Ground-to-phase varistor
disconnecting instructions – IEC, not
North America
Contents of this chapter
This chapter describes when and how to disconnect the ground-to-phase varistor. It
gives guidelines for identifying power system types.
Identifying the grounding system of the electrical power
network
WARNING!
Only a qualified electrical professional may do the work instructed in this
section. Depending on the installation site, the work may even be categorized
as live working. Continue only if you are an electrical professional certified for
the work. Obey the local regulations. If you ignore them, injury or death can
occur.
To identify the grounding system, examine the supply transformer connection. See
the applicable electrical diagrams of the building. If that is not possible, measure these
voltages at the distribution board, and use the table to define the grounding system
type.
1. input voltage line to line (U
L-L
)
2. input voltage line 1 to ground (U
L1-G
)
3. input voltage line 2 to ground (U
L2-G
)
4. input voltage line 3 to ground (U
L3-G
).
28
Ground-to-phase varistor disconnecting instructions – IEC, not North America 281
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