Mechanism for steel cylinder overturning stand

Composite type island detection method based on phase deviation and frequency variation

The invention discloses a composite type island detection method based on phase deviation and frequency variation. Firstly, delta theta1 and delta theta2, the motion values of two phase deviations areset, and the condition that delta theta1 is more than delta theta2 is met; when the phase deviation angle of the end voltage of a distributed generator (DG, Distributed Generator), delta theta is more than delta theta1, DG is directly judged as island operation; when delta theta is more than delta theta2 and less than delta theta1, the frequency variation value delta f is introduced as supplementary detection amount, only when the condition that delta theta is more than delta theta2 and delta f is less than delta f1 is met, delta f1 is frequency variation motion value, so that the motion of the detection device is judged as island state; the composite type motion criteria of the island detection are concluded as follows: delta theta is more than delta theta1(1) or delta theta is more thandelta ...

Traveling wave failure distance measurement method for electric power circuit

The invention provides a traveling wave failure distance measurement method for an electric power circuit, which comprises the following steps of: (1) measuring initially, namely measuring time difference delta T that an initial traveling wave surge caused by a failure reaches both ends M and N of the circuit when the circuit fails internally, and solving the distance from a bus at the M end to a failure point F, wherein L is the length of the circuit, v is the propagation velocity of a traveling wave, the delta T is equal to the difference of TM and TN and the distance is used as a reference value; and (2) verifying and correcting, namely measuring time difference delta t between a first forward traveling wave surge of the bus at the M end and a reflection traveling wave surge of the failure point after the failure occurs, and solving the distance from the bus to the failure point F, wherein if delta D which is equal to the absolute value of (DMF-DMF*) is less than or equal to 1 kilometer ...

Composite type island detection method based on phase deviation and frequency variation

The present invention discloses a composite type island detection method based on phase deviation and frequency variation. Firstly, delta theta1 and delta theta2, the motion values of two phase deviations are set, and the condition that delta theta1 is more than delta theta2 is met; when the phase deviation angle of the end voltage of a distributed generator (DG, Distributed Generator), delta theta is more than delta theta1, DG is directly judged as island operation; when delta theta is more than delta theta2 and less than delta theta1, the frequency variation value delta f is introduced as supplementary detection amount, only when the condition that delta theta is more than delta theta2 and delta f is less than delta f1 is met, delta f1 is frequency variation motion value, so that the motion of the detection device is judged as island state; the composite type motion criteria of the island detection are concluded as follows: delta theta is more than delta theta1(1) or delta theta is more ...