ABB Relion 670 Series Applications Manual page 294

Section 12
Multipurpose protection
12.1.3 Setting guidelines
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 (
power (
GlobalBaseSel : Selects the global base value group used by the function to define IBase , UBase
SBase . Note that this function will only use IBase value.
and
12.1.3.1 Directional negative sequence overcurrent protection
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
NOT 3I2 current; this is essential for proper OC pickup level setting)
3. Set
intentionally inverted in order to simplify directionality
4. Set base current
5. Set base voltage
6. Set
voltage for this angle during the fault)
7. Set
288
When inverse time overcurrent characteristic is selected, the operate time of
the stage will be the sum of the inverse time delay and the set definite time
delay. Thus, if only the inverse time delay is required, it is important to set the
definite time delay for that stage to zero.
SBase ) are set in global base values for settings function GBASVAL.
The overcurrent steps has a
the minimum operate current. Set
achieve ANSI reset characteristic according to standard. If
StartCurr_OCx for any step the ANSI reset works as if current is zero when
current drops below
The function has default setting of operate values and timers according to the
typical application as a power system back up protection. These settings
should be modified according to the system back up protection strategy of
individual utility. The recommended minimum time delay setting of function
should be greater than 0.05 s when used in process bus 9-2 application.
CurrentInput to NegSeq (please note that CVGAPC function measures I2 current and
VoltageInput to -NegSeq (please note that the negative sequence voltage phasor is
IBase value equal to the rated primary current of power line CTs
UBase value equal to the rated power line phase-to-phase voltage in kV
RCADir to value +65 degrees ( NegSeq current typically lags the inverted NegSeq
ROADir to value 90 degree
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IBase ), primary voltage ( UBase ) and primary
IMinx ( x =1 or 2 depending on step) setting to set
IMinx below StartCurr_OCx for every step to
IMinx .
1MRK 511 401-UEN Rev. K
IP15009-1 v2
GUID-F7AA2194-4D1C-4475-8853-C7D064912614 v4
M13088-237 v5
IMinx is set above
M13088-3 v5
Bay control REC670
Application manual