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例1,三相负荷不平衡造成开关跳闸。某变电所一低压出线开关多次跳闸。该出线带照明灯。当夜间照明灯全部打开后,工作约半小时开关即跳闸;若只开一部分照明灯,开关不跳闸。此现象说明开关跳闸原因是过负荷而不是出线短路。该出线所用开关为DZ10—100/332开关(带复式脱扣器,脱扣器额定电流Ir为30A),所带全部负荷为33盏GFN—250W钠灯,其起动电流4.5～5A,工作电流3A。若三相负荷平衡的话,每相最大工作电流为11×3=33(A),为Ir的1.1倍,在此电流下,依脱扣器特性,
Example 1, three-phase load imbalance caused by switch tripping. A substation a low-voltage outlet switch multiple trips. The outlet has a light. When the night lights are turned on, the switch will trip in about half an hour. If only part of the lights is on, the switch will not trip. This phenomenon indicates that the switch trip is due to overload rather than a short circuit. The outlet switch for the DZ10-100 / 332 switch (with double trip unit, trip unit rated current Ir is 30A), with a total load of 33 GFN-250W sodium lamp, the starting current 4.5 ~ 5A, operating current 3A . If the three-phase load balancing, then the maximum operating current per phase 11 × 3 = 33 (A), 1.1 times Ir, at this current, according to the release characteristics,