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在国内外标准中,不接地厂用电系统对地电容电流的限值数值为≤10 A。标准中限制电容电流是为了加快电弧熄灭,降低电弧过电压的持续时间,而并不是防止电弧的产生。电弧过电压的危害与过电压的倍数、发生频率和持续的时间有关。当系统设备存在绝缘薄弱点时,电弧过电压可能导致电气设备中绝缘薄弱点击穿,造成多点短路事故。电缆接头、附件以及电动机的绕组都是绝缘薄弱点。设置消弧线圈可中和系统的电容性接地电流,达到快速消弧的目的;使用浇注母线可显著降低输电线路的对地电容电流值,对设备更安全。
In domestic and foreign standards, ungrounded plant power system capacitive current limit value is ≤ 10A. The standard limit capacitor current is to speed up the arc extinguishing, reduce the duration of the arc over-voltage, and not to prevent the arc from generating. The hazards of arc overvoltage and overvoltage multiples, the frequency of occurrence and the duration of the. When there is a weak point in the insulation of the system equipment, the over-voltage of the arc may lead to the breakdown of the insulation in the electrical equipment and cause multiple short-circuit accidents. Cable joints, accessories, and motor windings are weak points of insulation. Set the arc suppression coil can neutralize the capacitive ground current of the system, to achieve the purpose of rapid arc suppression; use of cast bus can significantly reduce the transmission line capacitance to ground current value of the device more secure.