10.4.2.1 Parameter for power ramp
4
1
2
3
4
Power ramp
NOTE: The power ramp allows a moderate increase of the Perform-
ance possible
Gradient
1 – 600 [% / min]
Gradient of power limit. The maximum power limit increase to 100% of
nominal power with the gradient specified.
After every connect
Soft start ramp up is activated for every connection of the inverter to
the grid
After first connect
Soft start ramp up is activated for the first connection of the inverter to
the grid on a particular day or after complete reboot of the inverter (AC
and DC disconnected)
After grid error
Soft start ramp up is activated for connection of the inverter to the grid
after trip of the internal interface protection or via the external grid pro-
tection port (Powador-protect)
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 uninten-
ded island due to the balance of load and generation in this part of the grid. The detection of unintended island formation
is an important function of decentralized generating units and is related to the prevention 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 island, reclos-
ure will likely happen during phase displacement which might cause damage to rotating machinery 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.
Especially for the last example very fast disconnection of the generating units to cause collapse of the forming island is
necessary. At the same time any island formation detection method may cause false tripping. The industry is therefore in
constant research to develop methods that are fast and reliable and at the same time reliably prevent false tripping.
Enhanced island detection method
The enhanced island detection of KACO new energy, employs a strategy to reliably detect island formation that is based
on the characteristic differences between an interconnected grid and an islanded grid, thus ensuring reliable fast detec-
tion and prevention of false tripping.
An interconnected grid is dominated by rotating machinery, as a consequence frequency is proportional to active power
balance and voltage is proportional to reactive power balance. In contrast an islanded grid behaves like a resonant circuit,
as a consequence frequency is proportional to reactive power balance and voltage is proportional to active power bal-
ance. The active enhanced island detection method detects this difference by monitoring the behaviour of the grid. The
enhanced island detection is monitoring the natural fluctuation of the grid frequency and injects a minimal reactive
power proportional to the rate of change of frequency. In the moment of formation of an island the connected power
systems is closing a positive feedback loop what allows the inverter to detect the changed situation and to disconnect. In
case of formation of an island, the inverter disconnects within some 100 ms, well below 1000 ms.
The number of parallel inverters does not affect the reliability of this function.
This method also ensures that the impact on the distribution grid is kept to a minimum.
In normal operation no effects on harmonic content, flicker and grid stability are detected.
This detection method is combined with a two stage passive rate of change of frequency (ROCOF) observation. If the RO-
COF of the grid exceeds the configured disconnection threshold (stage 1) for the configured disconnection time, the
device switches to zero current mode. If the ROCOF of the grid exceeds the configured shutdown threshold (stage 2) for
KACO blueplanet gridsave 50.0TL3-S
Page 68
EN