Abstract: A microprocessor-based transformer monitoring system to provide continuous on-line monitoring and analysis of transformer operation. The transformer monitoring system periodically monitors various parameters related to transformer load and condition. Maximum, minimum, and instantaneous values of the parameters are stored and analzyed. To perform the analysis, a hierarchy of thresholds is associated with each parameter. When a parameter exceeds any one of the thresholds, a response is produced by the transformer monitoring system. The type of response depends on the level of the exceeded threshold in the hierarchy. The range of response produced by the transformer monitoring system includes: continuing normal periodic data collection and analysis, increasing the rate of data collection and analysis, recommending an on-site physical check of the monitored transformer, reducing transformer load, and taking the transformer off line.

Abstract: A protective relay for detecting power arcing faults on a low-voltage spot network. The protective relay can monitor the voltage difference between each phase conductor, the voltage difference between each phase conductor and the neutral conductor, or the current on each phase conductor. Using one of these three sets of values, the protective relay first filters the input signal so that only frequencies indicative of a power arcing fault on the low-voltage spot network are analyzed. The signals passed by the filter are amplified, rectified, and averaged and the peak of each signal detected. If the peak has a duration longer than a predetermined value, a fault indication is provided.

Abstract: A method and an arrangement of apparatus is provided for remotely detecting the existence of a failed fuse of a brushless exciter rotor's rotating rectifier assembly. A conducting fuse produces a magnetic field which is sensed by elements on a stationary structure. A signal corresponding to the conducting status of each fuse is synchronized to the rotational speed of the brushless exciter rotor by means of a preselected oscillator frequency and the status of each individual fuse is retained and displayed until the next inspection of that fuse. Alarm circuitry enables automatic detection of a failed fuse and shutdown in the event of multiple fuse failures. Since this method looks for the instance of current through each fuse, it operates in a fail-safe manner.

Abstract: Signal conditioning apparatus for reducing the noise frequencies of a speed sensing means signal being fed into a compensating means for compensating the output of a synchronous generator for the effect of torsional oscillation between masses in the main AC generator system. The signal conditioning apparatus includes two speed sensing transducers mounted 180.degree. apart on opposite sides of a tooth gear wheel and summing the two FM output signals from the transducers to eliminate odd harmonics of the synchronous frequency in FM noise due to eccentricity. The preferred embodiment of the invention reduces the remaining noise from the sensed speed signal by the use of a three-pole Butterworth low-pass filter in combination with a notch filter tuned to the turbine-generator synchronous frequency to thereby reduce the unwanted noise to a large degree while providing a minimal phase shift to the sensed speed signal.

Abstract: A transducer is utilized to convert the eccentricity of a turbine shaft into a sinusoidal electrical voltage signal having a given frequency, amplitude and a DC bias. This electrical signal is provided to a circuit which periodically measures the maximum and minimum peaks of the sinusoidal signal. The frequency at which the latter measurements occur is related to the frequency of the sinusoidal input signal. The maximum and minimum levels of magnitude are stored periodically as DC levels and subtracted from each other to determine the absolute value of eccentricity. In addition the stored minimum value is compared with the sinusoidal signal to reduce the DC bias of the sinusoidal signal to a point where the negative peaks thereof are at zero.

Abstract: An analog simulator for simulating the mechanical resilience, mass and damping characteristics of a turbine-generator system. The aforementioned parameters are represented by inductance, capacitance and resistance in the simulating system. Electrical power at the output of a generator is sensed by a power transducer and is provided as input to the simulating system. The power is a measure of the torque on the shaft of the generator. The simulating system computes the torsional oscillations between rotating members of the turbine-generator system and provides electrical output signals which are related to the magnitudes and frequencies of the various computed torsional oscillations. The signals are provided to indicating means such as counters, strip recorders and oscillographs for recording the timing, magnitude, and frequency of the various torsional oscillations.

Abstract: A dynamic stabilizer which includes a voltage generator connected in series with the output terminals of a synchronous AC generator provides compensation for voltages produced by the main AC synchronous machine which compensation is provided to overcome the effects of torsional oscillation between masses in the main AC generator system. Torsional oscillations may exist between the masses of turbines driving the AC generator, the exciter mass for the AC generator, and the mass of the rotor of the generator. Shaft angular velocity is sensed and provided to a frequency discriminating filter since the speed is proportional to the torsional oscillation and since a reference signal is provided to the frequency discriminating filter, the frequency discriminating filter provides an output signal which is proportional to the reference signal plus and minus the frequency of the torsional oscillation. This signal is provided to the previously named series connected generator where a 180.degree.