This paper studies the effect of a horizontal reference voltage wire, a current lead wire, and the impedance of a voltage probe when measuring a transient voltage on a vertical conductor. A hybrid frequency-time domain (HFTD) method and a finite-different time domain (FDTD) method with the help of VSTL are applied to investigate the effect of the horizontal reference voltage wire, the current lead wire, and the impedance of the voltage probe on measurement at the top of the vertical conductor. The obtained results show that the horizontal reference voltage wire perpendicular to the vertical conductor causes a minor effect, but the input capacitance of the voltage probe affects significantly the voltage measurement. Copyright © 2010 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.