Siemens 6MD85, Manual

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Figure 6-131 Logic Blockings
1) If transformer differential protection is available
2) If a current measurement is available
3) If parallel proxys are available (max. 7)
If assignment of the tap changer for the transformer side is available, the current of the upper-voltage side is
also monitored and the differential-protection pickup automatically blocks the voltage controller.
Additional Blockings for the Three-Winding Transformer Voltage Controller
The blockings described in the above sections also apply to the controlled winding of the three-winding trans-
former. In addition, the blockings for undervoltage, minimum voltage, and overcurrent are used for the meas-
urands of the uncontrolled side.
Additional Blockings for the Grid Coupling Transformer Voltage Controller
For voltage control in grid coupling transformers, the voltages and currents of both windings are always used
for the blockings.
Parallel Control
General
The parallel control of 2 or more power transformers is intended to increase the electrical throughput or short-
circuit power at a power-system node. An additional reason for the parallel control of transformers is a reserve
in case of a failure of a transformer.
If power peaks are to be expected in the power system, several transformers can be connected in parallel on
different busbars. This allows several feeders to be supplied simultaneously. You can control up to 8 trans-
formers in parallel in a group. The measured and status values are analyzed via the IEC 61850 GOOSE commu-
nication.
If the tap positions differ for the transformers used, thus creating a different transformation ratio, the no-load
voltages on the low-voltage side are different. A circulating current flows via the transformers, the so-called
circulating reactive current. As the transformer impedance consists mainly of leakage inductance, the current
is inductive. These currents can lead to an overload of the transformer.
The parallel control is intended for two-winding transformers. For the parallel control, additionally instantiate
the function Parallel controller. You need an additional function block
ParallelProxy
for each of the
transformers connected in parallel. The 1st
ParallelProxy
is preinstantiated. For a configuration with 8
transformers working in parallel, you can instantiate a maximum of 7
ParallelProxy
. The exchange of the
necessary information takes place via this proxy. 8 transformers can be configured to a maximum of 4 groups.
6.9.3.8
Control Functions
6.9 Voltage Controller
SIPROTEC 5, High-Voltage Bay Controller, Manual 465
C53000-G5040-C015-9, Edition 11.2017