M13088-237 v4
The parameters for the general current and voltage protection function (CVGAPC) are set via
the local HMI or Protection and Control Manager (PCM600).
Common base IED values for the primary current (
IBase
), primary voltage (
UBase
) and primary
power (
SBase
) are set in global base values for settings function GBASVAL.
GlobalBaseSel
: Selects the global base value group used by the function to define
IBase
,
UBase
and
SBase
. Note that this function will only use
IBase
value.
The overcurrent steps has a
IMinx
(
x
=1 or 2 depending on step) setting to set
the minimum operate current. Set
IMinx
below
StartCurr_OCx
for every step to
achieve ANSI reset characteristic according to standard. If
IMinx
is set above
StartCurr_OCx
for any step the ANSI reset works as if current is zero when
current drops below
IMinx
.
10.1.3.1 Directional negative sequence overcurrent protection
M13088-3 v5
Directional negative sequence overcurrent protection is typically used as sensitive earth-fault
protection of power lines where incorrect zero sequence polarization may result from mutual
induction between two or more parallel lines. Additionally, it can be used in applications on
underground cables where zero-sequence impedance depends on the fault current return
paths, but the cable negative-sequence impedance is practically constant. It shall be noted
that directional negative sequence OC element offers protection against all unbalance faults
(phase-to-phase faults as well). Care shall be taken that the minimum pickup of such
protection function shall be set above natural system unbalance level.
An example will be given, how sensitive-earth-fault protection for power lines can be achieved
by using negative-sequence directional overcurrent protection elements within a CVGAPC
function.
This functionality can be achieved by using one CVGAPC function. The following shall be done
to ensure proper operation of the function:
1. Connect three-phase power line currents and three-phase power line voltages to one
CVGAPC instance (for example, GF04)
2. Set
CurrentInput
to
NegSeq
(please note that CVGAPC function measures I2 current and
NOT 3I2 current; this is essential for proper OC pickup level setting)
3. Set
VoltageInput
to
-NegSeq
(please note that the negative sequence voltage phasor is
intentionally inverted in order to simplify directionality
4. Set base current
IBase
value equal to the rated primary current of power line CTs
5. Set base voltage
UBase
value equal to the rated power line phase-to-phase voltage in kV
6. Set
RCADir
to value +65 degrees (
NegSeq
current typically lags the inverted
NegSeq
voltage for this angle during the fault)
7. Set
ROADir
to value 90 degree
8. Set
LowVolt_VM
to value 2% (
NegSeq
voltage level above which the directional element
will be enabled)
9. Enable one overcurrent stage (for example, OC1)
10. By parameter
CurveType_OC1
select appropriate TOC/IDMT or definite time delayed curve
in accordance with your network protection philosophy
11. Set
StartCurr_OC1
to value between 3-10% (typical values)
12. Set
tDef_OC1
or parameter “k” when TOC/IDMT curves are used to insure proper time
coordination with other earth-fault protections installed in the vicinity of this power line
13. Set
DirMode_OC1
to
Forward
14. Set
DirPrinc_OC1
to
IcosPhi&U
15. Set
ActLowVolt1_VM
to
Block
• In order to insure proper restraining of this element for CT saturations during three-
phase faults it is possible to use current restraint feature and enable this element to
operate only when
NegSeq
current is bigger than a certain percentage (10% is
Section 10 1MRK 505 370-UEN D
Multipurpose protection
230 Busbar protection REB670
Application manual
To Next Page
Loading...
Need help?
General
