occurring in a polyphase power system control including a continuous wave frequency transducer causes a second harmonic to be generated which for a 60 Hz system comprises a 120 Hz signal. In a preferred embodiment of the invention, the continuous wave frequency transducer includes an active 120 Hz notch filter having one stage which provides a component of the 120 Hz second harmonic. This signal is coupled to a second harmonic detector implemented by a semiconductor diode connected to the output of an operational amplifier. The detector diode is coupled to one input of a comparator circuit whose other input is coupled to a selectable DC reference signal. The comparator operates to generate a fault indicating signal indicative of a negative sequence when the output from the second harmonic detector exceeds the reference. The fault indicating signal is thereafter converted to a digital type signal which can be utilized by external utilization circuitry such as a system control circuit or a diagnostic subsystem.
REFERENCES:
patent: 4146913 (1979-03-01), Sun
patent: 4210948 (1980-07-01), Waltz
patent: 4342062 (1982-07-01), Hodges
patent: 4447843 (1984-05-01), Massey
patent: 4479160 (1984-10-01), Stacey
Larsen Einar V.
Shiflett Russel G.
General Electric Company
Jennings Derick S.
Renner Arnold E.
Scott J. R.
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