| 摘要 |
This invention relates to a method and apparatus of detecting and compens ating for DC residual fault currents on electrical systems. In particular, t he present invention relates to a method and apparatus which is capable of a ccurately detecting one or more parameters of the fault current waveform and generating a compensation factor which compensates for specific pulsed DC f ault components present. In this way, trip sensitivity is optimised for all types of fault current waveforms. In a preferred embodiment, the present inv ention operates by detecting one or more parameters of the encoded fault cur rent waveform and generating a measure of symmetry comparing the mean square d values of negative and positive sections of said encoded fault current wav eform. In use, various bands of the ratio of the mean squared sum of the pos itive and negative sections of said encoded fault current waveform are obtai ned, and a compensation factor is determined from a look-up table stored in a processing means.
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