Abstract-This paper presents a modified segmentation method that can be used in the fast algorithm to calculate the transfer impedance of an arbitrarily shaped power-bus at any port location. Being different from conventional studies that only discuss two rectangular shapes, the present study extends the segmentation method to cascade any number of power planes that contain triangular and rectangular shapes. The transfer impedance of an irregular power-bus is obtained by cascading a few rectangular and isosceles triangular power-buses. Good agreement between simulate and experimental results which indicates the validity of the modified segmentation method.