Setting Guidelines - ABB REG670 Applications Manual

1MRK 502 071-UEN -
12.1.3
12.1.3.1
Generator protection REG670 2.2 IEC and Injection equipment REX060, REX061, REX062
Application manual

Setting guidelines

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.
The parameters for the general current and voltage protection function (CVGAPC) are
set via the local HMI or Protection and Control Manager (PCM600).
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.
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 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
Section 12
Multipurpose protection
451