Disturbances in low-voltage control circuits in substations and power plants occur due to lightning or switching surges. Adequate protection of electronic devices in low-voltage control circuits requires the capacity to predict surge phenomena and to evaluate the effectiveness of protection methodologies. In this paper, we present and validate a technique to represent twisted-wire pairs, which are commonly used in control circuits, for surge simulations using the Finite-difference time-domain method combined with the Agrawal et al. model.