P14x
4.2
VOLTAGE DEPENDENT OVERCURRENT LOGIC
V Dep OC Status
VCO I>1
VRO I>1
VAB
V Dep OC V<1 Set
I>1 Current Set
×
V Dep OC k Set
VAB
V Dep OC V<1 Set
I>1 Current Set
VAB
V Dep OC V<2 Set
I>1 Current Set
×
V Dep OC k Set
VAB
V Dep OC V<2 Set
VAB
V Dep OC V<1 Set
V Dep OC k Set
I>1 Current Set
VAB
Figure 40: Voltage dependant overcurrent logic (Phase A to phase B)
The current threshold setting for the Overcurrent function is determined by the voltage.
If the voltage is greater than V Dep OC V<1 Set, the normal overcurrent setting I>1 current set is used. this applies
to both VCO and VRO modes.
If the voltage is less than V Dep OC V<1 Set AND it is in VCO mode, the overcurrent setting I>1 current set is
multiplied by the factor set by V Dep OC k set.
If the voltage is less than V Dep OC V<2 Set AND it is in VRO mode, the overcurrent setting I>1 current set is
multiplied by the factor set by V Dep OC k set.
If the voltage is between V Dep OC V<1 Set and V Dep OC V<2 Set AND it is in VRO mode, the overcurrent setting is
multiplied by a functional operator to determine the setting.
4.3
APPLICATION NOTES
4.3.1
SETTING GUIDELINES
The V Dep OC k setting should be set low enough to allow operation for remote phase-to-phase faults, typically:
I
F
k
=
1 2 .
I
>
P14xEd1-TM-EN-1
&
1
&
&
&
&
Functional
Operator
Chapter 6 - Current Protection Functions
1
Note : This diagram does not show all stages . Other stages follow
similar principles.
Vdep OC Start AB
Applied Current
Threshold
V00644
107