三相同时刻采样值电流差动保护

Novel Differential Protection Based on Three Phase Simultaneity Sampling Values

采样值差动保护具有对系统谐波不敏感和波形识别等优点,作为一种全新的涌流鉴别方案很快被应用到变压器中。但采样值本身的离散性使其存在轻微故障时灵敏度不足的缺点。该文就如何利用三相电流同时刻采样值构成新的电流差动保护判据进行探讨。新型差动保护计算差动电流和制动电流的瞬时值,充分、合理地利用三相电流在单个采样时刻的有效信息进行幅值计算,进而构造差动判据。显然该新型差动保护兼有两种差动保护优势。理论分析和动模试验表明,这种差动保护方案具有数据窗短、可靠性高、波形识别能力强、不受频率偏差影响的优点。

The sample differential protection has many excellent characteristics, For example, it can perform perfectly without being effected by the harmonics in the net and it also has the ability to identify wave shapes. As a new scheme for distinguishing the inrush, it has been applied in the transformer protection. But for the dispersing of sample values, it may do not operate in tiny faults with heavy load, So this paper takes the lead in proposing a novel differential criterion scheme based on three phase instantaneous sample values. It implements the differential and resistant currents according to every sample values and gets a full but reasonable use of the sample information at each point to calculate the amplitude, Then the differential criterion is made. It is evidently that novel scheme obtains both excellences of the above two differential ones. The results of the theoretical analysis and dynamic simulating tests show that the new scheme has many merits such as short data window, high security, powerful ability to distinguish the wave shape, strong adaptability of the frequency change.