| 摘要 |
PROBLEM TO BE SOLVED: To coordinate time in removing a fault and eliminate unnecessary operation even if the fault or a developing fault from backward to frontward occurs under a sound condition. SOLUTION: This digital directional distance relay periodically samples a plurality of electric quantities of a power system to be protected with respect to voltage and current at the same time; prepares a mho element M of directional discrimination, a reactance element X of range measurement, and a blinder element R using the respective electric quantities converted into digital quantities; detects a system fault point from the operating discrimination of the elements; and discriminates whether the fault point stays in a particular operating area for a fixed time or not. The relay further consists of a first means 11 for determining that the M-element is inoperative and the X-element and R-element are operative, a second means 12 for determining whether the operative condition of the first means continued for a fixed time or more to be established or not, a third means 13 for determining whether the setting values of the X-element and R-element are equal to a prescribed value or more, and a means 14 for delaying the operating output time of the X-element when the determined result of the second or third means is satisfied.
|
