| 摘要 |
<p>A protective relay circuit. An electrical system signal quantity is monitored and applied to a filter and to a bipolar threshold device in parallel with the filter. The bipolar threshold device has a zero output signal level as long as the magnitude of the monitored signal is less than some predetermined value. When the monitored signal exceeds the predetermined value, the output of the bipolar threshold device will be substantially equal to the monitored signal level minus the predetermined value. The output of the filter and the output of the bipolar threshold device are combined in a summing amplifier to provide a signal for controlling the trip coil of a circuit breaker. When the circuit is use in an overcurrent or overvoltage protective relay, the combined signal is rectified and applied to a level detector which provides the signal for controlling the trip coil of the circuit breaker. When the circuit is used in a distance or directional relay, the phase of the combined signal as compared to the phase of a second monitored signal determines the generation of the signal for controlling the trip coil of the circuit breaker.</p> |
