Separation methods utilizing high-frequency and high-voltage pulsed DC electric fields are extensively used in the oil and petroleum industries, where the occurrence of water-in-oil dispersions is highly unwelcome due to physical constraints, as well as the high maintenance costs required to treat these dispersions. This paper reports the studies of the effects of externally applied electric field parameters (e.g. voltage magnitude, electric frequency, and duty ratio), and operating parameters (e.g. operating temperature and operating time) on the dehydration process of steam-assisted gravity drainage (SAGD) produced ultra-heavy oil in a high-frequency pulsed electrical field. The investigations were performed in the DTS-4C airtight oil dehydration apparatus. The results illustrated that finding the optimum values of electric and operating parameters are of great significance to make a considerable increase of the dehydration efficiency. The optimum conditions obtained were as follows: voltage magnitude, 5.5 kV; electric frequency, 4.0 kHz; duty ratio, 0.5; operating temperature, 120 degrees C; and operating time, 3.0 h. Under the above conditions, the dehydration efficiency and post-electric-dehydration moisture content were 97.81% and 037 wt%, respectively, which are acceptable for refineries, and the dehydration power and electric current were positively correlated with the change of water content which influences the emulsion conductivity. (C) 2017 Elsevier B.V. All rights reserved.