Fig. 69:
Formula for calculating the Q filter parameter
Fig. 70:
Formula for calculating the cos ϕ gradient (internal power gradient)
10.4.1.1 Parameters for permanent power limitation
Country-
spec. Set-
tings
Men
u
level
Display/
Setting
Action in this menu/meaning
Power limitation
Check activation
Activate or disable the power limitation.
Maximum apparent
power (S
lim
)
1000 – S
max
[VA]
The apparent power is limited globally to the configured value in VA. As
soon as S
lim
has been configured
,
all of the active and reactive power
control values will use S
lim
as 100% instead of S
max
.
Maximum active power
(P
lim
)
1 – 100 [% S
lim
]
Active power is limited globally to the configured value in % S
lim
.
10.4.2 Soft start up / power ramp-up limiting
A soft start-up function is available to prevent the grid from being negatively impacted by a sudden increase in
feed-in power from the inverters.
When the inverter is activated or switched on, the increase in power is restricted by the set gradient. It is possi-
ble to configure whether the soft start-up should occur every time the device is switched on, only upon initial
start-up each day or only upon start-up after the device has been switched off by grid protection. Due primarily
to the fact that there is the risk that many plants could increase their power levels simultaneously after they
have been switched off by grid protection, a soft start-up is usually only required for start-up after a device has
been switched off by grid protection.
The soft start up is implemented by an absolute power limitation that increases with a continuous gradient up
to the maximum power. The actual power of the inverter may vary freely below this limit due to a possible fluc-
tuation in the available power or the target value, but at no time increases above the absolute power limit.
10.5
Advanced islanding detection
Due to decentralized generation, there is the possibility that a deactivated part of the grid will remain live in an
unintended island due to the balance of load and generation in this part of the grid. The detection of unin-
tended island formation is an important function of decentralized generating units and is related to the preven-
tion of damage to equipment as well as safety of personnel.
Depending on the structure and the operation of the distribution grid several dangers exist:
– In case of maintenance work in a distribution grid, personnel may be placed in danger if the deactivated
part of the grid remains live as an island. This is especially the case if not all safety rules are followed.
– If fast auto-reclosure is used in a distribution grid and the deactivated part of the grid remains live as an is-
land, reclosure will likely happen during phase displacement which might cause damage to rotating ma-
chinery on the grid.
– In the event of a fault in a medium voltage grid, the faulty part of the grid is disconnected. If the fault has a
significant resistance, the deactivated part of a medium-voltage grid remains live as an island. Depending
on the type of fault, but explicitly in case of a fault in the transformer, dangerous medium voltage might be
accessible or even present in low-voltage appliances.
Manual
Specifications | 10
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