Three Phase Transformer Winding （三相变压器绕组）.pdf

Three Phase Transformer Winding Configurations and Differential Relay Compensation Larry Lawhead, Randy Hamilton, John Horak Basler Electric Company Presented before the 60th Annual Georgia Tech Protective Relay Conference May 2-5, 2006 This page intentionally left blank. Three Phase Transformer Winding Configurations and Differential Relay Compensation Larry Lawhead, Randy Hamilton, John Horak Basler Electric Company Most engineers have some familiarity with two commonly known delta connections that give 0 0 either a +30 or - 30 phase shift of positive sequence voltages and currents, and just these two configurations seem to cause extensive confusion. There are actually many other ways to configure a wye or delta that give other phase shifts, and to further complicate matters, there is the occasional zigzag winding application and the additional confusion over what occurs when CTs are connected in delta. These alternate transformer winding configurations are sometimes referred to by terms such as Dy# or Yy#, or Yd#, Dz#, and Yz#, and where the # can be, seemingly, almost any hour of the clock, hence the term “around the clock” phase shifting is sometimes heard. The paper will review the variety of possible winding configuration and give examples of the nomenclature that is used with them and how these various phase shifts are created. The paper will also show how a transformer differential relay compensates for the effects of the various transformer winding configurations, as well as account for delta CT configurations. Many papers and instruction manuals refer to compensation in terms of phase shifting. This leads engineers to have a vague and misleading underst