Method for judging internal and external faults of direct-current line area of hybrid direct-current power transmission system

Abstract

The invention discloses a method for judging internal and external faults of a direct-current line area of a hybrid direct-current power transmission system. The method comprises the steps of 1 takinga time data window after a protection starting element is started, and calculating a fault component, a line-mode voltage fault component, a line-mode current fault component and a line-mode voltagereverse traveling wave therein; 2 calculating a sampling point ks and a minimum value of a reverse traveling wave change rate in two points after the sampling point ks, and recording the minimum valueas dub / dt_m<3>; 3 setting a threshold value th1, comparing the threshold value th1 with -dub / dt_m <3>, and judging whether the fault is a line external fault or not; 4 finding out a sampling point corresponding to a reverse traveling wave descending end moment caused by the fault first traveling wave through point-by-point comparison; 5 calculating a descending amplitude value A under the fault first traveling wave; 6 calculating a reverse traveling wave variable quantity S in the remaining data window; 7 calculating the ratio R of the reverse traveling wave variable quantity to the decreasing amplitude value under the fault first traveling wave; and 8 setting a threshold value th2, comparing the threshold value th2 with R, and judging whether the fault is a fault in the line area. The method is higher in sensitivity, and can distinguish high-resistance faults.

Description

technical field

[0001] The invention belongs to the technical field of power systems, and relates to a method for distinguishing faults inside and outside the DC line area of ​​a hybrid direct current transmission system. Background technique

[0002] The traditional HVDC transmission technology based on grid-commutated converters (LCCs) has been maturely applied to long-distance large-capacity power transmission and power networking. However, since the converter components use semi-controlled power electronic device thyristors, the system completely relies on the AC power grid to operate, and the inverter station is prone to commutation failure, especially in the multi-infeed DC system, it is easy to cause cascade commutation of multiple converter stations failure with serious consequences. The voltage source converter (VSC) high-voltage direct current transmission based on fully controlled devices does not rely on the AC grid voltage to support the operation, and can supp...

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