| 摘要 |
A transformer differential relay monitors the current flowing through the primary and secondary windings of a power transformer and disconnects the transformer from a power source feeding the transformer whenever the magnitudes of these currents indicate a fault condition in the transformer. First and second current transformer generate primary and secondary winding voltage signals representative of the magnitude of the current flowing through the power transformer primary and secondary windings, respectively. A solid state restraint signal generator is responsive to the primary and secondary winding voltage signals and generates a restraint signal representative of the magnitude of the larger of the primary and secondary winding currents, respectively, at each measurement instant. An operate signal generator is responsive to the primary and secondary winding voltage signals and generates an operate signal representative of the magnitude of the vector sum of the currents flowing through the power transformer primary and secondary windings. Finally, means are provided for disconnecting the power transformer from the power source when the magnitude of the operate signal operates above a predetermined percentage of the restraint signal.
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