S? d?ng cho h? th?ng ?i?n h? th? khi ngu?n c?p ph? t?i b? gián ?o?n B? chuy?n m?ch t? ??ng, giám sát và chuy?n ??i gi?a hai ngu?n ?i?n Chuy?n m?ch three v? trí I - O - II  – It pressured the reliability by adopting a streamlined sort which is an easy and thoroughly clean form.– T? ??ng kh?i ??ng ho?c d?ng ho?t ??ng ( c?a DG ) khi ngu?n ?