tailieunhanh - Electrical Power Systems Quality, Second Edition phần 2

Thời lượng biến thể điện áp ngắn Thời lượng điện áp Biến thể điện áp mất cân bằng dạng sóng méo điện áp dao động điện tần số Điều khoản điện chất lượng biến thể nhập nhằng hiện CBEMA và Curves Chương ITI tài liệu tham khảo 3: sụt ÁP vÀ GIÁN ĐOẠN Nguồn sụt và interruptions Ước tính các nguyên tắc Sag | Voltage Sags and Interruptions Voltage Sags and Interruptions 51 causing a voltage sag with duration of more than 1 cycle occurs within the area of vulnerability. However faults outside this area will not cause the voltage to drop below pu. The same discussion applies to the area of vulnerability for ASD loads. The less sensitive the equipment the smaller the area of vulnerability will be and the fewer times sags will cause the equipment to misoperate . Transmission system sag performance evaluation The voltage sag performance for a given customer facility will depend on whether the customer is supplied from the transmission system or from the distribution system. For a customer supplied from the transmission system the voltage sag performance will depend on only the transmission system fault performance. On the other hand for a customer supplied from the distribution system the voltage sag performance will depend on the fault performance on both the transmission and distribution systems. This section discusses procedures to estimate the transmission system contribution to the overall voltage sag performance at a facility. Section focuses on the distribution system contribution to the overall voltage sag performance. Transmission line faults and the subsequent opening of the protective devices rarely cause an interruption for any customer because of the interconnected nature of most modern-day transmission networks. These faults do however cause voltage sags. Depending on the equipment sensitivity the unit may trip off resulting in substantial monetary losses. The ability to estimate the expected voltage sags at an end-user location is therefore very important. Most utilities have detailed short-circuit models of the interconnected transmission system available for programs such as ASPEN One Liner Fig. . These programs can calculate the voltage throughout the system resulting from faults around the system. Many of them can also apply faults at .