7SR242 Duobias Description Of Operation
©2010 Siemens Protection Devices Limited Chapter 1 Page 39 of 52
3.11 Voltage Protection: Under/Over Voltage (27/59)
Optionally four under/over voltage elements are provided.
The relay utilises fundamental voltage measurement values for this function.
27/59-n Setting sets the pick-up voltage level for the element.
The sense of the element (undervoltage or overvoltage) is set by the 27/59-n Operation setting.
Voltage elements are blocked if the measured voltage falls below the 27/59 U/V Guard setting.
An output is given after elapse of the 27/59-n Delay setting.
The 27/59-n Hysteresis setting allows the user to vary the pick-up/drop-off ratio for the element.
Operation of the under/over voltage elements can be inhibited from:
Inhibit 27/59-n A binary or virtual input.
27/59-n U/V Guarded Under voltage guard element.
27/59-n U/V
Guarded
Yes
V
or> <
General Pickup
27/59-n
Inhibit 27/59-n
27/59-n Hysteresis
27/59-n Delay
c
27/59-n Setting
27/59-n Operation
<
27/59 U/V Guard
Setting
27/59-n Element
Enabled
Disabled
&
&
Figure 3-18 Logic Diagram: Under/Over Voltage Elements (27/59)
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