ABB ACS580-04 - MID-Point-Grounded Delta Systems

The table below shows the line-to-ground voltages in relation to the line-to-line voltage
for each grounding system.
Electrical power system typeU
L3-G
U
L2-G
U
L1-G
U
L-L
Symmetrically grounded TN system (TN-S
system)
0.58·X0.58·X0.58·XX
Corner-grounded delta system (nonsymmet-
rical)
01.0·X1.0·XX
Midpoint-grounded delta system (nonsymmet-
rical)
0.5·X0.5·X0.866·XX
IT systems (ungrounded or high-resistance-
grounded [>30 ohms]) nonsymmetrical
Varying level
versus time
Varying level
versus time
Varying level
versus time
X
TT system (the protective earth connection
for the consumer is provided by a local earth
electrode, and there is another independently
installed at the generator)
Varying level
versus time
Varying level
versus time
Varying level
versus time
X
When to disconnect ground-to-phase varistor: TN-S, IT,
corner-grounded delta and mid-point-grounded delta
systems
Symmetrically grounded TN systems (TN-S systems)
Do not disconnect the ground-to-phase varistor.
PE
L2
L3
L1
N
Corner-grounded delta systems
Do not disconnect the ground-to-phase varistor.
PE
L3
L2
L1
282 Ground-to-phase varistor disconnecting instructions – IEC, not North America