A finite-difference frequency-domain scheme for simulation of current distributions on three-phase bus bar structures

Summary form only given. A finite-difference frequency-domain (FDFD) scheme is implemented to solve for 60 Hz current distributions in non-segregated phase bus structures commonly used in high voltage connections such as (1) switchgear to switchgear (2) switchgear to transformers and (3) generators to auxiliary compartments. The three-phase bus bars in these applications, normally configured in a side-by-side configuration, carry large currents in close proximity. Thus, the current distributions on the bus bars are simultaneously impacted by the skin effect and the proximity effect, so that simple approximations based solely on the skin effect are inaccurate. Accurate models of the bus bar current distributions are required to design the non-segregated phase bus such that excessive conductor heating is prevented.A FDFD scheme is selected to simulate the bus bar current distributions due to the low-frequency limitation of the commonly-used finite-difference time-domain (FDTD) scheme. Highly resolved structures containing fine grids require very small time-steps in FDTD simulations that make a low-frequency solution impractical. Only the spatial variation of the current is involved in the single frequency FDFD solution, which yields an efficient solution scheme at lowfrequency. The FDFD formulation is implemented as a two-dimensional solution appropriate for the current distributions away from the ends of the bus bars. Maxwell´s equations are manipulated into a modified wave equation for the electric field given the imperfectly conducting and nonmagnetic bus bars that are air-insulated. Simple finite-difference approximations to the spatial derivatives of the governing differential equation are incorporated and continuity of the tangential electric field is enforced at all air-conductor interfaces. A conducting enclosure is assumed for the non-segregated phase bus system. Examples of bus bar current distributions are presented for different geometries of interest. T- e interaction of the proximity and skin effects in the bus bar current distributions are examined for different conductor spacings.