ABB Relion 670 Series Applications Manual page 370

Section 14
Control
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,
direction. It can have a definite or inverse time characteristic, according to the setting
(Constant/Inverse). For inverse time characteristics larger voltage deviations from the
will result in shorter time delays, limited by the shortest time delay equal to the
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:
=
DA VB VSet
ANSIEQUATION2294 V1 EN-US
DA
=
D
D
V
EQUATION1846-ANSI V1 EN-US
=
tMin
EQUATION1848 V2 EN-US
Where:
DA
D
For the last equation, the condition
will be equal to the set
deviation D is equal to 1). For other values see figure 176. It should be noted that operating times,
shown in the figure
tMin .
364
t1 , is used as a time delay (usually long delay) for the first command in one
-
t
1
D
absolute voltage deviation from the set point
relative voltage deviation in respect to set deadband value
t1 value when absolute voltage deviation DA is equal to ΔV ( relative voltage
176 are for 30, 60, 90, 120, 150 & 180 seconds settings for
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t1 > tMin shall also be fulfilled. This practically means that tMin
1MRK 511 401-UUS F
t1Use
VSet value
tMin setting. This
(Equation 120)
(Equation 121)
(Equation 122)
t1 and 10 seconds for
Bay control REC670
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