Led Lighting Spd Design Installation Guide Page 13 LED Lighting SPD Design & Installation Guide

2015 Littelfuse LED Lighting SPD Module Design and Installation Guide www.littelfuse.com LED Lighting Surge Protection Modules Design and Installation Guide - Loss of Secondary Neutral. A broken neutral shifts its potential away and may cause a 1.73 ( 3) over-voltage at Line-to-Neutral in the worst case. L1 L3 N U0 L2 L1 L3 L2 N 1 N (A) Normal (B) Lost of neutral Figure 12. Lost-of-neutral in 3-phase electric power system TOV caused by faults in the high/medium voltage system When a distribution transformer (for example, 10kV to 380V, as shown in Figure 13) has a short-circuit fault at the high-voltage side (10kV) Line-to-Ground, it generates a high fault current (Id=300A, 200ms duration) through grounding resistor Re (4 ), which in turn elevates the Neutral potential (Ue=1200V) at the low-voltage side. The TOV test thus intends to simulate a ground fault at the high-voltage system by injecting 1200V into N-G at the SPD module in the low-voltage system. 100kV 10kV 380V Id=300A Ue=1200V Re (4-ohm) grounding resistor Figure 13. Line-to-ground fault in high/medium voltage transformer Temporary over-voltages affect SPDs when a short-circuit fault happens in a power network. It is important for SPDs to meet both the UL 1449 and IEC 61643-11 standards to ensure their safety and reliability. The addition of thermally protected MOVs in SPDs not only suppresses transient voltages but also ensures their own safety against overheating and catching fire. Over-voltage Testing in UL 1449 and IEC 61643-11 (continued) 13

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