7SR11 & 7SR12 Description Of Operation
Chapter 1 Page 60 of 88 ©2017 Siemens Protection Devices Limited
3.18 Power Protection: Power Factor (55) – 7SR12
Two power factor elements are provided.
Gn 55-n Setting sets the pick-up power factor of the element.
Under-power factor or over-power factor operation can be set by the Gn 55-n Operation setting.
Gn 55-n 1ph/3ph Power allows the settings to be based on any one phase power factor or the average power
factor of all three phases.
An output is given after elapse of the Gn 55-n Delay setting.
Operation of the power factor elements can be inhibited when:
The measured current is below the Gn 55 U/C Guard setting
A VT Fail condition is detected
Inhibit 55-n A binary or virtual input.
V
1
I
L1
V
2
V
3
I
L3
I
L2
&
Enabled
Enabled
<
&
<
<
&
En.
Inhibit
VT Fail
&
+W
-VAr
-W
-VAr
-W
+VAr
+W
+VAr
Gn55-n: Operation: Under/Over
Gn 55-n U/C Guard
Setting
Gn 55-n Delay
Gn55-n: 1ph/3ph Power
Gn55-n: Dir. Control
Gn55-n: Setting
Gn 55-n U/C
Guarded
Gn 55-n VTS
Action
Gn 55-n Element
55-n
General Pickup
Inhibit 55-n
Figure 3-33 Logic Diagram: Power Factor Protection (55)
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