| 摘要 |
PURPOSE:To spot a short-circuit with high precision even in case of the short-circuiting of the whole line regardless whether in a balanced or an unbalanced state by deciding on a positive-phase voltage and a positive-phase current from three line voltages and line currents based upon measured values and arithmetic values, and further calculating a specific virtual phase voltage and calculating reactance from the result. CONSTITUTION:Two line voltages and line currents of three-phase high-voltage distribution lines R, S, and T are measured through transformers CT1-CT4 and current transformers PT1-PT4 and applied to a CPU through an A/D converter ADC to determine three line voltages and line currents. Then, the positive-phase voltage and positive-phase current are calculated by a symmetric coordinate method from those voltages and currents, and the reactance is calculated from the positive-phase current and the virtual phase voltage obtained by dividing the positive-phase voltage by three and delaying the phase by pi/6 (Rad). This reactance is divided by the reactance of the line per unit length to perform spotting from a power transmission side to the short-circuited point P with high precision even in case of the short-circuiting of the whole line regardless of whether in the balanced and unbalanced states.
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