The long gap discharge in a plasma display panel has an advantage of high luminous efficacy but has a deficiency of high firing voltage as well. A hump-shape electrode is suggested to reduce the firing voltage of a long gap discharge while maintaining high luminous efficacy. The effects of hump electrodes inserted between two sustain electrodes are investigated by experiment and with a three-dimensional fluid simulation. The experimental results show that hump structure has lower firing and sustain voltage than the conventional long gap structure. A three-dimensional fluid simulation shows that the hump electrode enhances discharge ignition while maintaining the same optical characteristics of the long gap discharge. Also, the hump structure guarantees the addressing reliability with a reduced discharge time lag. (C) 2009 Elsevier B.V. All rights reserved.