Advanced Islanding Detection - Kaco blueplanet 3.0TL3 Series Manual

Some grid connection rules insist that the agreed reactive power be supplied from every operating point of the plant
without a reduction in the actual active power. Considering the fact that all KACO TL3 inverters have a semi-circular P-Q
operating range, a reduction in the active power is, however, required during operation at maximum active power be-
cause an apparent power reserve is not available. By adjusting P
to establish an apparent power reserve and ensure that the agreed reactive power can be delivered from any active
power operating point. [See figure 61] [} Page 68] Displays the appropriate P-Q operating range with a required example
active power of 48% of the maximum apparent power of the plant or 43% of the maximum active power of the plant.
Fig. 61: P-Q operating range with limited active power (Qmax=Smax≠Pmax) for PV inverters
10.4.2 Soft start-up / Power rampup
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 possible to con-
figure 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 protec-
tion, 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 fluctuation 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 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:
ž 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.
ž 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.
ž 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.
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, the maximum active power can be restricted in order
lim
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