| 摘要 |
A method of detecting an abrupt variation in a periodic electrical quantity, where a criterion for the occurrence of the abrupt variation is formed from samples of the periodic quantity. To be able to carry out such a method in such a way that the abrupt variations in the periodic quantity can be detected with a high sensitivity, the periodic quantity is weighted in an FIR filter with a transfer function with a double zero position at the nominal frequency; the output signal of the FIR filter is monitored for whether it reaches a threshold indicating that an abrupt variation in the periodic quantity has occurred.
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