For the last equation, the condition t1 > tMin shall also be fulfilled. This practically
means that tMin will be equal to the set t1 value when absolute voltage deviation DA
is equal to ΔU ( relative voltage deviation D is equal to 1). For other values see
figure
283. It should be noted that operating times, shown in the figure 283 are for 30,
60, 90, 120, 150 & 180 seconds settings for t1 and 10 seconds for tMin.
t1=180
t1=150
t1=120
t1=90
t1=60
t1=30
IEC06000488_2_en.vsd
IEC06000488 V2 EN
Figure 283: Inverse time characteristic for TR1ATCC and TR8ATCC
The second time delay, t2, will be used for consecutive commands (commands in the
same direction as the first command). It can have a definite or inverse time
characteristic according to the setting t2Use (Constant/Inverse). Inverse time
characteristic for the second time delay follows the similar formulas as for the first
time delay, but the t2 setting is used instead of t1.
Line voltage drop
The purpose with the line voltage drop compensation is to control the voltage, not at
the power transformer low voltage side, but at a point closer to the load point.
Figure
284 shows the vector diagram for a line modelled as a series impedance with
the voltage U
B
at the LV busbar and voltage U
L
at the load center. The load current on
the line is I
L
, the line resistance and reactance from the station busbar to the load point
are R
L
and X
L
. The angle between the busbar voltage and the current, is j. If all these
parameters are known U
L
can be obtained by simple vector calculation.
Values for R
L
and X
L
are given as settings in primary system ohms. If more than one
line is connected to the LV busbar, an equivalent impedance should be calculated and
given as a parameter setting.
The line voltage drop compensation function can be turned On/Off by the setting
parameter OperationLDC. When it is enabled, the voltage U
L
will be used by the
Section 15 1MRK 502 071-UEN -
Control
554 Generator protection REG670 2.2 IEC and Injection equipment REX060, REX061, REX062
Application manual
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