Behavior In The Event Of A Communication Timeout - Kaco blueplanet 87.0 TL3 M1 WM OD IIF0 Manual

Manual
– 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.
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 in-
dustry is therefore in constant research to develop methods that are fast and reliable and at the same time reli-
ably prevent false tripping.
Enhanced island detection method
Die erweiterte Inselnetzerkennung von KACO new energy, verwendet eine Strategie zur zuverlässigen Erken-
nung der Inselbildung, die auf den unterschiedlichen Eigenschaften eines Verbundnetzes und eines Inselnetzes
basiert und somit eine zuverlässige schnelle Erkennung und Vermeidung von Fehlauslösungen gewährleistet.
An interconnected grid is dominated by rotating machinery, as a consequence frequency is proportional to ac-
tive 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 balance. 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 ROCOF of the grid exceeds the configured disconnection threshold (stage 1) for the configured disconnec-
tion time, the device switches to zero current mode. If the ROCOF of the grid exceeds the configured shutdown
threshold (stage 2) for the configured shutdown time, the device shuts down. In case of an island, this will shut
down the island instantaneously. If the grid stabilizes, what might be the case if the ROCOF event was due to a
short disturbance in the power grid, the inverter will resume normal operation. In the event of active stage 1,
the device switches to zero current mode, and re-starts the infeed after a few 100ms. At stage 2, the device has
shut down and the set reconnection conditions apply.
10.6

Behavior in the event of a communication timeout

NOTE
Communication in the event of a communication timeout
In the event of a communication timeout, the value is queried in the timeout parameter for the reactive power
shift factor cos ϕ [See section 10.1.3} Page 74] , reactive power [See section 10.1.3} Page 74] and active
power [See section 10.2.2} Page 77]. If all values for the timeout are set to 0 seconds, the current functions
are retained without a fault message being issued.
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