Siemens SINAMICS S120 System Manual page 107

Island grid with special topologies
Grid without circuit breaker
If, in an individual case, the circuit breaker between the Active Line Module/Active Interface
module and grid can be eliminated, or if the circuit breaker is not controlled from the
SINAMICS system, and it can be guaranteed that the voltage is the same at both sides of
the switch using the appropriate external systems, then island grid operation can also be
implemented without having to use a 2nd VSM.
Then, only the voltage measured values of the VSM at the Active Interface Module are
available. Contrary to the factory setting, this especially means
p5487[0] = r3661
p5487[1] = r3662.
Grid without isolating transformer
An isolating transformer is always required between an Active Line Module/Active Interface
Module and an island grid. The transformer can also be eliminated, if, in the island grid, an N
conductor is not required, and all loads/consumers and cables in the island grid are designed
for the pulse-frequency potential steps of the particular grid with respect to ground potential.
Further, for the filter monitoring (p3678) an inductance with uk ≥ 5 % is required between the
filter and the grid. The transformer can also be replaced by a reactor, for example. Without
filter monitoring, it is not permissible to clear short-circuits and p5458[1] must be set = 0.01 s.
These conditions must be checked on a case-by-case basis. If necessary, please contact
customer support.
The transformer data identification steps (p5480 = 11, 12) are no longer possible. If the
default values for the DC component control (p5492, p5436) are not suitable, then suitable
settings must be individually determined based on the island grid properties.
Note
When parameterizing the island grid, for operation without a transformer, a 1:1 transformer
must be selected (p5486[0] = p0210).
Danger to life due to fire when the insulation in the island grid is overloaded when an
isolating transformer is not used
Overloaded insulation of loads and cables in the island grid as a result of pulse-frequency
potential steps in the kV range can cause electric shock or fire.
• Carefully ensure that the loads/consumers and cables in the island grid have been
Grid infeed
System Manual, 04/2015, A5E03347436A
DANGER
designed for pulse-frequency potential steps in the kV range with respect to ground
potential.
7.6 Commissioning the grid transformer
Commissioning
107