In order to use a Rogowski coil for high-accuracy measurement of ac current (up to 20 A at power supply frequency, with an aimed uncertainty of 100 ppm), all influencing quantities and their contributions should be recognized and analyzed. The same theoretical basis can be applied if the use of such a transducer is planned for much higher currents and/or frequencies. Therefore, this paper gives the analysis of the partial influence due to the angle of the primary conductor relative to the secondary coil, with nonhomogeneous density of secondary turns. The measured deviation of mutual inductance showed agreement with the results of theoretical considerations, which show that careful construction of this sensor can provide the required accuracy.