ABB REG670 Applications Manual page 559

1MRK 502 071-UEN -
Generator protection REG670 2.2 IEC and Injection equipment REX060, REX061, REX062
Application manual
setting FSDMode. The ULOWER command, in fast step down mode, is issued with
the settable time delay tFSD.
The measured RMS magnitude of the busbar voltage U
value BUSVOLT under Main menu/Test/Function status/Control/
TransformerVoltageControl(ATCC,90)/TR1ATCC:x/TR8ATCC:x.
Time characteristic
The time characteristic defines the time that elapses between the moment when
measured voltage exceeds the deadband interval until the appropriate URAISE or
ULOWER command is initiated.
The purpose of the time delay is to prevent unnecessary load tap changer operations
caused by temporary voltage fluctuations and to coordinate load tap changer
operations in radial networks in order to limit the number of load tap changer
operations. This can be done by setting a longer time delay closer to the consumer and
shorter time delays higher up in the system.
The first time delay, t1, is used as a time delay (usually long delay) for the first
command in one direction. It can have a definite or inverse time characteristic,
according to the setting t1Use (Constant/Inverse). For inverse time characteristics
larger voltage deviations from the USet value will result in shorter time delays, limited
by the shortest time delay equal to the tMin setting. This setting should be coordinated
with the tap changer mechanism operation time.
Constant (definite) time delay is independent of the voltage deviation.
The inverse time characteristic for the first time delay follows the formulas:
IECEQUATION2294 V2 EN
DA
=
D
D
U
EQUATION1986 V1 EN
=
t
tMin
1
D
EQUATION1848 V2 EN
Where:
DA absolute voltage deviation from the set point
D relative voltage deviation in respect to set deadband value
Section 15
Control
is shown on the local HMI as
B
(Equation 268)
(Equation 269)
(Equation 270)
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