Grid Monitoring Anti-Islanding - Siemens SINAMICS S120 System Manual

NOTICE
Damage to other grid components as a result of overvoltage
Without using additional monitoring functions, the dynamic grid support can mean that even
when a subgrid is completely isolated from the power grid (unintentional creation of an
island grid), PWM/pulsed operation of the Active Line module in the disconnected subgrid is
maintained.
It is especially important to note that the shutdown conditions previously mentioned
regarding converter self-protection do not prevent AC overvoltages and frequency changes
occurring in the remaining grid formed if high ohmic grid faults occur; these can possibly
mean that other components in the subgrid either malfunction or are damaged.
As a consequence, when activating the dynamic grid support, using suitable supplementary
measures it must be guaranteed that the voltage and frequency limits are maintained in
each individual application scenario.
• Using the "Grid monitoring" function, the function module already provides suitable
• Alternatively, you can implement grid and plant protection, for example using DCC in the
Difference to normal operation
In normal operation, a severe grid fault (thresholds for tripping A06205 are exceeded) will
disable the pulses as well as the boost mode, until the grid has been restored. Injection of
active or reactive current to the network is therefore not possible while the fault is present.
By evaluating the alarm bits r3405.2 or re-parameterizing alarm A06205 into a fault, it is also
possible to achieve a fast safety shutdown in the event of grid faults.
5.3.3.2

Grid monitoring anti-islanding

The "Grid monitoring anti-islanding" function allows an active island grid detection to be
implemented (anti-islanding).
If the power generating system feeds into a power grid, then it is possible that the connection
to the grid is interrupted. This disconnection can either be deliberate (e.g. a subgrid is tripped
due to overload or if work is being carried out on the system) or inadvertently (e.g. sudden
cable interruption in the case of a storm or construction work). An island grid is created if
there are loads between the power generating system and the point of disconnection.
This island grid is undesirable and unstable as there is no grid control. In order to protect
personnel and to facilitate normal restoration of the grid, the power generating system must
identify that an island grid has been formed (anti-islanding detection), and must shut down
the grid infeed.
Grid infeed
System Manual, 04/2015, A5E03347436A
internal monitoring functions. To do this, activate the grid monitoring with p5540ff, and
suitably parameterize the function (see Commissioning of dynamic grid support
(Page 123)).
Control Unit, in an external control or using an autonomous protection system.
Function modules
5.3 Description of the function modules
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