7SR242 Duobias Description Of Operation
©2010 Siemens Protection Devices Limited Chapter 1 Page 37 of 52
3.10 Voltage Protection: Over Fluxing (24)
Optionally, three over fluxing elements are provided – 2 x 24DT and 1 x 24IT Char elements.
The 24DT Elements have a DTL characteristic. 24DT Setting sets the pick-up level and 24DT Delay the follower
time delay. An output is given if the Volts/Hertz ratio is above setting for the duration of the delay. The 24DT-n
Hysteresis setting allows the user to vary the pick-up/drop-off ratio for the element.
The 24IT Element has a user definable shape.
24Xn Point Setting sets the over fluxing (V/f) level for up to 7 user definable points.
24Yn Point Setting sets the operate time for each of the defined points.
The 24IT Reset setting can apply a, definite time delayed reset.
X-(V/f)
X0
Y0
X6
Y6
X0, Y0 point
defines
curve pick-up
X6, Y6 point
defines
curve cut-off
X
X
X
X
X
X
X
Straight-line
between points
Figure 3-16 Inverse Over-fluxing Characteristic (24IT)
Operation of the over fluxing elements can be inhibited from:
Inhibit 24IT A binary or virtual input.
Inhibit 24DT-n A binary or virtual input.
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