t s
k A
B
U U
U
C
D
E
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GUID-6E9DC0FE-7457-4317-9480-8CCC6D63AB35 V2 EN (Equation 106)
t[s] operate time in seconds
A the set value of
Curve parameter A
B the set value of
Curve parameter B
C the set value of
Curve parameter C
D the set value of
Curve parameter D
E the set value of
Curve parameter E
U measured voltage
U> the set value of
Start value
k the set value of
Time multiplier
11.3.1.3 IDMT curve saturation of overvoltage protection
For the overvoltage IDMT mode of operation, the integration of the operate time
does not start until the voltage exceeds the value of Start value. To cope with
discontinuity characteristics of the curve, a specific parameter for saturating the
equation to a fixed value is created. The Curve Sat Relative setting is the parameter
and it is given in percents compared to Start value. For example, due to the curve
equation B and C, the characteristics equation output is saturated in such a way that
when the input voltages are in the range of Start value to Curve Sat Relative in
percent over Start value, the equation uses Start value * (1.0 + Curve Sat Relative /
100 ) for the measured voltage. Although, the curve A has no discontinuities when
the ratio U/U> exceeds the unity, Curve Sat Relative is also set for it. The Curve
Sat Relative setting for curves A, B and C is 2.0 percent. However, it should be
noted that the user must carefully calculate the curve characteristics concerning the
discontinuities in the curve when the programmable curve equation is used. Thus,
the Curve Sat Relative parameter gives another degree of freedom to move the
inverse curve on the voltage ratio axis and it effectively sets the maximum operate
time for the IDMT curve because for the voltage ratio values affecting by this
setting, the operation time is fixed, that is, the definite time, depending on the
parameters but no longer the voltage.
11.3.2 IDMT curves for undervoltage protection
In the inverse-time modes, the operate time depends on the momentary value of the
voltage, the lower the voltage, the faster the operate time. The operate time
calculation or integration starts immediately when the voltage goes below the set
value of the Start value setting and the START output is activated.
The OPERATE output of the component is activated when the cumulative sum of
the integrator calculating the undervoltage situation exceeds the value set by the
Section 11 1YHT530004D05 D
General function block features
834 615 series
Technical Manual
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