Power quality mitigation measures for advanced building facilities

Like other power systems in the world, most of the voltage dips in Hong Kong are caused by thunderstorms, lightning, vegetation intrusion, third party interference and heavy load switching. In some cases, voltage dip may lead to interruption of major advanced building facilities inside the building like tripping and sudden stoppage of chiller plant and lift. A number of analysis and tests were conducted to verify the ride-through capability for building facilities such as building management system (BMS) and lift in developing a practical and sustainable solution. The ride-through solution for BMS is a successful story that involves cost effective investment for improving the PQ compatibility of the susceptible equipment. Some lifts may also trip during voltage dip. Although most modern lifts are equipped with auto-restart, there were still cases where the feature was unable to function and resulted in shut-in-lift situation. Unless the lift was locked off by the operation of the safety gear in which attention by lift maintenance personnel was necessary, in most other cases the situation could be improved with suitable mitigation measures. These include remote alarm, post-voltage-dip-operation [1] and regenerative braking features. This paper describes the major initiatives formulated to meet this PQ challenge for advanced building facilities such as BMS and lift. The mitigation measures for BMS and lift combating voltage dip incident will also be presented.