Abstract: Multi-stage current operated power supply including linear transformer coupled to AC power lines and provides positive and negative regulated output progressively charged during each half cycle of input current while maintaining ampere-turns balance.

Abstract: A symmetrical component sequence filter which provides a signal responsive to a predetermined sequence quantity of an electrical power system, while using only one phase shift other than 180 degrees. A single reactive element provides the phase shift. A single adjustable resistor calibrates the filter when the reactive element is non-precision. Selecting a precision reactive element eliminates even the single adjustment. The symmetrical component sequence filter enables both a positive and a negative sequence component to be simultaneously derived from common processing circuitry, requiring only one additional reactive element.

Abstract: Apparatus for detecting the presence of subsynchronous current components in an electrical generating or transmission system is disclosed. Input signals, representative respectively of line voltage and current, are conditioned and initially filtered to suppress high frequency noise. The input voltage signal is further limited and filtered to produce a constant amplitude, sinusoid reference. The input signals are then multiplied to yield the subsynchronous current signal components, if any, which undergo further filtration by a bandpass filter circuit. In addition, the detection apparatus is provided with circuit means for insuring protection against overvoltage and current surge conditions.

Abstract: Apparatus for protecting a power system or a portion thereof against the effects of subsynchronous current oscillations is disclosed. A signal representative of or proportional to the subsynchronous current is developed via synchronous modulation and bandpass filter techniques. This signal is fully rectified to produce a waveform from which information can be garnered from both the positive and negative half-cycles.A peak holding and peak status circuit then compares successive peaks of the rectified signal, which circuit is adapted to recognize only those peaks having increasing amplitude. The output of the peak holding and peak status circuit is utilized by three comparator circuits which individually employ differing reference voltage levels for overall evaluation purposes.

Abstract: An input signal supplied to a signal measuring circuit is either amplified or attenuated as necessary to establish the magnitude of the input signal within the defined dynamic range of the measuring circuit and the output signal developed by the measuring circuit is subsequently readjusted through amplification or attenuation to develop an output signal which corresponds to the magnitude of the initial input signal.

Abstract: The disclosure relates to a time-overcurrent relay utilizing successive linear time-current segments which approximate a non-linear, inverse time-current curve the linear segments are determined by subtracting a series of ramp like voltages of increasing magnitudes from a series of bias voltages, each of which is of substantially constant magnitude and which bias voltage magnitudes decrease in sequence by the peak magnitude of the preceding ramp voltage.

Abstract: An automatic gain control circuit functions to adjust the magnitude of an input signal supplied to a measuring circuit to a level within the dynamic range of the measuring circuit while a log-ratio circuit adjusts the magnitude of the output signal from the measuring circuit to the level of the input signal and optimizes the signal-to-noise ratio performance of the measuring circuit.