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معمای ترانسفورماتور شماره 81 - نول مشترک
مزایا و معایب ترانس ها با نول مشترک در بخش توزیع چیست؟
نویسنده : هادی - از: ایران
 
#1
ساعت: 11:51 - تاریخ: 26 فروردین 1392
بطور کلی وقتی جدا سازی اتصال زمین دو منبع الکتریکی یک الزام فنی باشد جدا سازی نوترال آنها نیز اجتناب ناپذیر است.

When the electrical system has multiple neutral-to-ground connections, e.g. the main and Standby/Emergency power supplies are separately grounded, the neutrals of the two systems must be separated to assure proper ground fault current sensing. Interconnecting neutrals provide a parallel path for the fault currents and only part of the currents will return on the equipment ground to the source.The other part will return on the neutral through the alternate source grounding to the source and will be seen as normal neutral current by the sensor, thereby, causing incomplete sensing of the total fault current.The sensor can not distinguish between ground fault current and normal neutral current. Similarly the normal unbalanced current in the neutral may bypass the sensor and return on the equipment ground back to the source neutral through the alternate source grounding electrode.Thus, an unbalanced load would effect the sensitivity of the ground fault protection and could cause a trip-out, even though a fault does not exist.
 
نویسنده : حمید - از: فیروزآباد فارس
 
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