| 摘要 |
The method is for impedance protection, with a given function area in a R - X plane for release with an internal fault within the function area, and the prevent release with an interference detection which can be initiated by an external fault, where the external fault corresponds to a faulty impedance on a power line. The faulty impedance resistance and reactance values are determined, and this involves access to sampled values on the power line phase currents (I) and phase voltage (U) and a line model for building a model voltage (Um) for the power line. The method is applied to each of the measurement coil phases to earth and between all phases. After an interference detection each measured voltage sample Ui is set out as Ui = a.Umi + b.Ifi in which "a" is equal to the ratio between the sought reactance XF and the power line reactance XI, where "b" is equal to the sought resistance RF and where IFi is a given projection on the faulty current. |
