Grounding system of an uninterruptible power system (UPS)

Nowadays an uninterruptible power system (UPS) has been widely used in China to protect various sensitive electrical equipments such as computers, workstations, telecommunications systems, internet data centers, process control systems, etc. The UPS protects them from problems associated with utility power of poor quality, or a complete loss of power. Furthermore, a UPS can also perform other functions such as improving the quality of the power to the critical load. A suitable grounding system should be installed properly for UPS system so that the UPS can function correctly. A grounding system allows circuit protection to clear a ground fault, and provides paths for diverting surge current away from the UPS and for removing undesirable current from the critical load. But in practical applications there used to be some problems which are caused by improper grounding of UPS. This is not a simple subject because grounding techniques depend on several factors such as the configuration of UPS and the type of load connected to the UPS. In addition, another factor to get the grounding system right is knowing whether to design for a separately derived system (SDS). Unfortunately there have been few papers that treat all aspect of UPS grounding system.In this paper the design principle of grounding system for UPS is introduced. The practical grounding systems of UPS used for telecom, DATACOM and computer, etc. are proposed.