Comparison of Neutral Wire Distribution Options for Data Centers

A typical electrical distribution topology used for critical applications involves using a backup generator and an Uninterruptible Power Supply (UPS) system to ensure the continuity of the power supply. When the main low voltage (LV) switchgear is equipped with a 4-pole transfer switch, questions arise as to what happens during a changeover. The UPS and the down-stream loads switch from a TN grounding system to an un-grounded system and may experience some disturbances. This document discusses the potential power quality issues that can arise under this scenario and summarizes and compares different neutral wire distribution alternatives that avoid or minimize the risk of generating power disturbances that can cause interruptions or equipment malfunctions.