This paper reviews the effect of a reference voltage wire and a current lead wire when measuring a transient voltage on a vertical conductor. An analytical electromagnetic fields approach has been employed to explain the effect of the voltage reference wire and the current lead wire on voltage measurement. A hybrid electromagnetic-circuit model is applied to investigate the effect of induced voltage on the horizontal reference voltage wire on measurement at the top of a vertical conductor. The results obtained show that the reference voltage wire perpendicular to the vertical conductor and the current lead wire causes a minor effect on the peak value of the measured voltage and current at the top of the vertical conductor and affects the voltage waveform. The estimated surge impedance of a vertical conductor is affected by the configuration of a current lead wire and a voltage reference wire. Additionally, an experimental configuration mitigated electromagnetic coupling is proposed. Copyright © 2010 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.