| 摘要 |
PCT No. PCT/DE95/00098 Sec. 371 Date Nov. 12, 1996 Sec. 102(e) Date Nov. 12, 1996 PCT Filed Jan. 18, 1995 PCT Pub. No. WO95/20765 PCT Pub. Date Aug. 3, 1995A method for measuring the current in an AC power transmission network, where a measurement quantity is obtained by means of a current transformer and digital samples are converted. To prevent faulty detection of the current due to a decaying DC component of the current transformer, two initial auxiliary measurement quantities that are normal to one another are formed from the digital samples by means of at least two FIR filters, and together with two additional auxiliary measurement quantities that are normal to each other, are used to produce a measured value corresponding to the amplitude of the current. The additional auxiliary measurement quantities are produced from samples formed from an older measurement quantity obtained earlier by a quarter period of the current to be measured. The differential angle is formed from the two measurement quantities. An output signal is generated from the two measured values in an evaluation device when the measured values exceed preset threshold values. |
