Created by: Glen Zhu | Updated Date: January 07th, 2025
Type 2 Surge Protection Device (SPD) SLP40-275/3S+1 widely used for TT power supply systems, it is made of MOV (Metal Oxide Varistor) and GDT (Gas Discharge Tube), take this SPD for example is the most typical representative.
This article describes measure the uninstalled surge protection device (SPD) and the on-site surge protection device (SPD), there are many similarities between them, mainly in the measurement of uninstalled surge protection device (SPD).
The appearance surface of the surge protection device (SPD) no cracks and burn marks, and the identification of the surge protective device should be complete and clear.
Visual window should indicate ‘Green’, not half red and half green, or red.
Special measuring tools: Surge protection device tester SPD888
The Surge protection device tester SPD888 is mainly designed for on-site testing of surge protection devices. It is used to test the basic parameters of the core components in these devices – voltage limiting components or voltage switch components:
Turn off the upstream dedicated disconnector (MCCB or MCB) of SPD, use ‘Surge protection device tester SPD888’ to connect ‘L’ terminal and ‘N’ terminal to measure the MOV’s voltage and leakage current.
Note: For SPDs connected in 1P+N (1+1), 3P+N (3+1) configuration, as shown in diagram (b), test wires should be connected to L1, L2, L3 to N (note: do not connect to PE).
Turn off the upstream dedicated disconnector (MCCB or MCB) of SPD, use ‘Surge protection device tester SPD888’ to connect ‘L’ terminal and ‘PE’ terminal to measure the MOV’s voltage and leakage current.
Note: For SPDs connected in 2P (2+0), 3P (3+0), 4P (4+0) configuration, as shown in diagram (a), test wires should be connected to L1, L2, L3 to PE.
This check is divided into three parts:
How to select MOV (Metal Oxide Varistor)
Max. continuous operating voltage Uc (V~) of SPD | Range of varistor voltage (V~) | Leakage current (μA) | α |
275V AC | 430Vdc ± 10% the value is between 387Vdc ~ 473Vdc | < 20 μA | the value is between 50~60 |
Tab 1
According to the tab 1, MOV module of SLP40-275/0 selected LKD brand MOV 34S431K, the estimated voltage is 430V DC, we need set the ‘CJ1001 varistor DC parameter meter’ before check it.
Set the ‘current range’: 20μA
Set the ‘voltage rate’: 75%
Set the ‘voltage range’: 600V
Set the ‘constant current’: 1
Set the ‘operating mode’: Auto
Set the ‘direction’: Positive
When use the ‘CJ1001 varistor DC parameter meter’ to check the MOV’s voltage and leakage current, if the voltage is between 387V and 473V, the leakage current is less than 20μA, the value of α is between 45 and 60, the result is judged to be qualified.
How to select GDT (Gas Discharge Tube)
Max. continuous operating voltage Uc (V~) of SPD | Range of varistor voltage (V~) |
255V AC | 600Vdc ± 20% the value is between 480Vdc ~ 720Vdc |
Tab 2
According to the tab 2, GDT module of SLP40-275/NPE selected Vactech brand GDT PS6C600D, the estimated voltage is 600V DC, we need set the ‘CJ1009B GDT parameter meter’ before check it.
Set the ‘raising speed’: 1kV/S
Set the ‘voltage range’: 2000V
When use the ‘CJ1009B GDT parameter meter’ to check the GDT’s voltage, if the voltage is between 480Vdc and 720Vdc, the result is judged to be qualified.
The SPD Base with floating switch is made of PCB board, microswitch and transmission device.
The working principle of surge protection device’s floating switch
The state of floating switch (remote control):
Common application:
Set the ‘multimeter’, turn the function dial to ‘alarm’
Connect the test leads with ‘11’ and ‘12’, ‘multimeter’ sound an alarm, it is judged to be qualified.
Any of pluggable module of SPD damaged, visual window indicate ‘red’, connect the test leads with ‘11’ and ‘14’, ‘multimeter’ sound an alarm, it is judged to be qualified.
LSP’s reliable surge protection devices (SPDs) are designed to meet the protection needs of installations against lightning and surges. Contact our Experts!
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