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protection 27 by allowing the grid operators to define its own Low-Voltage Ride-Through
(LVRT) curve for generators, as defined by local or national grid codes. The LVRT curve
can be defined accurately according to the requirements by setting the appropriate time-
voltage coordinates.
The function contains a blocking functionality. 27RT can be blocked with the
BLOCK
input. Blocking resets timers and outputs.
4.5.7.4
Operation principle
The function can be enabled and disabled with the
Operation
setting. The corresponding
parameter values are "Enable" and "Disable".
The operation of 27RT is described using a module diagram. All modules in the diagram
are explained in the next sections.
V_A_AB
V_C_CA
V_B_BC
BLOCK
TRIP
PICKUP
LVRT
curve
monitoring
V
1
GUID-4B9C3BE5-5E7E-4877-8AE7-05C142CDD6CF V1 EN
Figure 328:
Functional module diagram
LVRT curve monitoring
LVRT curve monitoring starts with detection of undervoltage. Undervoltage detection
depends on
Voltage selection
setting. All selectable options are based on fundamental
frequency components.
Function uses phase-to-ground voltages when
Voltage selection
is set to “Highest Ph-to-
E” or “Lowest Ph-to-E” and phase-to-phase voltages when
Voltage selection
is set to
“Highest Ph-to-Ph” or “Lowest Ph-to-Ph”.
When the
Voltage selection
setting is set to “Highest Ph-to-E”, “Lowest Ph-to-E”,
“Highest Ph-to-Ph” or “Lowest Ph-to-Ph”, the measured three-phase voltages are
compared phase-wise to the set
Voltage pickup value
. If the measured value is lower than
the set
Voltage pickup value
setting in number of phases equal to that set
Num of pickup
phases
, the
PICKUP
output is activated.
The setting options available for
Num of pickup phases
are “Exactly 1 of 3”, "Exactly 2 of
3", and “Exactly 3 of 3”, which are different from conventional setting options available
in other functions. For example,
Num of pickup phases
is set to "Exactly 2 of 3", any two
voltages should drop below
Voltage pickup value
within one cycle network for the
1MAC059074-MB A
Section 4
Protection functions
615 series ANSI
659
Technical Manual
Содержание Relion 615 series
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