Siemens 6MD85, Manual

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Voltage Controller
Overview of Functions
The transformer voltage controller functionality (ANSI 90V) is used to control power transformers (two-
winding transformers, three-winding transformers, grid coupling transformers) and auto transformers using a
motor-operated tap changer. In addition, the voltage control can be used for two-winding transformers
connected in parallel.
The function provides automatic voltage control within a specified voltage range on the secondary side of the
transformers or, as an alternative, at a remote load point (Z compensation or R/X compensation) in the
network. In order to compensate for the voltage variations in the meshed system, use the
LDC-Z
procedure (Z
compensation). For voltage drops on the line, use the
LDC-XandR
procedure (R/X compensation).
The control principle is based on the fact that a higher or lower adjusting command to the tap changer, as a
function of the voltage change (ΔV) per tap, causes a voltage increase or decrease.
The voltage control operates on a tap-for-tap basis and compares the measured actual voltage (Vact) with the
specified target voltage (Vtarget). If the voltage difference is greater than the set bandwidth (B), a higher or
lower adjusting command is sent to the tap changer once the set time delay (T1) has elapsed. Specifying the
time delay (T1) depends on the set controller response (inverse or linear), so as to avoid unnecessary adjusting
commands during brief voltage deviations from the target value and for coordination with other automatic
voltage controllers in the system.
The voltage controller function also monitors the currents on the upper-voltage side and the low-voltage side
of the transformer to block the voltage controller during impermissible operating states (overcurrent/under-
current/undervoltage). The voltage controller function also has limiting values that, in special operating cases,
suppress higher adjusting commands in the case of overvoltage and lower adjusting commands in the case of
undervoltage.
You can also use the voltage controller function for parallel control of up to 8 two-winding transformers in
different groups. You can carry out parallel control based on the Master-Follower method or using circulating
reactive current minimization method. You can find more detailed information about parallel control in
chapter
6.9.3.8 Parallel Control .
Structure of the Function
The Two-winding transformer voltage controller , Three-winding transformer voltage controller, and
Grid coupling transformer voltage controller function groups consist of 5 function blocks. Depending on
the application, the function groups are preconfigured in the relevant application template by the manufac-
turer or can be copied into the corresponding device project during engineering.
The following figure shows, for example, the functional scope of the Two-winding transformer voltage
controller function group.
[dwvolctl-060913-01.vsd, 3, en_US]
Figure 6-116 Structure/Embedding of the Function Group
6.9
6.9.1
6.9.2
Control Functions
6.9 Voltage Controller
450 SIPROTEC 5, High-Voltage Bay Controller, Manual
C53000-G5040-C015-9, Edition 11.2017