Method and system for identifying the direction of a fault.

摘要

In direction identification for a close-in fault when the voltage becomes very small, direction of the fault is determined from the discriminant D given by:<MathDetails id="matha01"><MathText><![CDATA[ <img id="ia01" file="imga0001.tif" wi="31" he="10" img-content="math" img-format="tif" inline="no" /> ]]></MathText></MathDetails>where v<Sub>k1</Sub>, v<Sub>k3</Sub> represent sample values of the voltage at time points k1, k3, and i<Sub>k2</Sub>, i<Sub>k4</Sub> represent either sample values of the current at time points k2, k4 or such sample values minum current component values corresponding to pre-fault power flow.Here,k1=n-m-M;k2=n:k3=n-m;k4=n-M, where m represents the number of sampling operations over an interval equal to a multiple of half cycle of the system frequency, M represents an integer, and n represents a sampling time point. A signal for use, e.g., as a condition for tripping a circuit breaker is produced when the fault is found to be in the direction of the protection zone.