Installation Guide

© 2016 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
U
0
U
0
U
0
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 (4Ω), 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